| Author | Message | ||
     Marty Unregistered guest Posted From: c211-30-202-33.carlnfd3.nsw.optusnet.com.au |
Hi guys & girls, Have a problem with my MK VI fouling plugs for the first 10 minutes of starting from cold. As the old plugs had seen a few miles, I changed them, going from NGK bp5s to bp5es as the extended point is supposed to run cleaner. For the first two cold starts everything was fine, started it yesterday, back to the old problem. I am running on Caltex Vortex PULP 95 octane, without any additives, and open the manual choke all the way up to start, and close it as quickly as possible to avoid over fuelling. Any thoughts?? Cheers Marty (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 673 Registered: 4-2003 |
Hi Marty, Quick questions that might help our information providors: Is the fouling black or orange? If it is black; is it an oily deposit or dry? | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1139 Registered: 4-2003 |
You say plugs, not just one plug, Marty. As David suggests, check the type of fouling. However, for all six to foul so incredibly quickly, I would go straight to the carburettor float bowls, looking for a bad float or a leaky needle causing extreme flooding. Those NGK BPRx or BRx are very tolerant to poor combustion, so something simple has hung up. If one plug fouls only (oil), it is of greater concern than if all foul (fuel). If the fouling is evenly evident on all six plugs with twin carburettots, I would also look for a blocked or non-standard air cleaner, or a seriously malfunctioning choke system. The fuel you use is fine, and you are quite correct to avoid all additives in my opinion. RT. | ||
| Marty Unregistered guest Posted From: c211-30-202-33.carlnfd3.nsw.optusnet.com.au |
Hi David, When I pull the plugs they are black. Looks dry to me. The car uses no oil, blows no smoke. When I first start it up and drive out of the garage, it is fine, I leave it to warm up at a moderately fast idle while I close doors, gates, etc, and then, after say, 2 minutes of idling, it starts running on 5. Takes 10 minutes of driving to clear itself. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 674 Registered: 4-2003 |
Marty, First test - after you get the car out of the garage and let it idle before starting out; as soon as the engine starts its "lumpy idle"/run on five cylinders routine - remove the air cleaner/filter and see if the idle speed increases. If so, there is a restriction in the intake system before the carburettors with the most likely candidate being a clogged air filter element. If the idle speed is unchanged then the problem is most likely either in the carburettors as Richard suggests or possibly in the distributor cap/rotor or high tension leads dedicated to the cylinder which fouls the plug. please let us know what you find. | ||
| Marty Unregistered guest Posted From: c220-239-253-159.carlnfd3.nsw.optusnet.com.au |
Hi guys, Went over everything, didn't find anything out of place. Started it up, it ran perfectly! Did a run last night in the cool air from Rydalmere up to Newport, then back down across the bridge to the city, and home again up Victoria Road. Is it just me, or do they seem to run smoother in the cool night air? I was enjoying the drive so much, I forgot I had a bride and groom in the back, or maybe it was when I couldn't see them in the rear view mirror? :-)) (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 678 Registered: 4-2003 |
Hi Marty, The power output of an engine is proportionaly related to the mass of the fuel/air [not volume] mixture drawn into each cylinder. At night time, the air is cooler and has a higher density meaning it has greater mass and this is why you have [not seem to have] more power. This is also why your engine has less power on hot days and at higher altitudes. Given your observation that your car ran better and did not "play-up", this suggests to me that your carburettor needle setting might be too rich and it may be worthwhile having these reset before doing anything else. | ||
| Martin Cutler New User Username: martin_cutler Post Number: 6 Registered: 7-2007 |
Hi David and all, Gosh time flies. 10 months since I had this problem. I put a new set of plugs in, went for B5ES instead of BP5ES as I had in previously. Went fine for the first few outings, now back to it's old self. I had the mixtures checked, they where OK. I took off the old metal weave type of air cleaner, and replaced it with a paper element. It doesn't do it every time, which is the most frustrating thing. I purchased a set of BP5ES to put in, which I will do next weekend. I am not sure if this will make the difference, but will try anyway. last time it did it, I took the plugs out to clean them, #1 was wet. I expected #6 to be the problem, as I would have thought there would be more bore wear at the rear, therefore more oil consumption. Had a nice run to Camden yesterday. I have now swapped to 98 octane petrol, as my local Caltex has dropped the 95 in favour of E10, which I don't think I want to try in the Bentley. Would the ethanol blend burn hotter or colder? Will keep you posted on the fouling issue. Cheers Marty | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 170 Registered: 7-2007 |
Hi guys, B256MD has behaved herself for 4 years! Have covered around 4000 miles in that time. Has been behaving well, but I foolishly put a new set of plugs in her, and the old problem reappeared. Took her down to Jamberoo, played up only under load, but came good when I drove back up Mt Ousley, ran magnificently in top gear all the way, sitting on 50mph. Came home, checked the new plugs, checked leads and cap, changed the plugs again, ran fine last weekend. This weekend, played up again! Just cleaned and reset the points gaps, went around the block, didn't falter at all under load. Starts fine hot and cold, idles fine. Very strange....... P.S. Head is off the R Type! Cheers Marty | ||
| Chris Gillings Frequent User Username: chrisg Post Number: 72 Registered: 4-2001 |
What you describe is remarkably close to my current experience with B290MD. The brand new exhaust manifolds and mufflers are working fine after a false start with reconditioned manifolds. (Hint: NEVER buy re-welded manifolds! But that's another story.) I find that if I take all the plugs out and clean them she runs fine but only as long as I let her get nice and hot before switching off. In desperation I went for hotter B6ES plugs but I doubt that it's made much difference. I also get that ever so slight missing under load. Would I be better off with BP5ES plugs? As all the plugs are dry but seriously coated in carbon I can convince myself that it's not oil fouling but that she's running very very rich. My problem, though, is that I have yet to meet anyone who seems to really know how to tune these cars properly. It's probably high time I learnt to tune her myself. I've read various manuals on SU tuning but I just don't seem to have 'the ear'. As I learn best by watching and then doing would anyone be interested in teaching me? I've also discovered that plug cleaners are no longer available retail. Everyone I ask says "just buy a new set". Well, I've got four now so I can't see the point. | ||
| Carl Heydon Experienced User Username: car Post Number: 22 Registered: 2-2004 |
Hi Chris, Old style plug cleaners blasted the insulator with abrasive and very effectively removed the glaze from the ceramic allowing them to foul so much faster next time. Spray them with Carbi Cleaner and blow of with air and they will be fine. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2424 Registered: 4-2003 |
Chris, Yep. Chris, I have been having this issue temporarily as my R-Type B174UM has been sitting around idling (pardon the pun), but it is solvable in a jiffy. The SUs are not difficult to tune by the way. The plug fouling syndrome is usually only apparent when the vehicles only do short trips. Go for a protruded plug as you suggest if that is the case. For short trips, the BP5ES is ideal. I put some BPR5ES plugs in with instant success, but will swap them back to 7s once the cars has done a trip to Sydney and back to Canberra. A couple of notes. This type of plug fouling is often caused by a poor air cleaner as well as low speeds and minimal loading. Whatever the cause, I have found that it takes maybe 100km of continuous loaded use to clear. Until the soot in the combustion chambers has all cleared out plugs can peg or foul in no time. RT. | ||
| Stefan Morley Grand Master Username: myupctoys Post Number: 328 Registered: 7-2009 |
Richard, Certainly the hotter plugs make a difference. This is probably totally left field but thought I'd contribute. Rebuilding a Supra Engine at the moment, taking up space in the garage hence the long finger with the Bentley. It blew a head gasket (combustion gases in the coolant, fortunately not the other way) but what is interesting as part of the rebuild of the top end, there was a lot of oil in the inlet manifold. The oil has not come from the crankcase breather but actually been drawn in from the crankcase via the valve stems and past the valve stem seals. The breather on this car is actually between the air filter and the throttle so oil won't be sucked in here under idle, aka has to be somewhere else. Surprised how worn the seals are given its only done 100k. Thought process, if the car is only driven lightly the manifold depression is always under vacuum (idle is 23 inches hg) and trying to suck air where ever it can. If the seals are worn only going to suck air from the crankcase past the seals. I know its a totally different car but after seeing your in-situ seal replacement (yeah still impressed with that) was wondering if the same might hold. Stefan | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2425 Registered: 4-2003 |
Here is a new B6ES after a run of 10km. Note that it has fouled a bit. B6ES is a good allrounder once the motor has been given a good run to clear it all out. I'll run the BPR5ES (good, but old, plugs from the T-Series) for a while then pop the B6ES plugs back in. B7ES are fine for a car that is used regularly, but 6s do no harm and are fine if you only do 3,000 miles or so each year and mainly in city traffic. .  | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2426 Registered: 4-2003 |
Stefan, good point about the valve stem seals. Not only are they necessary on the V8s, but also on the 6s. On B174UM, I fitted PTFE positive valve stem seals from Crane Cams about 30 years ago and never looked back. I still have the special machining tool to dress the valve guides. Cranes went out of business last year, but there are others, and some don't even require any machining, such as the kits (viton seals and spacers to replace the old seal caps) sold by Introcar for in-situ fitting. Viton seals are probably the optimum, but all positive seals make the ropey waxy valve stem seals on Crewe cars until 1983 look downright silly. It changed the R-Type from burning at least 4 litres every 1,000 miles to absolutely nothing. Between oil changes the oil level does not budge anymore and it stays clean. It certainly did the plugs no harm either ! Among others, I did the same to a friend's Silver Dawn in Geneva, and a gentleman in Melbourne fitted the same Crane seals to his early Silver Dawn a few years back and was also very impressed. The same applies to a certain concours' Phantom III I know with the Viton seals. All the reports on the Viton and PTFE seals are equally impressive. On Chris' note on welded manifolds, I do concur despite the ridicule I have suffered. I have a few cracked R-Type manifolds in the shed, two having been welded only to fail weeks later, as proof. All the heat treatment and special techniques failed. RT. | ||
| Stefan Morley Grand Master Username: myupctoys Post Number: 329 Registered: 7-2009 |
Richard, Didn't realize Crane has disappeared. Been a big name for many years. The Supra is an extreme case but guess there are always degrees. Over the years think there has been significant improvements in material science behind designs of engines and how well materials work together with expansion co-efficients. New cars function almost as well from cold to hot but older cars change as they heat up. Certainly notable with Valves, Valve Stems and Guides but not limited to that. Don't just hold the valve in place but perform a very important function of getting rid of heat into the block. Having impact on sealing and wear rates. Older cars the different metals expand at different rates and short trips do them no favors. Not that the older cars are bad just that over the years there has been greater understanding. My first car was a Kombi, always fouled plugs on short trips, Adelaide to Sydney never an issue. Loved that car, the good and the bad. Description of Mt Ousley brings back memories in the Kombi.... Certainly wasn't top gear. Cheers Stefan (Message edited by myupctoys on 10 October 2011) | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 805 Registered: 6-2006 |
Marty - hoping not to cause offence but - have you gapped the plugs? They come out of the box with a much larger gap these days (too big for old type coils). Just a thought. | ||
| Chris Gillings Frequent User Username: chrisg Post Number: 74 Registered: 4-2001 |
Those gaps should be 0.025", right? I'll be putting in six brand new BP5ES plugs tonight. I also got six BP6RES as well, just in case. | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 171 Registered: 7-2007 |
Hi Paul, Yes, I gapped the plugs. They are around 30 thou out of the box, brought them down to 25 thou. Hi Richard, On your advice I took the Corolla paper air filter out of B256MD about 2 years ago, and refitted the original oiled wire mesh, didn't make any noticable difference at the time. One thought I had was that the points gap might be effecting the size of the spark. 20 thou gap would give a shorter dwell than, say, 15 thou, ie, shorter dwell, less time for the coil to build up a spark, smaller spark. What do you think? Should I set the points gap smaller and see if that changes the situation? Hi Chris, re exhausts, I brazed up a manifold for a guy with a Daimler Regency, lasted a month. He got a guy in Penrith to make up new manifolds in steel, haven't seen them yet, but will be fitting them for him in a week or two. Cheers Marty | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2428 Registered: 4-2003 |
A question for you all, assuming that you have not downgraded to negative chassis which accelerates carbodybody corrosion by an order of magnitude (consumable anodes etc): What ignition coil are you using, and which side (+ve or -ve) is connected to the points ? Using an original +ve chassis coil, the coil's +ve terminal should be to the points, and the -ve terminal to the battery side. If using an aftermarket coil made for a +ve chassis car, then the -ve coil terminal should go to the points and the +ve to the ignition circuit (i.e. +ve of the coil should be connected to the -ve of the battery). Simplistically this sounds incorrect. Most autoelelctricians, parts suppliers and mechanics make the wrong assumptions and fit them back-to-front, but it is true from an engineering perspective. Coils are autotransformers. Connecting the coil the wrong way will burn the points, stress the coil, and foul the plugs. RT. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2429 Registered: 4-2003 |
To warm your heart, Here is the Dymo tape I put on the underbonnet in 1972 before I even had a drivers' licence to remind me. I just ducked sownstairs and took a pic on B174UM. Gosh, Dymo ! Remember that ? 300,000 miles later it has served me very well. Spot the location. LHS underbonnet near the rear hinge. Message: if all is well, the gaps shown on the Dymo are just dandy. RT.  | ||
| Chris Gillings Frequent User Username: chrisg Post Number: 76 Registered: 4-2001 |
My coils and condensers appear to be original (or at least old enough to vote). I've not touched them since buying the car in 1994 and I doubt if anyone else has. I'm setting plugs to 0.025" - BP5 and BP6 alike. Speaking of dwell, I checked the static timing tonight (though not the point gaps - must do that) and then found myself wondering what should the dwell actually be? The workshop manual (TSD 2292) advice on tuning is a bit offhand, to my mind. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2431 Registered: 4-2003 |
A note on tuning the way I do it. Everyone has an individual way, but this works for me. I have a figure for dwell that I shall not quote as I am never convinced that dwell is the last word with dual points where the setting of each pair of points interact with the dwell. As the points gap is 1:1 with the dwell statically, I simply set both sets of points to .020” as there is no external dynamic adjustment for the points once the distributor cap is in place. By contrast, the T-Series has an external dwell (gap) knob which is great as you can adjust the points gap/dwell with the motor running (i.e. dynamically). The first step is to synchronise the points. The book shows how to do it statically, giving a very poor degree of accuracy which leaves some motors far from smooth. By contrast, I use two strobes, one on pot 1 and the other on pot 6, to set the points synchronisation. With a white marker pen, put a stripe on the front crankshaft pulley as a reference for the strobes. The white mark has no meaning in absolute terms as the vibration damper/slipper drive is in there, but to synchronise the points it is the way to go. It’s a bit of an iterative operation stopping and starting the motor to open the distributor and swing the adjustable points into position, but once the two strobes align then the points are synchronised dynamically, something the manuals never foresaw. That way I can be fairly certain that they are correct. Then the spark advance. It may sound a bit guessey, but so is fuel quality. The ideal absolute figure for the timing varies for several reasons, and the static measurement stated by Crewe 60 years ago may be as much as 15 degrees from ideal. With the motor warmed up, advance the spark in stages on a few test runs, until the motor just starts to pink/ping on full throttle at low engine speed, say 1200rpm (try 25-30 mph in top gear on full throttle). Then hook up the strobe and back off the spark by 3 degrees. That’s it. There is no need ever to climb around to find the flywheel timing marks, which on the R-Type automatics are even worse than on a MkVI as they are at the lowest point underneath and very inconvenient. RT. | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 172 Registered: 7-2007 |
Hi Richard, Thanks for the info on the coil. On B256MD, which is +ve earth, I had the +ve terminal of the coil going to the points. I have just changed it to the negative terminal on the coil going to the points. I will let you know if this solves the problem. On B319LH, which has been converted to -ve earth, (A/C, CD player, GPS, etc), the -ve terminal of the coil is to the points. Both coils are modern Bosch coils. Very interesting, thanks for your input Richard. I also just ordered a set of valve stem seals from introcar, will let you know when they arrive. Cheers Martin. | ||
| Mark Taxis Frequent User Username: mark_taxis Post Number: 60 Registered: 4-2007 |
Hi Richard Your comments re the timing marks are very interesting. When I installed the 4 1/2 l engine in my Mk 6 special I timed the car "by ear" as the strobe was not working. The car ran well. When I eventually bought a new strobe I checked the timing and found it was way out according to the the marks, I adjusted the timing to TDC, but somehow the engine did not sound right, it was almost like the engine was labouring on idle. Also there was a tendancy to backfire on the overrun. Since then I have advanced the timing about 10 degrees and the engine now runs a lot sweeter and the backfiring has stopped. I must admit that dwell etc is beyond my technical know how. The distributer in the car has been converted to a single point system this was done during a full overhaul of the unit - maybe this is the reason for the timing marks being incorrect? Regards Mark |
