| Author | Message | ||
     Mark Taxis Frequent User Username: mark_taxis Post Number: 83 Registered: 4-2007 |
I am having electrical problems with the car, It starts and runs beautifully, but once it gets hot and after a longish run (about 40 mins) is suddenly looses power and coughs an splutters, with no power, it will idle ok but as soon as you try to accelerate is coughs, pops and dies rendering the car pretty well un drivable, once it cools off a bit it runs OK for a while,then the problem starts again. I have swapped the coils and that did not change anything, so now I am thinking of replacing the silicon plug leads, are these better than copper leads? Any advice warmly received | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 180 Registered: 4-2015 |
Mark... Others have reported similar problems eventually traced to the rotor. I forget the explantion of the reason, but apparently they can get defective and cause such intermittent running problems. I, too, once had a prewar car that would idle fine but exibited those coughing, non-running, no power symptoms upon any accelration. It could hardly pull itself forward from stationary, but idled fine, and the engine would rev fine in neutral, but no power in gear. New rotor and problem gone. P.S. On the above post: Double check on my memory...upon reflection now I am not so sure if it was the rotor, or the carbon plug and spring gizmo that is inside the distributor cap that in the end resolved the issue. Like you, I fussed with a bunch of things and I could be in error as to which was the final solution, but am pretty sure it was one of those two items, rather than condensor, coil, wiring, points, etc. At least worth checking out. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 72 Registered: 1-2014 |
Most likely coil or condensor in my experience. If you've replaced the coil was it a new or known good one? If yes then condensor. Plug leads will most likely not be the problem. Could be rotor but they will usually exhibit symptoms even when cold. Test rotor by holding coil lead 1/8th inch away from centre of rotor (with cap off obviously) and have someone crank over the engine. If a spark jumps to the rotor it is shot. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| christopher carnley Unregistered guest Posted From: 109.148.48.223 |
Fuel supply problems, cracked distributor cap, exhaust blockage? (Message approved by david_gore) | ||
| Martincweb Unregistered guest Posted From: 213.121.20.207 |
Mark, further to my reply, my MK VI has been fitted with good quality copper core leads. I believe these are more than adequate for these vehicles under normal running conditions. Martin Webster B88HR (Message approved by david_gore) | ||
| Martincweb Unregistered guest Posted From: 213.121.20.207 |
I must admit my B88HR suffered from the same symptoms several years ago. After changing virtually all the ignition components, it turned out to be the ignition harness. Replaced the leads and plug caps and the car was transformed. Martin Webster B88HR (Message approved by david_gore) | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 84 Registered: 4-2007 |
Hi Everyone Thank you all for the feedback. I think I have resolved the problem; there were a number of obvious faults 1. Points out of adjustment and badly pitted, renewed. 2. Battery was totally stuffed, replaced with new. 3. Cleaned plugs and reset gap. 4. Cleaned and checked all ignition and plug leads, some poor connections rectified. 5. Cleaned and checked distributor. 6. Checked static timing and adjusted. 7. Added new 95 octane fuel. By the by, my car is fitted with single points, distributor was modified with a 6 cam shaft, now accepts $10 points from a Holden Gemini. The rotor cap is also different in that it does not have what looks like a fuse in the cap as fitted to the original rotor. Car is running smoothly and starts so much better, fingers crossed there are no further issues | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 73 Registered: 1-2014 |
FWIW you can test carbon core plug leads with a DMM, they should show 10,000 ohms to 20,000 ohms per foot of lead length. Copper leads should measure zero ohms no matter the length. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 85 Registered: 4-2007 |
The same problem has just re occured I have just driven for 2 hours, the car has gone up and down hill, along the highway for 15mins at 60 mph ,a couple of stops and restarts at the shops and no problem. Just as I was approaching home up a fairly steep and twisty road it started to lose power, cough and splutter, easing off on the accelerator made it run smoother but of course slower! Putting my foot down again resulted in more missing, once the hill was climbed then of it went no problems running smoothly at speeds up to 60 mph, but after slowing down to turn into the street which has a slight uphill gradient it starts missing again, almost sounds as if it has lost power to a couple of cylinders, again once the flat is reach no problem and plenty of power. The car did not get above 85 degrees c (on the gauge) it was not boiling when I stopped the engine. This is now the third time that this has happened, after the last time I cleaned all the plugs, reset and cleaned the points, checked all the HT leads and all seemed to be fine. What I do not understand is why it runs so well for an hour or two before it does this. I have noted that the engine bay does get very hot and that the coil feels very hot to touch, but I am not sure if it is the coil heating up or whether it is just the ambient temperature in the engine bay. Any thoughts or advice gratefully received, this problem is driving me nuts!!  | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 187 Registered: 4-2015 |
Mark... I would pursue one of Christopher Carnley's "possibles" as your recent symptoms point in that direction...fuel supply, such as plugged filters, pipes, and notably that sediment filter just past the fuel tank, and before the fuel pumps, usually accessible thru opening in the boot floor, and if not, then from beneath. Most owners are not even aware they exist, although shown in owner manual. 60 years of "non maintenance" is a surefire cause of fuel starvation. They have metal filter discs that get clogged with dirt, rust scale, debris drawn from the tank. There are also small inlet screen filters in the carbs, also typically overlooked although much less likely to be plugged as is the rear tank filter, but worthy of checking and eliminating. I'm just saying. | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 86 Registered: 4-2007 |
Thank you christian The old filter near the tank was removed many years ago and a modern filter fitted, but I did not realise there was another filter in the carb, will check that , many thanks | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 188 Registered: 4-2015 |
Mark... Be that as it may, your described symptoms are EXACTLY those of fuel starvation. The amount necessary for running the engine is, of course, least at idle, slow speed or level driving, and descending a hill, and the most when ascending, or under load, or trying to maintain a high speed, or combinations thereof. The amount being supplied, either due to a restriction (do you have any rubber sections of fuel lines that have been replaced and may be deteriorating from within?) or perhaps a faulty pump, or for whatever reason yet to be determined, is just barely enough to maintain opeartion under "normal or less" requirements, but when you exceed those requirements, the loss of power and popping is essentially the same as running out of gas. When you slow down, crest the grade, or otherwise reduce the load, the "less than ideal" amount of gas being supplied again becomes "sufficient" and operation goes back to normal. Been there, done that. | ||
| Mark Aldridge Grand Master Username: mark_aldridge Post Number: 305 Registered: 10-2008 |
Mark try disconnecting one of the supplies to a carb, pipe the fuel into a container , switch on the ignition and measure the quantity delivered in a specific time. Compare this to the pump spec.If you have a pressure gauge, connect the pipe to this, and check the pump max delivery pressure. If this is OK, fault is a blockage in the carb ? Could vapour lock be an issue, particularly in a hot engine bay ? I have had this on a modified BMC1100 . Mark | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 87 Registered: 4-2007 |
Thank you for the advise, Will check the fuel system, The SU pumps were removed many years ago, thew car now has a single electric aftermarkewt pump, maybe this is on the way out. I will also check the fuel lines | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 77 Registered: 1-2014 |
Coil or condensor, classic symptoms. Failure more pronounced when hot and worse the more load is put on the engine such as going up a hill. You said in the first post you swapped out the coil. Did you replace it with a new one with the correct specifications? Not unknown for a new coil to be faulty either, especially if you put in a cheap one that was made in China. Did you put in a new condensor? No mention of that, it is the second thing I would replace after the coil if a car came in with those symptoms. Not unknown for them to fail soon after installation either. Put new spark plugs in it unless you have platinum or iridium plugs in it. If any sooting is evident on your plugs that will cause missing under increased throttle opening and load. If you can't test the plugs on a plug testing machine that puts a spark to them under compression as they would be when operating in the engine replace them with iridiums, don't clean them. Poor fuel delivery usual symptom is bogging under load and higher throttle opening. Popping, spluttering and backfiring is usually ignition, specifically coil or condensor. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 88 Registered: 4-2007 |
I have checked the fuel pump; it is delivering 85 litres /hour. From what I can find out the original SU pumps were rated to 136 litres / hour, so the fuel is not being delivered fast enough. My pump is just above the delivery rate if only one SU was operating. Has anyone driven one of these cars with only one pump in use, if so did the car run ok at high speed or was it starved of fuel? I blew the fuel lines through with compreesed air, all seemed to be ok. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 78 Registered: 1-2014 |
Mark, you mentioned the distributor cap you're using doesn't have a "fuse" in it to connect to the rotor. This is a carbon brush to transfer the spark to the rotor. If there isn't a carbon brush then there has to be a spring contact arm attached to the rotor to do this. If your rotor doesn't have a spring arm that contacts the distributor cap then the spark jumping that gap will damage the coil. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 79 Registered: 1-2014 |
It'll run just fine with one pump if you're getting 85 litres per hour fuel delivery. That would equate to fuel consumption of about 3 MPG if the engine actually consumed that amount in an hour. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 89 Registered: 4-2007 |
Hi Jim The rotor has a spring contact arm | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 190 Registered: 4-2015 |
Hmmm...interesting. Don't overlook that there may be multiple problems at play...sorry to say that. As to the fuel issue, it either is a fuel starvation problem, or it isn't. Your flow rate is certainly sufficient, but that alone does not eliminate fuel delivery as an issue. Mark A. suggested vapor lock, which would serve to restrict fuel delivery irrepective of the potential flow rate provided by the pumps. How you test for, or simulate vapor lock, I cannot say as I have had no such issues with any of my machines. Thank you, Lord! It remains, however, something to consider until it has been eliminated from the "possibles" list, and also ties in with the "once it cools down, the engine runs fine for a while" symptom. Perhaps try in the "cool of night" rather than "heat of day"? On the other hand, the symptom of the problem going away once you crest a hill, does not seem to correlate with what I would think of as heat related vapor lock, where cooling seems to affect the problem, rather than load on engine, but again, I have no experience to draw upon regarding that issue. Good luck! | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 90 Registered: 4-2007 |
I have ordered a larger capacity fuel pump and I will get the muffler box checked next week. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 80 Registered: 1-2014 |
Coil, condensor. Coil, condensor. Coil, condensor. Nothing wrong with your fuel pump if you're getting 85 LPH. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 91 Registered: 4-2007 |
Hi Jim I am going to replace the coil and condensor for good measure, both are an unknown age and could well be a part or all of the problem. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 1254 Registered: 5-2012 |
Hi Mark I had an identical problem to yours with my 74 Silver Shadow. Because the coil was so new I had ruled it out completely and went on a merry go round of all other possibilities. At that time Jim suggested I replace the condenser and also wrote : "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." On this, I finally replaced my new coil with a new coil and the fault was cured. I had just previously replaced the condenser and this had made a big difference, but the new coil finally put paid to my problems. Of course, during the merry go round I had re-tuned the carbs and changed the ignition timing which I had to correct, once the underlying fault had been cured. This is just my tuppence worth. Your fault may be fuel related but I am glad to see you are going to replace your coil and condensor. The thread I refer to is here: http://au.rrforums.net/forum/messages/17001/17450.html?1430253011 What is interesting is seeing how sure I was the fault was not an ignition problem. Understandable I suppose, as the faulty coil was so new - just a couple of thousand miles on it. I think the other factor was with a fault like this, it intuitively feels like fuel starvation, but most often it isn't. Geoff | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 92 Registered: 4-2007 |
Another update to this saga! I have replaced the coil, condenser and the points. No change to the status, runs perfectly for about 40 minutes, even up the steepest hills then it starts coughing , missing and popping, in fact if anything it has got worse, barely got up the driveway, had to resort to 1st gear and it only just made it. And when I did switch off there was a very loud back fire from the exhaust. I have ordered a new pump and will fit it next week. The rattle from the exhaust is getting worse, so I will get that checked next week. In the meantime work on the car stops as I have to go to work for a few days. Thank you to everyone for their advice - I will get there in the end, it is just so frustrating | ||
| Mark Herbstreit Prolific User Username: mark_herbstreit Post Number: 148 Registered: 5-2005 |
Could the exhaust rattle be the clue? A loose baffle moving around in the muffler blocking the exhaust intermittently could be a problem. | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 83 Registered: 1-2014 |
The fact that you have disturbed those parts and it is worse is a big clue. The fact that it backfired out the exhaust when you switched it off also points pretty definitely to an ignition problem. Don't assume those parts you installed were good. Condensors have a finite life span and if it has been sitting on a shelf for years it could be faulty even though you just bought it. Also cheap condensors made in China are suspect. Are you sure the condensor is connected properly to the points and that the points are set correctly? I think you will find the problem is with the points and condensor, either faulty or not connected properly or adjusted incorrectly. SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| richard george yeaman Grand Master Username: richyrich Post Number: 508 Registered: 4-2012 |
Most definitely an ignition problem trust the professional advice. Richard. | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 198 Registered: 4-2015 |
Jim... Your assessment of condensers is just too depressing for words! If the current state of aftermarket replacement parts is such that they are now like yogurt...with a limited shelf life...we are all going to have to get one of those "handy-dandy coil and condenser test units". In your position in the industry I can see how they would get used constantly, especially if in today's world "straight out of the box" means nothing. If one had one in their inventory of tools, checking coil and condenser every time oil is changed would become "de rigeur" in order to keep tabs on the status of ignition components on the thoery that it is easier to do at home, than on the side of the road. What would you say the expected shelf life is? Is it variable based on the quality of manufacture, or is it something about the interior materials that simply goes bad over time irrespective of manufacturer? | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 93 Registered: 4-2007 |
Jim I think you are right The distributor was remodelled some time ago to single points, I think I need to take this to a good auto tune or Elec to get the ignition system thoroughly checked, I am not convinced the dwell angle is correct and the engine just does not sound “right “when it is timed with a strobe it sounds like it is too far retarded. I think it will be some time before I can get back to the car, work and a trip overseas coming up. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 1256 Registered: 5-2012 |
Mark If you are not too fussed about originality then another option would be to fit electronic ignition. I know that Hubert Kelly has been successful in converting his twin point distributor using a Powerspark unit. They will work on a Mk6. http://www.simonbbc.com/rolls-royce-bentley Geoff | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 94 Registered: 4-2007 |
Geoff Electronic ignition sounds like a good option ,I am going to look into this and check with the auto electrician. No need to worry about originality, i am more interested in reliability! | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1545 Registered: 6-2006 |
Hi Mark, have you replaced the rotor to? There are some that do exactly as you describe. Weird and I'm not sure why. I think I read somewhere that the plastic had a carbon content or too high a carbon contact. Distributor doctor or somewhere similar perhaps? Are you timing it on the flywheel? | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 95 Registered: 4-2007 |
hi Paul I have not replaced the rotor, most probably a good idea to do so, I also noticed one plug lead has a small cut in the insulation so I will be replacing all the leads. I am timing it on the fly wheel, but somehow the engine just does not sound quite right when I time it this way, thinking of just static timimg it using the trusty light bulb method when at TDC | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 220 Registered: 7-2007 |
Hi mark, I may have mised it, but have you replaced the plugs? I see you cleaned them twice. My opinion for what its worth is you cannot clean plugs running on unleaded fuel, for 3 bucks each replace them. I change out my plugs once a year, iridiums to my mind are not worth it for these motors. Cheers Marty | ||
| Peter McCarthy Unregistered guest Posted From: 61.69.100.46 |
Mark, my special has been fitted with an electronic ignition unit from an early 90s (could be 80s)Commodore. I had it checked and the centrifugal advance curve matches exactly the original Bentley spec. A very cheap option, though an extension under the distributor needs to be made up. Let me know if you want to know more. Regards Peter (Message approved by david_gore) | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 96 Registered: 4-2007 |
An update. I cannot be 100%v sure what was causing the problem, I suspect a multitude of things, but the car is now running better than ever. I have done the following Renewed the electric pump, with a genuine FACET pump, the other pump was a Chinese copy. Changed the fuel filter. Reset the carbs and adjusted the mixture, noted a vacuum leak on the manifold which is temporarily repaired until new gaskets arrive. Renewed, coil, plugs, points and condenser, retimed the engine, seems the markings on the fly wheel are not correct so did this by ear / and static timing. Great to have the car running well again Many thanks for all the input and ideas. | ||
| Carl Heydon Frequent User Username: car Post Number: 95 Registered: 2-2004 |
Great to hear, Mark. Isn't it a wonderful feeling when it all comes together. I have been struggling with poor performance in B229FU as well and finally resolved it yesterday (my stupidity). The post below, re pistons, is about the ones you gave me. I think your father dismantled the engine. Are you able to furnish any info? |
