Spark plug fouling
Discussion
I have a 1985 Bitter SC which I bought in 1993, I am the second owner and the car has now done 56,000 miles, the engine is based on a 3 litre Opel Senator but has been bored out to 3.9 litre by Erich Bitter who made these cars, the car is petrol fuel injected. Unfortunately on short runs, often stuck in traffic queues, the plugs are fouling (carbon fouling?), this is very fine needle like "whiskering" between the plug electrodes and this occurs in less than 30 miles. I have changed the plugs (NGK BPR6HS), plugs leads, coil and distributor cap and had the timing checked all to no avail. I have changed the plugs to a hotter BPR5HS and after speaking to an ex sidecar world championship passenger who used to work for NGK reduced the spark plug gap from 28 thou to 24 thou. I use fuel injector cleaner at every fill up and the car is not smoking or using oil (apart from the odd oil leak) and this is now driving me mad. If anyone one has a suggestion that would cure the problem I would be eternally grateful, perhaps a dose of Redex down the plug holes to clear out any carbon build up?
Does this help? http://www.senatorman.de/ljetronic.htm
It's in German, but if you're on Google, a "translate this page" button should appear.
JOhn
It's in German, but if you're on Google, a "translate this page" button should appear.
JOhn
Mave said:
Fuelling is where I'd look as well. Also, has it just started doing it? Any problems with running temperature?
I do not use the car that much but yes it must have been occurring within the last 1,000 miles, it was fine before then and just suddenly starting happening. I have tried different fuels such as Shell VP which I like in my old classic bikes as it makes then run much better. It seems to occur mainly on cylinder 2 (from the front) which is the worst and cylinders 5 & 6 much less often, so maybe it is something to do with the injectors themselves? Thanks.tapkaJohnD said:
Does this help? http://www.senatorman.de/ljetronic.htm
It's in German, but if you're on Google, a "translate this page" button should appear.
JOhn
Thanks for this John but I could not see any translate button. But then having been caught by a speed camera recently in Austria on my Norton Commando and trying to decipher the paperwork written in German and emailed to me and then pay the fine on line was a nightmare, it would have been easier for me to take the 1 day and 13 hours in jail offered to me!It's in German, but if you're on Google, a "translate this page" button should appear.
JOhn
First and foremost, you need to know what sort of mixtures you are running, both at idle and this normal driving.
That will give you an indication as to where to look to try and fix whatever the problem may be.
But also some sort of ignition test to verify there is a good strong spark available.
That will give you an indication as to where to look to try and fix whatever the problem may be.
But also some sort of ignition test to verify there is a good strong spark available.
Kenny Biker said:
I do not use the car that much but yes it must have been occurring within the last 1,000 miles, it was fine before then and just suddenly starting happening.
So why are you messing about with plug grades and plug gaps which have always been fine in the past when they can't possibly be the cause?Hi Mignon,
I am doing this as it has been suggested by "experts", e.g. the chap who used to work for NGK and has written a book on spark plugs. It is also a question of trial and error and eliminating various possible causes. This may have began when I started picking up the grandkids once a week and getting stuck in the terrible traffic jams that we now continually get in Croydon Surrey. I am surprised that out of the many "experts" that I have asked someone cannot point to the probable cause of the problem but some have suggested that the likely cause is fuel and I am very grateful for all the people who have tried to help, so many thanks. The Bitter at the time was my only/everyday car and whilst I like it the 15 mpg is a bit of a blow, maybe the heavy fuel consumption is a clue but it is used mainly around town and I have been told that the average fuel consumption for a 3.9 litre Bitter SC averages only about 18 mpg anyway. Another chap that I spoke to who is involved in car electrics thought that it was an electrical problem as he had the same problem when he was involved in racing MGB's in America and it was electrical though he could not remember exactly what the problem was.
I am doing this as it has been suggested by "experts", e.g. the chap who used to work for NGK and has written a book on spark plugs. It is also a question of trial and error and eliminating various possible causes. This may have began when I started picking up the grandkids once a week and getting stuck in the terrible traffic jams that we now continually get in Croydon Surrey. I am surprised that out of the many "experts" that I have asked someone cannot point to the probable cause of the problem but some have suggested that the likely cause is fuel and I am very grateful for all the people who have tried to help, so many thanks. The Bitter at the time was my only/everyday car and whilst I like it the 15 mpg is a bit of a blow, maybe the heavy fuel consumption is a clue but it is used mainly around town and I have been told that the average fuel consumption for a 3.9 litre Bitter SC averages only about 18 mpg anyway. Another chap that I spoke to who is involved in car electrics thought that it was an electrical problem as he had the same problem when he was involved in racing MGB's in America and it was electrical though he could not remember exactly what the problem was.
Hi again, I am not sure how you check the strength of the spark but I do get a good spark with the plug outside the engine when the engine is turned over, I also checked the spark with a spark tester whereby you increase the gap in the tester and I got quite a big gap before the plug did not spark.
finlo said:
Didn't Jetronic system have an additional injector for cold start enrichment?
If so could this be somehow remaining active?
I did wonder if it was something to do with the weather getting colder - either cold start enrichment, or if it's got a water jacketed inlet manifold then a thermostat problem could lead to long extended running with a cold manifold.If so could this be somehow remaining active?
Answers, I hope, to some questions:-
a) I do not know about the emissions when "driving", I have not got any written results.
b) Any adjustment to the idling mixture was done by the mechanic but I think that there was very little if any change.
c) The Jetronic injection system is apparently the "L" and not "LE" and I do not know anything about an enrichment injector. The manifold does not have a water jacket inlet manifold. I have been told that the Jetronic L injector system has separate resistors, I am not an experienced mechanic. I am leaning towards trying new injectors on cylinders 1 & 2, I have been told that I need Intermotor fuel injectors 14558, are these easy to replace or should I get a garage to do this? Many thanks.
a) I do not know about the emissions when "driving", I have not got any written results.
b) Any adjustment to the idling mixture was done by the mechanic but I think that there was very little if any change.
c) The Jetronic injection system is apparently the "L" and not "LE" and I do not know anything about an enrichment injector. The manifold does not have a water jacket inlet manifold. I have been told that the Jetronic L injector system has separate resistors, I am not an experienced mechanic. I am leaning towards trying new injectors on cylinders 1 & 2, I have been told that I need Intermotor fuel injectors 14558, are these easy to replace or should I get a garage to do this? Many thanks.
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