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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 675
Registered: 5-2012
Posted on Thursday, 23 April, 2015 - 02:37 am:   Edit PostDelete PostView Post/Check IP

Hi Folks. I am at a complete loss on the following problem. When I accelerate there is absolutely no power at all. Car runs great on tickover and can be rev'ed no problem in the garage under no load conditions. When I drive off everything seems ok but when I turn onto the main road the car will just not accelerate. I have to lift off the pedal and wait for the engine to catch up.

So far I have checked the compression on all cylinders and they are all around 150 psi. The car has a new coil, points, distributor cap and spark plugs. Leads (copper) were replaced a couple of years ago. The carburetor float levels are ok. I have checked that the accelerator pedal fully opens the carb butterfly valves. The carbs are perfectly balanced. When I remove the carb vacuum chambers and move the jet down I can see the petrol on the jet (is this correct?) so I don't think there's a blockage. I had (until today) had the mixture set correctly. I have checked for leaks on the vacuum pipes. The one that runs to the autobox modulator is good as is the one that connects to the "cruise control" unit. Today, just out of frustration and to see what happens I "adjusted" the jets on both carbs to fully rich. This did seem to improve matters slightly, but is obviously a measure that is compensating this elusive fault. I should add I don't think this is a minor tuning problem. The loss of power is so great it is pointing to something more major than that. Any ideas?

Geoff
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Mark Aldridge
Prolific User
Username: mark_aldridge

Post Number: 205
Registered: 10-2008
Posted on Thursday, 23 April, 2015 - 05:57 am:   Edit PostDelete PostView Post/Check IP

Geoff, this sounds like fuel starvation. If you drive the car very gently, will it reach normal driving speeds? Then if you accelerate hard, does it die ? This would suggest sufficient fuel flow at very light loads, but inadequate for any load.
Mark
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 676
Registered: 5-2012
Posted on Thursday, 23 April, 2015 - 06:28 am:   Edit PostDelete PostView Post/Check IP

Hi Mark

Yes, that's exactly what happens. Also, during the attempt to accelerate phase I do hear a lot of intake hiss, but no accompanying power. The thing is I am fairly sure this is not a float chamber problem. I have removed the covers (simple task in the SY1) immediately after a run and find the fuel is at the correct level. I guess the next step is to rebuild the carbs. The reason I am asking this question is to check I have not missed anything obvious and also to get a second opinion. I find your comments invaluable as they confirm my thinking. One of the reasons I have not already stripped the carbs is the car revs quite happily under no load conditions. I guess it is possible there is a partial blockage in one of the carbs preventing the full amount of fuel getting through when the engine is under load. It appears I have no choice but to rebuild the carbs and then hope this clears the problem. I guess this problem is akin to many on these cars - you just have to keep ruling out possibilities until you hit on the solution.

Many thanks

Geoff
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bob uk
Unregistered guest
Posted From: 92.40.248.194
Posted on Thursday, 23 April, 2015 - 04:37 am:   Edit PostDelete PostView Post/Check IP

Disconnect the exhaust and try

(Message approved by david_gore)
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christopher carnley
Unregistered guest
Posted From: 86.151.188.65
Posted on Thursday, 23 April, 2015 - 04:23 am:   Edit PostDelete PostView Post/Check IP

Blockage in petrol tank pick up, filter blockages, low pump delivery???

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1578
Registered: 4-2003
Posted on Thursday, 23 April, 2015 - 08:01 am:   Edit PostDelete PostView Post/Check IP

Chris +1 - also the filter in the carburettor body.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 678
Registered: 5-2012
Posted on Thursday, 23 April, 2015 - 08:11 am:   Edit PostDelete PostView Post/Check IP

Thanks for the suggestions.

Chris - I have recently changed the carb filters and am currently waiting for the main rear filter to arrive from FS (ordered 9 days ago). As an interim measure I have bypassed the filter. When investigating this problem I found the SU pump was damp with petrol so fitted a modern equivalent. I have run a flexible pipe from the carb end of the fuel pipe and the petrol pumps through at a very acceptable rate. Also I have removed the float covers after running the engine and the petrol level is ok.

Bob. I replaced the entire exhaust about 18 months ago. The replacement came from FS. As for road testing with the exhaust disconnected, I shudder to think. I reckon at least a visit from the police. Worse still, in the US we have housing associations who are worse than the Gestapo. I'm thinking of joining Vladimir in the outback. Oh the joy to park as many cars as you like at your house without being secretly photographed and hassled by the SS stormtroopers of the local housing association.

Geoff.
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Vladimir Ivanovich Kirillov
Prolific User
Username: soviet

Post Number: 233
Registered: 2-2013
Posted on Thursday, 23 April, 2015 - 09:07 am:   Edit PostDelete PostView Post/Check IP

Geoff, I am assuming the fuel filter is new. I would try the car on a bitumen road with the aircleaner disconnected or try a new aircleaner and check nothing like a cat or a rag has taken up residence from the intake to the cleaner. Next drop the exhaust system off and retest - exhaust systems can become blocked over time, its rare but not impossible. Its common problem on chainsaws, motorbikes and lawnmowers but I have seen it on cars but very rarely.

Just a quick aside on evil air filters and fun games to play with loaded handguns while you are drunk and in the dark. I was once employed by a genius, a fully qualified mechanic who had a bus company.

When I joined this firm his star bus had a problem but he was fixing it. On my first day of employment he announced that he was onto the problem. What the bus would do was run while standing still and it would rev while standing still but out of the road would not reach 65 kilometres an hour.

Now this loon had "advanced the concept" by replacing the injectors, the injector pump, the turbo, the intercooler and believe it or not rerouted the induction system to his very own design.

This fellow had more gauges hanging off this engine, testing this and that than an intensive care ward in Switzerland would have on a dying Rock and Roll star. He would get me to drive here and there and buy this and that as his theoretical mind developed bigger and more strange theories as to why the engine would not throw the coach down the road at 110 kilometres and hour. Yes, he was certainly a different breed.

He had also borrowed quite a few million dollars buying Chinese buses the very same model of which broke its chassis in half on a Californian highway with full load of passengers resulting in packs of hungry lawyers with black fins on their backs scurrying around in law firms late at night drawing up legal writs claiming unbelievable amounts of damages.

I put up with him for about 4 months too long. He's bankrupt now, his woman has left him and he sings songs of doom and dread into a large wine flagon somewhere unknown as the banks came after him.

Yes blocked inside air filter - what a mug.

Next I would drain the fuel tank and run the engine until it stops and then refil it with premium octane fuel. Bad fuel is rare but it happens and you can spend hours replacing and checking everything only to find the fuel is crook and its croaked the spark plugs.

I had a boss once, lovely fellow, who sent me a long distance with all type of merry instructions to replace the single carby with twin carbs, pull the distributor etc etc etc. I pulled the spark plugs brought them back to the workshop and tested them and they were stuffed and broke down immediately in the tester. The problem was somebody had stolen the good fuel out of the truck and replaced that petrol with some liquid that coated the ceramic insulators at the bottom of the plugs adjacent to the gap which allowed the engine to run but earthed out the plugs under load. These were brand new spark plugs and so what ever was in the replaced fluid was so nasty that a new set of plugs were essential. And this lunacy had to be dealt with the owner yapping continually in my ear "it can't be the petrol for God's sake listen to me, it can't be the petrol are you @%##ing listening to me"

Sometimes owners need to be gaffer taped to solve the problem. Farmers are the worst because they have a little bit of know how. One farmer drove me crazy trying to tell me my job and making it clear he didn't have faith in me at all only to drive into the workshop a week later and declare his 1960's International V8 truck has never flown so fast and blah blah.

The important thing to remember when you are faced with a curly one like this is when your patience has totally run out and you are right on the edge of insanity, you just have to be logical and realize the engine is not performing because you have not found the problem.

Also, a new set of ignition points can be the problem especially if nobody has lubed the cams on the distributor drive shaft. What happens is the edge on the points that comes in contact with the cam has been ripped off closing the point gap and throwing the engine timing way out.

Another but unlikely caper is the distributor drive shaft gear has lost a tooth or the drive pin if it has one has sheared, again throwing the timing out.

Considering the engine is running metal timing gears from crankshaft to camshaft its unlikely that is the problem. Some engines use a fibre gear to drive the camshaft ie early grey and red Holden engines, the fibre gear strips but it usually stops the engine completely. I had one do this right in the middle of the nullabour plain about 1000 miles away from any city I could buy another timing gear. This was a fully reconditioned engine but admittedly I had driven it for 36 hours non stop. I replaced the timing gear and it would not start. Another strip down of the engine revelled the camshaft had broken into two pieces ! Ho what fun.

Get your ohms tester out and check each of the leads for resistance. Eyeball the distributor rotor button for cracks too. The silliest thing about rotor buttons I ever came across was on an Ford F100 Ambulance/camper van a biker mate of mine had. This chap had 7 Moto Guzzis and a beard. He had installed this rotor button and it was from a different model and instead of being firmly secure to the top of the distributor shaft this thing could be turned almost 45 degrees freely and yet the engine still ran. I punished my mate by consuming some kangaroo road kill with him that we picked up warm that morning and by getting him so horrifically drunk, that I was able to get him screaming crazily by convincing him the government had just introduced safety belts rules for all motorbike riders. Rotor buttons can have a mircoscopic crack that causes the ignition system to break down underload. Lucas black rotor buttons lead the world in this type of fun.

Beware the new distributor cap. I have seen two problems here, the first being the new distributor cap is not right model and the locating lug is in a different place again that throws the timing out, the second problem is (and this is very easy to do) the wires are in the wrong holes so look at the book, identify where number one lead is in reference to the vacuum diaphragm, know the rotation direction of the rotor and check that each lead is in the right position using the engine firing order and that each lead is going to the cylinder it should be going to.

Furthermore, check the vacuum advance diaphragm is not perforated buy sucking on a tube going straight to it. You can check the mechanical advance and the vacuum advance are within spec with a timing light. Porsche came up with the amazing concept of checking the timing only at 6,000 rpm which I thought necessitated the dropping of at least two valium pills beforehand because when you are close to a flat 6 spinning at six thousand revs the noise is something else and there is an inherent paranoia about what would happen to the chest area if and when one of the fan blades came in your direction.

The rotten mongrel of the fault is there Geoff and when you find it let us know what it was.

One day far into retirement I will scribe a book titled "The Book of Mechanical Geniuses - a True But Foul Memoir"

Good luck
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Vladimir Ivanovich Kirillov
Prolific User
Username: soviet

Post Number: 234
Registered: 2-2013
Posted on Thursday, 23 April, 2015 - 11:23 am:   Edit PostDelete PostView Post/Check IP

Geoff, I made the mistake of not reading all the entries by the other jetsetters before my last screed, sorry about that.

I have found that democracies decrease dramatically in democratic life the closer they are to the big cities. Democracy increases and actually still exists in outback Australia.

Your SS Stormtrooper local housing association people would have a life expectancy that could only be estimated in the scale of nanoseconds out here. The only regret I have had in 7 years of outback life is that I didn't have to opportunity to do it when I was younger due to the fact that I always had a female attachment who while never failing to suck on the purse dementedly had the accompanying skill of producing zero income.

I can actually physically feel my freedom being sapped away when I travel down to towns on the coast where I can get a jet to Brisbane for overseas adventures. There are cameras everywhere, police everywhere, crime everywhere and loon behaviour blatantly evident. Needless to say my anxiety level goes up.

When I drive to the local pub in my town in my 1976 Cadillac Fleetwood tourists travelling through stop drinking and start gawking. When I tell them that I would have brought the Rolls but its not going they shudder in total disbelief.

We have not had any crime in this town since November 1918. The government made the mistake of crossing Tom Coolon who this town was named after. Tom came into town and shot four men dead he suspected were guilty of assisting the government by taking his gold mining lease from him. Arguments still exist today amongst historians and the public as to whether Tom escaped to the USA or shot himself. The police removed themselves from town permanently in 1967 and the fellow I bought my place from told me the police 124 kilometres away are only interested in coming to town for crimes such as manslaughter up.

The roads to town however are murderous and quite a few people get maimed or killed every year and those who call for help on the mobile phone find they have zero coverage. Its a hoot Geoff it a hoot.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 679
Registered: 5-2012
Posted on Thursday, 23 April, 2015 - 02:01 pm:   Edit PostDelete PostView Post/Check IP

Hi Vladimir

Thanks for all that great information. Happily, I can say I have covered off most things you have mentioned but one glaring possibility stands out. The air filter. When I balanced the carbs the unisyn carbalancer I use requires the U shaped air ducts be removed from the mouths of the carburetors. I balanced the carbs and when I re-attached the air inlet ducts I was careful to note any change in engine revs. There was none, so I assumed the air filter was ok. However, in light of what you have written it occurs to me I have not tested the air filter with the engine under load. Tomorrow I will test the car with the main air duct (elephant's trunk) removed.

Going through the other points you mention:

I have bypassed the main fuel filter - I am awaiting a new one from Flying Spares. The filter bowl was remarkably clean. The carb filters were replaced a few months ago.

I'm pretty sure the fuel is fresh. I ran the tank right down a couple of weeks ago and siphoned off the remaining petrol to facilitate replacement of the fuel pump. Although I then re-used the petrol it was mixed with a further 10 gallons of fuel when I filled up at the petrol station. The original fuel was not old in any case, so I can rule this possibility out.

Spark plugs, distributor cap, rotor arm and coil were replaced a few weeks ago. A new set of points fitted yesterday. Leads are copper and were replaced a couple of years ago. The only thing I am doing that is non standard is running a 12v coil without the ballast resister. In theory this may cause the points to get pitted faster than normal as the condensor may be out of balance, but I cannot imagine this would cause such a loss of power on acceleration. The reason I am running this system is I intend to fit pertronix electronic ignition soon.

The exhaust system is new from about 18 months ago. I drove the car for a couple of years in Nevada and for the last 6 months in Florida. Neither state has harsh winters so no salt to rot the exhaust super quick. I would not expect the exhaust to have failed so soon, but will bear this possibility in mind if all else fails.

I'm thinking this problem is fuel related. If the air filter test tomorrow doesn't give a good result I will rebuild the carbs.

Re: the SS Stormtroopers

We used to rent a house in Las Vegas. One day I was working on the Rolls in the garage with the doors open due to the 100+F summer heat. I noticed a car had pulled up at the bottom of the driveway and the driver was sneakily taking photos. A few days later I got a letter from the housing association telling me I was contravening the rules and if I did it again I would be fined $100. It felt like the KGB were monitoring me. We have just moved back to our house in Florida and since we own it we have to pay the local housing assoc $450 a year for the pleasure of having them hassling us whenever they feel like it. When we move I am definitely not going to buy a house with a housing association. When we first moved here in 2004 our accountant lived 40 miles outside Tampa in a non housing assoc road. His driveway had several classic cars parked on it. So much more civilised than having to put up with the rantings of the KGB. There are housing estates in Vegas for the over 55's. They are so rigorously managed the homeowners are not even allowed to park their cars on the driveways, they have to be garaged with the doors closed. The houses are immaculate with carefully manicured lawns, but these estates are completely devoid of any life. They are totally sterile. My wife said people come here to die. I reckon they are dead already.

Regards

Geoff
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John Kilkenny
Prolific User
Username: john_kilkenny

Post Number: 190
Registered: 6-2005
Posted on Thursday, 23 April, 2015 - 04:45 pm:   Edit PostDelete PostView Post/Check IP

You are seriously overloading a seven volt coil with 12 volts. This can affect the circuit recovery time. Replace the ballast resistor.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 938
Registered: 9-2004
Posted on Thursday, 23 April, 2015 - 05:18 pm:   Edit PostDelete PostView Post/Check IP

"replace the ballast resistor."

Or do away with it useing a 12v coil, ok if all other electrics are a 100%.

I do wonder how many folk change to electronic ignition leaving the 8v coil in place.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 939
Registered: 9-2004
Posted on Thursday, 23 April, 2015 - 05:20 pm:   Edit PostDelete PostView Post/Check IP

Sprag u/s maybe.
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Mark Aldridge
Prolific User
Username: mark_aldridge

Post Number: 206
Registered: 10-2008
Posted on Thursday, 23 April, 2015 - 06:45 pm:   Edit PostDelete PostView Post/Check IP

Geoff, further thoughts; have you checked fuel filters on the carbs and have you checked pump delivery ? I note the pump is new, but that sadly is no guarantee !
Mark
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Bob Reynolds
Prolific User
Username: bobreynolds

Post Number: 249
Registered: 8-2012
Posted on Thursday, 23 April, 2015 - 08:34 pm:   Edit PostDelete PostView Post/Check IP

Sorry for stating the obvious, but have you got any oil in the carb dashpots?

This provides the enriched mixture needed for acceleration, which is what you seem to be lacking. Although it's not usually as serious as the symptoms you mention.

This is the first thing I would check.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 680
Registered: 5-2012
Posted on Friday, 24 April, 2015 - 12:23 am:   Edit PostDelete PostView Post/Check IP

Hi Folks

As always, many thanks for the ideas and suggestions.

John and Patrick - The coil is a 12v coil. A few months ago I fitted Powerspark electronic ignition with a new 12v coil and removed the ballast resister. Worked great for a month when the Powerspark module failed. As an interim I refitted the original points with a view to fitting a Pertronix system. This has been delayed by the appearance of this new fault. The points I refitted were quite pitted so last Monday I replaced them with a new set that had just arrived from FS. I know these may wear quicker than normal due to the higher voltage and "wrong" condensor, but I do not believe they are the cause of such a major problem with the engine. I will of course fit a Pertronix system as soon as I have resolved the current issue.

Patrick - If the sprag was u/s I think the engine would just rev high with little or no drive. In my case, the engine revs fade until I lift off the accelerator pedal.

Bob - the dashpots have oil to the correct level. I'm using standard 10-40 engine oil.

Mark - I have bypassed the rear fuel filter as I am awaiting delivery of a replacement from Flying Spares. The carb filters were replaced a couple of months ago. I did look online to see if I could buy a pressure gauge for the fuel line but they were all designed for fuel injected lines that run at much higher pressures. I did run a flexible hose from the end of the fuel pipe that connects to the carb farthest from the fuel tank and found the pumping rate to be very acceptable. It half filled a gallon receptacle in less than a minute. I have also removed the float covers immediately after a test run and found the petrol levels to be ok. I do take your point though. Once a system is under load it can behave very differently to the "static" tests I have carried out. It is entirely possible that as I try to accelerate the fuel level is dipping in the float causing the fuel starvation. I will revisit this area once I have ruled out other possible causes.

Regards

Geoff
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Jim Walters
Experienced User
Username: jim_walters

Post Number: 33
Registered: 1-2014
Posted on Friday, 24 April, 2015 - 04:14 am:   Edit PostDelete PostView Post/Check IP

Geoff, 99% of the time the fault you described is the symptom of a faulty coil, condensor, rotor, or points. It is characteristic of an ignition fault that an engine will rev fine without load but under load will not. Even though the coil is recent plug another one in. You do not have to go to the trouble of bolting it in place of the one currently installed, just lay it on top of the engine and connect the wires. This will instantly eliminate the coil as the problem if the symptoms are the same. By the way, we won't use coils made in China. I've had two dead right out of the box. These are supplied from a well known name brand vendor, Standard Motor Products. Their coils made in USA or Mexico have been fine in our experience but check the actual coil inside the box for country of manufacture before you buy it. Next, take the coil lead and hold the cap end within an eighth of an inch of the centre of the rotor arm. With the ignition on, make and break the points with an insulated screwdriver, if a spark jumps from the coil lead to the rotor the rotor is dead shorting and can cause the symptoms you are experiencing. Replace it. Holding the coil wire end close to ground and observing the spark will also tell you something. Yellow spark - weak coil, condensor, low voltage to coil. Blue spark - coil, voltage, condensor probably OK - points, cap, rotor, plugs or leads suspect. Next, check the points gap, preferably with a dwell meter. If the dwell (points gap) is not close to specs the coil does not get enough saturation time to fire efficiently. Rectify the dwell if not within 26 to 28. Lastly, replace the condensor. They are fairly often bad right out of the box, and can go bad at any time after installation. They are an age sensitive part, and no one knows how long it has sat on a shelf somewhere before you bought it. I've had Lucas ones as well as aftermarket ones bad right out of the box. These tests are the ones we do in order as a combination of most likely and easiest to do. These tests are useful if one does not have access to a scope or coil tester. If you don't have a dwell meter just make very sure the points gap is set at .014 to .016 thou. A dwell meter is preferable though as it is more accurate. Do not assume that your coil or condensor are good just because you recently replaced them, this assumption has led some to many hours of needless searching for a solution to a fault.


SRE22493 NAC-05370
www.bristolmotors.com
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Mark Aldridge
Prolific User
Username: mark_aldridge

Post Number: 207
Registered: 10-2008
Posted on Friday, 24 April, 2015 - 06:06 am:   Edit PostDelete PostView Post/Check IP

Geoff, I think you have ruled out fuel, therefore I am suggesting condenser as this would account for the old points burning and a weak spark. Jim's advice and test sequence would be my next approach.
Mark
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 681
Registered: 5-2012
Posted on Friday, 24 April, 2015 - 06:58 am:   Edit PostDelete PostView Post/Check IP

Jim and Mark

I will be taking your advice. This will be my next step, hopefully tomorrow but definitely this weekend. I will report back.

Regards

Geoff
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Vladimir Ivanovich Kirillov
Prolific User
Username: soviet

Post Number: 238
Registered: 2-2013
Posted on Friday, 24 April, 2015 - 09:07 am:   Edit PostDelete PostView Post/Check IP

Geoff, the scribes that say look at the condenser may be onto something. There are three tests to run on a condenser but I have forgotten all of them due to my experience of never having to replace one since 1972 and the only one I tested was the one in the Tech School on the odd day I attended when I was not pulling a sicky to hit the booze/and or chase girls with all my other questionable young travellers - well it was the 1970's.

Also, when you fitted the new ignition points did you clean the protective coat off the faces with petrol/gas before fitting ? That coating can provide a bad contact if not removed.

I would like to know what were the last three things you did to the car just prior to it developing this problem. Very often the history of what was done is important to diagnois the mongrel fault - bosses these days run around with stop watches and think in milliseconds in order to make a buck out of the trade.

And I certainly have came across new electric parts from China that look nice and shiny but simply do not work. That was unheard of in the 1970s when Bosch and Delco were the king billies.
Now if one is sent the right part (and there is ratio of one to three it will be the wrong part) you definitely can't assume that part will work. This is so if the part is made with the magic words "Made in China" or sneakily has no marking on the packet or part as to its origin.

Whilst I am on a roll here giving my northern very populated friends a royal serve I should say that with complete amazement about 5 years ago I bought a 98 piece spanner set at the local hardware that was so cheap (I forget the actual price but remember is was very very cheap) that I was certain that these spanners were total crap. They are marked "Chrome Vanadium" and were definitely made in China. Sadly, the company making them never used a name anywhere on the spanners or the folding packet. Incredibly they are of Snap-on quality and I have given them some very vicious treatment over those years in order to make a buck.

My experience with mechanical repairs is that Murphy's law always applies. Often while doing a repair and replacing this or that item, the repairer makes a mistake but does not know about it. This happens in the trade very often and is a cause of much anxiety leading to many mechanics giving up fixing even their own cars and going straight into truck driving.
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John Kilkenny
Prolific User
Username: john_kilkenny

Post Number: 191
Registered: 6-2005
Posted on Friday, 24 April, 2015 - 11:42 am:   Edit PostDelete PostView Post/Check IP

Geoff,
Firstly my apologies for not properly reading your post.
With a points system, using a 12 volt coil without a ballast resistor will not produce excessive pitting, though it could affect ease of starting.
You should check that the condenser is connected properly, also that the dwell angle and points gap are within limits. Any of these being wrong can give symptons similar to what you are experiencing.
Good luck !
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 683
Registered: 5-2012
Posted on Friday, 24 April, 2015 - 12:44 pm:   Edit PostDelete PostView Post/Check IP

Vladimir - I agree, the fault is most likely related to a recent change I made to my car, namely fitting electronic ignition. The electronic module failed so I refitted points but still used the new 12v coil I had bought. Tomorrow should be interesting. I will refit the original coil and ballast resister. If it works, then I will be a convert to Brian Vogel's, and more latterly Patrick Lockyer's maxim - if it ain't broke, don't fix it.

John - The distributor is set up ok - I have a good quality timing light that also measures dwell angle, which is currently set at 27 degrees. So no problem there. It will be really interesting to see if refitting the original coil and ballast resister cures this fault. I quite like the idea of running a 12v coil because of the high HT output, especially in light of what you have written. However, if I can get the car fully operable again I think I'll leave the "upgrades" for a while and just enjoy driving the car again.

Regards

Geoff
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David Gore
Moderator
Username: david_gore

Post Number: 1582
Registered: 4-2003
Posted on Friday, 24 April, 2015 - 09:17 pm:   Edit PostDelete PostView Post/Check IP

Vladimir,

Chrome-Vanadium steel [SAE6150] has a special benefit in that it can be easily hardened by two different heat treatment processes to give a wide range of properties to suit particular applications. The first is conventional quench and tempering to give a hard wear-resistant high strength steel and the second is austempering which gives a very useful combination of strength and toughness [impact resistance].

Australian members will be aware of the traditional Sidchrome spanners that are highly sought after by the Saturday garage sales and farm clearance sales buyers for their longevity and resistance to abuse. These were made from austempered SAE 6150 steel and could be put into a vise and hammered to a 90 deg right angle without breaking whereas a quenched and tempered equivalent would fracture after a 10/15 deg bend.

Certain low-cost overseas manufacturers claim Chrome-Vanadium on their products to "piggy-back" on the Sidchrome reputation but fail the vise bend test as they are quenched and tempered rather than austempered to match the original Sidchrome product. My Sidchrome spanners and socket set are as good today as they were when I purchased them 50 years ago despite much use [and abuse in applications other than their intended use].

It is possible the spanner set you referred to was a set made in Taiwan to Sidchrome specifications after Stanley Black & Decker acquired Sidchrome in the mid-1990's, ceased production in Australia and transferred production to Taiwan.
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gordon le feuvre
Frequent User
Username: triumph

Post Number: 72
Registered: 7-2012
Posted on Friday, 24 April, 2015 - 10:05 pm:   Edit PostDelete PostView Post/Check IP

Geoff, i cannot see any mention of the carb emission weakener system. This is designed to put partial vacuum on top of fuel in floats to counteract atmospheric pressure. If too much vacuum, this will "hold" fuel in float chamber even when air is rushing over jet. If you read manual, there is a cap (on top of "A" bank (righthand from driver's seat) that can be removed
and left off to roadtest. it's worth a try!! this is the sampling point take off to check readings with manometer.
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Randy Roberson
Grand Master
Username: wascator

Post Number: 372
Registered: 5-2009
Posted on Saturday, 25 April, 2015 - 12:21 am:   Edit PostDelete PostView Post/Check IP

Ignition in bad condition and also a collapse or other exhaust system malady which partially blocks the exhaust. Just two places I would look first, but in the order mentioned, considering what you have checked already.
Ditto the faulty new parts; we see it frequently even with parts for industrial equipment.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 684
Registered: 5-2012
Posted on Saturday, 25 April, 2015 - 01:28 pm:   Edit PostDelete PostView Post/Check IP

Hi Folks

I re-fitted the original coil and ballast resister today, in place of the suspect 12v coil. Unfortunately the fault is still there. The only suspect part now is the condenser. I have ordered one from FS but it will be at least a week before it is delivered. In the meantime I will run some additional tests, including the one Gordon suggested above.

I checked Brian's and Larry's resource files but it appears there is no easily available substitute for the condenser . If any one knows of one I would be grateful to hear of it - would save me a week's+ wait.

Regards

Geoff
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christopher carnley
Unregistered guest
Posted From: 86.182.237.235
Posted on Saturday, 25 April, 2015 - 07:42 pm:   Edit PostDelete PostView Post/Check IP

Geoff,
You can fit any "look alike" capacitor, 0.18-0.25 mfd, (uF, microfarad).

(Message approved by david_gore)
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Jim Walters
Experienced User
Username: jim_walters

Post Number: 34
Registered: 1-2014
Posted on Monday, 27 April, 2015 - 05:34 am:   Edit PostDelete PostView Post/Check IP

Geoff, the condensor for your Shadow is exactly the same as the one used in MGB's up to about 1974, about $4 at Moss Motors for a Lucas one. Your local auto parts store probably has one but it may not be Lucas in which case I would recommend against using it.

SRE22493 NAC-05370
www.bristolmotors.com
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christopher carnley
Unregistered guest
Posted From: 86.181.212.56
Posted on Monday, 27 April, 2015 - 05:58 pm:   Edit PostDelete PostView Post/Check IP

A lot of parts marked "Lucas, are not up to the standard of the original Lucas.

(Message approved by david_gore)
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1286
Registered: 6-2009
Posted on Tuesday, 28 April, 2015 - 12:56 am:   Edit PostDelete PostView Post/Check IP

Christopher Carnley wrote, 'A lot of parts marked "Lucas, are not up to the standard of the original Lucas.'

There's a thought that should strike terror into the hearts of British car owners everywhere!

Craig Bolton (who actually worked on my Jag when its fuel pump died during a trip to Pittsburgh) said it most brilliantly with his NOS Lucas Replacement Wiring Harness Smoke Kit.

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 685
Registered: 5-2012
Posted on Tuesday, 28 April, 2015 - 05:25 am:   Edit PostDelete PostView Post/Check IP

Hi Folks

Chris - Thanks for the giving the values of the capacitor. I did try to match one from Napa auto parts but they give sparse details of the specs of their condensers.

Jim - I checked out the autozone website and found they did list a condenser for 70's MGBs. The part number is LU506 and was stocked locally. It is manufactured by Duralast, not Lucas (i.e. made in China). Though I normally would not go against a professional's advice, I was too curious to see what the effect would be if I bought and fitted one, so I did just that. It has made a massive difference. I still get a flat spot when accelerating but the engine no longer dies forcing me to drive home on low revs. I think the flat spot is because the car is now tuned to try and compensate for a leaky condenser. I will obviously rectify this.

The substitute condenser, LU506 is the same size as the original physically but there are no markings on the case to give any specs. Since I do not have a capacitance meter I cannot say whether it falls within the range mentioned by Chris. Since the original condenser was only failing under load I carried out a no-load comparison with the substitute, by charging both and measuring the discharge using a voltmeter. Both were discharging at 150 mV. I don't know whether this means much, but the fact the readings were the same (within 2 mV) did give me confidence.

I shall be fitting the Lucas condenser I ordered from FS last Friday, just as soon as it arrives.

As a footnote, I came across this on the MGB website: "There is an old maxim - 90% of carburetor faults are electrical."

As always, many thanks for your help.

Geoff
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Mark Aldridge
Prolific User
Username: mark_aldridge

Post Number: 208
Registered: 10-2008
Posted on Tuesday, 28 April, 2015 - 06:59 am:   Edit PostDelete PostView Post/Check IP

Geoff, the only thing one can guarantee is that if you search for an electrical fault first, the problem will be fuel and vica versa !
At least you have now solved the problem
Mark
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Bob Reynolds
Prolific User
Username: bobreynolds

Post Number: 250
Registered: 8-2012
Posted on Tuesday, 28 April, 2015 - 08:05 am:   Edit PostDelete PostView Post/Check IP

You might find this of interest:

http://www.distributordoctor.com/distributor_condensers.htm

I get all of my distributor components from Distributor Doctor. After experiencing problems with modern Chinese rubbish, I won't trust anything else. Points, condensers, rotor arms, they're all dodgy.

Don't take any notice of 'Lucas' printed on the box. It means nothing now, except that it's a Chinese copy of a Lucas part!

The last time I ordered from DD, he still had stocks of the original genuine Lucas components for RR distributors.

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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1371
Registered: 6-2006
Posted on Tuesday, 28 April, 2015 - 09:26 am:   Edit PostDelete PostView Post/Check IP

Geoff,

Did this power loss happen suddenly?

not sure what year your car is but have you tried disconnecting the weakener system to the float chambers? (if yours has it) Rubber hoses the the lids?

Have you tried adjust the ignition timing about 5 degrees either way and see if things change?

(The original; Manual settings are wrong for unleaded fuel.)
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bob uk
Unregistered guest
Posted From: 92.40.249.62
Posted on Monday, 27 April, 2015 - 11:55 pm:   Edit PostDelete PostView Post/Check IP

It is remotely possible that a relatively new exhaust system has turned a baffle over. Disconnect at the first box olive joint or loosen to allow massive leak. This could be done away from home so as not to annoy the neighbours.

Many years ago I had a ford fiesta do the same because the exhaust system was 20 complete we fitted a new one and problem solved.

(Message approved by david_gore)
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 686
Registered: 5-2012
Posted on Wednesday, 29 April, 2015 - 03:02 am:   Edit PostDelete PostView Post/Check IP

Hi Paul

Replacing the condenser has made a huge difference. I still get a flat spot on acceleration but I'm hoping re-tuning the engine should sort this. I note your point on adjusting the ignition timing and will take this into consideration when I re-set it.

Bob - Thankfully it appears the fault is not exhaust related.

Regards

Geoff.
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Bob Reynolds
Prolific User
Username: bobreynolds

Post Number: 251
Registered: 8-2012
Posted on Wednesday, 29 April, 2015 - 06:21 am:   Edit PostDelete PostView Post/Check IP

"(The original; Manual settings are wrong for unleaded fuel.)"

Any idea what the correct settings are, as presumably we are all now running on unleaded fuel, and on the wrong settings.
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1372
Registered: 6-2006
Posted on Wednesday, 29 April, 2015 - 06:30 am:   Edit PostDelete PostView Post/Check IP

Bob, I'll find the recommended settings sheet.

I'm sure it's in the technical library somewhere.

Roughly 5 de3grees more advanced from memory.

(The leaded fuel burns much faster than unleaded fuel. This means that unleaded fuel needs to be ignited earlier so it is at it's peak at TDC ready to push the piston down.
This slower burning flame front also means that the heat has more time to transfer to the surrounds and why better valves are needed on many cars. Luckily are valves are tough enough as standard.)
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 1255
Registered: 5-2012
Posted on Tuesday, 31 May, 2016 - 09:53 am:   Edit PostDelete PostView Post/Check IP

In view of a similar problem on another thread I just wanted to wrap this thread up, as I should have done at the time.

The main fault that so eluded me was the coil. Fitting a new condenser really helped, but it was the coil that cured things. The reason I did not replace it in the first place was because it was quite new and was convinced at the time that it could not be responsible.

Geoff
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Jim Walters
Frequent User
Username: jim_walters

Post Number: 81
Registered: 1-2014
Posted on Tuesday, 31 May, 2016 - 10:09 am:   Edit PostDelete PostView Post/Check IP

I told you so

SRC18015 SRE22493 NAC-05370
www.bristolmotors.com
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Christian S. Hansen
Prolific User
Username: enquiring_mind

Post Number: 192
Registered: 4-2015
Posted on Tuesday, 31 May, 2016 - 10:26 am:   Edit PostDelete PostView Post/Check IP

Given this evidence of the propensity of electrical components to crap out without warning and irrespective of age (i.e. "alive today, dead tomorrow", or "worked fine yesterday, but now broken")...sometimes straight out of the box...is there a way to actualy test, or must any such test be done under operating conditions, not simply on the bench? Without a test, simply replacing with a "known good" part is not entirely reliable, since "known good" is unpredictable, and cannot be equated simply with a "new" one out of the box, or "because it worked last time".
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1922
Registered: 6-2009
Posted on Tuesday, 31 May, 2016 - 11:38 am:   Edit PostDelete PostView Post/Check IP

No, replacing with "known good" parts is not 100% reliable but, then again, nothing is.

Unless you've got something wrong in a system that's a part killer for the "known good part" (which can happen), the probability of a known good part going bad at the very moment it's being used as a diagnostic substitute is a very, very low probability.

I'd certainly be inclined to go this route before ever considering any form of bench testing that is elaborate in nature.

As I've said before, there is the possible and the probable, and I'll rely on the probable before concerning myself with the possible, but remotely possible.

Brian, who's been successful with the "replace with known good part(s)" technique on more than one occasion - as has every mechanic I know
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Jim Walters
Frequent User
Username: jim_walters

Post Number: 82
Registered: 1-2014
Posted on Tuesday, 31 May, 2016 - 11:46 am:   Edit PostDelete PostView Post/Check IP

As far as coils and condensors go, yes. But you need this test box.You can check coils on the bench or on the car. I always test a new coil before installing it. I've had this box almost 40 years and it still gets used often. Removes the guesswork.


SRC18015 SRE22493 NAC-05370
www.bristolmotors.com
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Randy Roberson
Grand Master
Username: wascator

Post Number: 675
Registered: 5-2009
Posted on Tuesday, 31 May, 2016 - 12:02 pm:   Edit PostDelete PostView Post/Check IP

"There; I fixed it!"
Bravo!
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Christian S. Hansen
Prolific User
Username: enquiring_mind

Post Number: 193
Registered: 4-2015
Posted on Tuesday, 31 May, 2016 - 02:18 pm:   Edit PostDelete PostView Post/Check IP

So...it was the coil after all? Seems like there is an object lesson here tied in with the apparent plethora of either defective, or not very long lived, non-OEM replacement parts available on the market. In addition to the "if the customer says the problem is not A, B, or C because they have already checked those items, the first things to check are A, B, and C" strategy, the same applies to "it can't possibly be A, B, or C because I just replaced them recently". The lesson is: before going any further, check A, B, and C and eliminate the obvious "can't possibly be..." things first. As is often, or at least sometimes, the problem, the simple things can cause the most difficulty in terms of diagnosis due to those pre-conceived notions of "it can't possibly be...! I am also guilty in this regard. Years ago I had an electric clothes dryer service call out (not working), only to find that it was not plugged into the electric outlet! Oh, the shame of it!
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John Beech
Prolific User
Username: jbeech

Post Number: 273
Registered: 10-2016
Posted on Saturday, 01 April, 2017 - 03:05 am:   Edit PostDelete PostView Post/Check IP

Jim,

I've bought what looks to be the same thing as your Snap-On MT-640 coil and condenser tester but made by Hartman, instead. Cost me $20 but it's described as not working. I took a flier on buying it in hopes I can repair it because it looks like 1950s technology, e.g. made to to be fixed instead of thrown away. It'll be next week before I have it in my hands to inspect whether I purchased a pig in a poke ;>)
Hatman Coil And Condenser Tester1
- Hartman Coil And Condenser Tester1
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Jim Walters
Frequent User
Username: jim_walters

Post Number: 98
Registered: 1-2014
Posted on Saturday, 01 April, 2017 - 04:12 am:   Edit PostDelete PostView Post/Check IP

Good score John. If not working it will probably be the vibrating contacts inside. Take the box apart, and inside you will see a ball of foam rubber tied around some wires. Take the foam off and you will find a little points mechanism. Clean it up and file the points clean. The other fault occurs when a rookie hooks up the wires incorrectly and fries the wires. Easy fix just replace the melted wires.

SRH8505 SRC18015 SRE22493 NAC-05370
www.bristolmotors.com
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ross kowalski
Grand Master
Username: cdfpw

Post Number: 338
Registered: 11-2015
Posted on Sunday, 02 April, 2017 - 10:45 pm:   Edit PostDelete PostView Post/Check IP

For everyone, what a great thread.

I know several really good "It CAN'T be the X because Y" stories and some them I didn't even do myself.

I just got back from a trip and am going to be installing a new geared started on the RR this AM so no new stories from me, but thanks to all for a great reading over morning coffee. Tons better than the news lately.

Vlad,

"it can't be the petrol for God's sake listen to me, it can't be the petrol are you @%##ing listening to me"

Answer ..... "No"
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Randy Roberson
Grand Master
Username: wascator

Post Number: 725
Registered: 5-2009
Posted on Thursday, 01 June, 2017 - 04:37 am:   Edit PostDelete PostView Post/Check IP

Great thread: I pushed a Range Rover off the highway a couple years ago; lady driver said, "I don't know what happened; it just quit. I do know that I am NOT out of gas, as it says "20 miles to empty" on the dash."
It was out of gas.

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