Author Topic: Intermittent bad misfire (Read 23950 times)

DavidBrough · « **Reply #25 on:** June 20, 2011, 11:31:06 »

Hi Jay,

If the new plugs you obtained from Mercedes are not NGK BP6ES then you should change them, I had misfire problems some time ago which turned out to be plug related and the only reliable fix for me was to use NGK. I found the worst culprits to be Bosch and Champion plugs which broke down very easily and quickly in my engine. I think most people here would recommend NGK.

jaymanek · « **Reply #26 on:** June 20, 2011, 12:19:02 »

I will try them but I cant the the relationship with heat?

The car runs super strong until.... well until it doesnt!

I have ordered some NGK BP6ES but got to be a long shot.

I am now wondering if there may be a relationship/issue with the WRD?

ja17 · « **Reply #27 on:** June 20, 2011, 13:03:52 »

Hello Jay,

How about sediment in the fuel tank? Top off the fuel and see if it helps. If the entrance to the flower pot, in the tank, becomes clogged with sediment, the engine will starve for fuel after a short time. If let to rest, it will start and run again for a while. Topping the fuel level allows the fuel to run over the top rim of the "flower pot" and will allow the engine to run without fuel starvation.

Not much chance that the WRD is the culprit. Check it by seeing if its air intake is open during cold running and closes after warm up.

jaymanek · « **Reply #28 on:** June 20, 2011, 13:10:00 »

Thanks,

The problem occurs even with a full tank... Its definately related to temperature somwhere... whether thats coolant temp or just heat build up, im not sure.

Raymond · « **Reply #29 on:** June 20, 2011, 21:12:38 »

Sorry if I missed it, but how old are the plug and distributor wires? I once had a '63 Chevy that only misfired when hot. I looked under the hood in the dark on night and could see two of the plug wires arcing to the block.

IXLR8 · « **Reply #30 on:** June 20, 2011, 23:12:34 »

Probably way off the wall, but is the battery OK and well connected with clean, tight fittings?

May be OK, as is, at lower temperautures, but with heat, may be not well connected. Just a thought.

Joe

UKSteve · « **Reply #31 on:** June 21, 2011, 08:06:18 »

Hi, something to consider:
Although on very different cars, I have experienced identical symptoms.
An old Ford Sierra and a BMW 2000. The issue in both cases was thought to be ignition but turned out to be condensation in the fuel tank working its way up to the carburator.
When I took the carb apart, I could clearly see water droplets in the float chamber on both of those cars.
I've read quite a bit about fuel tank issues on this forum.
It might be worth checking your fuel filter. Try and remove it without spilling out the fuel. That will give you an opportunity to identify any water droplets.
It wont cost anything, and at the least will eliminate one potential cause.
Cheers
Steve

jaymanek · « **Reply #32 on:** June 21, 2011, 08:27:29 »

Hi All,

The leads are new but I will take a look under the bonnet at night... although its a little difficult at the moment as it doesnt get dark until very very late!

Fuel tank issues did cross my mind... I changed the fuel filter a couple of months ago when I carried out a full service. The fuel filter did have more debris in it than id expect but I know the fuel tank was cleaned just before I purchased the car early last year and so i assumed that this is just left over stuff.

However I just think these sorts of issues would show up consistently at all temps... I dont see the relationship between the car warming up and a potentially clogged or contaminated fuel system?

My car is currently at the bodyshop having the dash repainted (been putting that one off for a long time!) but when its back ill need to spend some time under the bonnet.. it must be something ive disturbed or changed when I did the head rebuild....

ja17 · « **Reply #33 on:** June 21, 2011, 14:06:44 »

Hello,

I would not rule out fuel yet. If the filter had debris in it, your system still could be clogged. The relationship may not be the engine temperature, but the amount of run time before the engine starves for fuel. The screens in the electric fuel pump or tank screen could be clogged.

I would remove the fuel sender in the trunk and have a look in the tank to see if it is still clean.

philmas · « **Reply #34 on:** June 21, 2011, 15:55:21 »

Quote from: DavidBrough on June 20, 2011, 11:31:06

Hi Jay,

If the new plugs you obtained from Mercedes are not NGK BP6ES then you should change them, I had misfire problems some time ago which turned out to be plug related and the only reliable fix for me was to use NGK. I found the worst culprits to be Bosch and Champion plugs which broke down very easily and quickly in my engine. I think most people here would recommend NGK.

I have to agree with that.NGK saved my life! BTW, I had misfiring issues mainly whith warm or hot engine before I changed the plugs.

jaymanek · « **Reply #35 on:** June 26, 2011, 13:34:54 »

NGK Plugs installed, no difference, although the old ones were very sooted up... have now set the co level at idle which was a touch high.

However, opened up the tank and the lining has fallen apart... there were large sections of the lining sat at the bottom of the tank.

Where is the best place in europe to buy a new tank? SLS is my usual supplier who seem to supply them at 400 EUR.

Mercedes are too expensive at £800 GBP + tax.

DavidBrough · « **Reply #36 on:** June 27, 2011, 11:50:54 »

Try Roger Edwards Motors in Amersham 01494 766766.

ja17 · « **Reply #37 on:** June 27, 2011, 12:44:24 »

Hello Jaymanek,

It looks like you are at the root of the problem.

jaymanek · « **Reply #38 on:** June 27, 2011, 13:07:05 »

maybe I hope so...

Ref the tank, Roger Edwards says he uses Dealer parts where possible but he has also used the SLS part. He says the quality is not as good as the original.

I would expect this but I cant justify spending £800 on a hollow metal container so have ordered the SLS unit.

jaymanek · « **Reply #39 on:** July 04, 2011, 10:42:44 »

New tank fitted... Im not convinced it caused my problem...car seems to drive good but the car did give a hint of playing up again once or twice on the drive home - nowhere near as bad though.
Need to go on a longer drive to be sure.

If the problem is still there I think I have to retrace my steps from doing the head rebuild, it just has to be linked as I had no such problems before I did the head gasket.

Would fuel pump timing cause such issues?

jaymanek · « **Reply #40 on:** July 12, 2011, 18:13:50 »

Still having issues but I think I may have cracked it... i hope.

Decided to test the fuel flow and was getting around 1-1.5L per minute. This was at the return at tank.

So decided to remove the fuel pump and take it apart... Well I quickly found that the pump was clogged at its intake, there is a small filter from which i removed so much dirt that I wionder how any fuel got past it at all!
I took the pump apart to clean it out but unfortunately the seals all fell to pieces.
It appears the seals arent available from MB for my short fuel pump?

I put it back together with some other seals I had in an assortment, but the fit isnt perfect and for some reason the pump wont pump any fuel, although the motor is running.
Ill play with it another day again.

I decided to order a new bosch fuel pump... very expensive but I hope it will sort out my problem once and for all.

Benz Dr. · « **Reply #41 on:** July 12, 2011, 22:04:25 »

I would NOT put any sort of lining in a fuel tank. My rad guy told me that the new fuels disolve that stuff and it makes one hell of a mess. Best to leave it bare and keep if filled with fuel.

ja17 · « **Reply #42 on:** July 13, 2011, 04:15:21 »

Hello Jay

When the fuel pressure or volume is low, check the screen in the tank, the screen in the intake of the fuel pump and the main fuel filter.
Fuel pressure and volume tests are used to diagnose these problems. If any of the filters or screens become clogged, the fuel pressure or volume will be low. This test is a little work but can save you from replacing a lot of expensive parts.

jaymanek · « **Reply #43 on:** July 13, 2011, 10:59:56 »

Yes thanks, ive now learnt all about the fuel system! Ive replaced the tank, new bosch pump on my desk to be fitted today and new filters will be fitted.

Really hope thats the end of it.

mdsalemi · « **Reply #44 on:** July 13, 2011, 11:42:58 »

Quote from: Benz Dr. on July 12, 2011, 22:04:25

I would NOT put any sort of lining in a fuel tank. My rad guy told me that the new fuels disolve that stuff and it makes one hell of a mess. Best to leave it bare and keep if filled with fuel.

Yes of course, Dan. But, there are too many people out there that will not come to realize that their fuel tank has reached the end of its useful life, and do not want to spend the money on a replacement. They are expensive, no doubt--and even the repros are not cheap--but what is on this car? But when you have an end of life fuel tank, a replacement is the only permanent solution. I was told that years ago (perhaps to make me feel better about the $1,100 the new one cost at the time) and I don't think anything has changed.

Jaymanek, if you are replacing the fuel pump, ensure you have a new set of mounting studs. Those are not expensive, but if you have not had the pump off before, you may not be able to salvage the old ones. At least one of mine broke; the others were not usable. It's a hard life underneath a car...

jaymanek · « **Reply #45 on:** July 13, 2011, 12:08:04 »

I used a repro tankf rom SLS.. I painted the outside and have wax protected it too...
Didnt touch the inside of course.

Im changing the main bracket, mounts, screws, nuts etc

Benz Dr. · « **Reply #46 on:** July 13, 2011, 17:24:06 »

Quote from: mdsalemi on July 13, 2011, 11:42:58

Yes of course, Dan. But, there are too many people out there that will not come to realize that their fuel tank has reached the end of its useful life, and do not want to spend the money on a replacement. They are expensive, no doubt--and even the repros are not cheap--but what is on this car? But when you have an end of life fuel tank, a replacement is the only permanent solution. I was told that years ago (perhaps to make me feel better about the $1,100 the new one cost at the time) and I don't think anything has changed.

Jaymanek, if you are replacing the fuel pump, ensure you have a new set of mounting studs. Those are not expensive, but if you have not had the pump off before, you may not be able to salvage the old ones. At least one of mine broke; the others were not usable. It's a hard life underneath a car...

I'm aware of that. However, some may be have an otherwise perfectly useable tank after cleaning and go back to nothing by having it coated inside. Having said that, some people may find that some coatings work just fine, sometimes. Which coatings, used with which fuel, and under what conditions, isn't for me to even begin to guess about.

jaymanek · « **Reply #47 on:** July 14, 2011, 09:53:39 »

Massive difference with new fuel pump!

The car starts on the button now, no cranking at all when hot.

I think that had to be the problem, makes sense... Under load the engine was struggling to draw enough fuel.

W113SL · « **Reply #48 on:** July 15, 2011, 12:34:34 »

I'm with Joe. Check the color of your plugs. An overly lean mixture will not show itself until all elements of the cold start system have been minimized i.e. the engine is at full operating temp. Good luck, some great advice here.

W113SL

jaymanek · « **Reply #49 on:** July 15, 2011, 14:32:43 »

Thanks but I think its now fixed with the new fuel pump.

I will now need to recheck my idle CO level.

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Author Topic: Intermittent bad misfire (Read 23950 times)

DavidBrough

jaymanek

jaymanek

IXLR8

UKSteve

jaymanek

jaymanek

DavidBrough

jaymanek

jaymanek

jaymanek

jaymanek

jaymanek

jaymanek

W113SL

jaymanek