OM642 Misfire and White Smoke

[bembo449]

I don't want to scare you here but I have had this exact problem on a 2.7 terrano and it turned out to be a cracked head !

 

[hamodi]

But wouldn't that be burning oil or coolant? I have checked the oil and coolant and they both appear to be contamination free and level. It's diesel which is being dumped into the exhaust unburned - possible bent exhaust valve? Or somehow only the passenger side cam has jumped a few teeth - doesn't explain why only cylinder 5 is different in relative compression?

My first thought was swirl flap failure as these were notorious on BMW diesels which I had last but searching the forum it doesn't seem to be an issue on the OM642.

The other thing is a few months ago I had an turbo actuator fault code (it would sometimes jerk on kickdown). I removed the clip to disconnect the actuator from the vane mechanism and noticed it was difficult to move, probably carbon seizing up the vanes. I did run some turbo cleaner in the tank 2-3 months ago, I checked now and the mechanism is extremely easy to move as it should be. I'm just imagining all sorts of things like a vane broke off and somehow got sucked back into cylinder 5 from the EGR . Ahhhh I think I need to order a borescope to have closure.

 

[bembo449]

no it wasn't pal , a bent valve would defo mis-fire and probs poor starting too

 

[Doug1234]

Have you ruled out any crankcase breather issues and even egr ??

 

[hamodi]

Hi, the car was run with the Y-pipe removed in previous video shown, gases coming out of the breather hose seemed normal. Also removed oil filler cap while running to assess blowby - would these eliminate crankcase breather issues? The EGR I tried to check it last year but it was stuck on there, might give it another go removing it. I tried running it with injector 5 unplugged for a few seconds but smokes like this still - this is white and not blue, right? (I am colourblind!!)

 

[hamodi]

Injectors 4/5 swapped over and it’s still misfiring on cylinder 5

 

[LostKiwi]

Time to do a compression test using a proper gauge.

 

[alexanderfoti]

Star can do a comparative compression test as well.

 

[hamodi]

I've had it towed to the main dealers who'll be doing a proper compression test next week. The relative/comparative compression test was already performed at the Indy last month which showed a difference in cylinder 5.

 

[alexanderfoti]

I've had it towed to the main dealers who'll be doing a proper compression test next week. The relative/comparative compression test was already performed at the Indy last month which showed a difference in cylinder 5.

Why main dealer? They will do the same as the indy, for twice the price?

 

[Blobcat]

Why main dealer? They will do the same as the indy, for twice the price?

Probably do less for twice the price

 

[hamodi]

Yes, I know, but I also paid a lot at the Indy (10 hours) and it's still the same and been off the road for over a month. It's been frustrating and difficult not having the car running. Just trying something different as I feel a little helpless.

I did not have much confidence in the Indy as after 10 hours labour they asked me to change all the injectors at £300 each even though the relative compression test showed something up with cylinder 5, and it had been running perfectly before removing the high pressure fuel pump (I felt it would be more money wasted so perhaps the main dealer would be more targeted even though they cost more per hour)

I would appreciate any advice though as the dealers are awaiting my instruction on Monday. I could take it elsewhere but I would have to tow it yet again :/

 

[alexanderfoti]

Ah fair enough! I was just wondering why the swap to a main dealer, they will be doing the same things as the indy but at a higher cost. I dont feel you will get a different outcome with the main dealer.

That said, the indy could recomending things based on information we dont have?

We dont know the numbers that star gave. It could be that whilst 5 was lower, its not out of spec, etc.

Any garage (main dealer, indy or not), should be able to to carry out a compression test and give you a next step at least.

 

[hamodi]

Hi Alex, the values for the relative compression test were posted on the previous page, I have copied them below:
Cylinder 1 - 179 min-1
Cylinder 2 - 173 min-1
Cylinder 3 - 172 min-1
Cylinder 4 - 164 min-1
Cylinder 5 - 271 min-1
Cylinder 6 - 176 min-1

 

[bembo449]

Well that is pretty clear

 

[hamodi]

Removed all the injectors, tried to do a compression test but unfortunately my kit didn't have the right adaptor. Anyone know a link to the correct injector compression adaptor for mercedes?

What is strange is I removed the fuel pump relay and tried to crank it with the injectors off and I see this (oil?) coming out of cylinder 6? If anything, I would have thought cylinder 5 :/

Any ideas?

 

[Uncle Benz]

The copper washer that seals the injector to the cylinder head has failed. Get that replaced and the seat recut first. That might have been your issue all along with luck. They often leak unnoticed for a while before they get this bad

 

[hamodi]

The copper washer that seals the injector to the cylinder head has failed. Get that replaced and the seat recut first. That might have been your issue all along with luck. They often leak unnoticed for a while before they get this bad

Hello, I think you mean if the injectors were still in place and this happened but this is happening with the injectors removed.

 

[Uncle Benz]

That'll teach me to use my phone for browsing! My eyesight is poor at the best of times! Either there is a lot of diesel in that pot or something else is getting in there. While you have the injectors out I would get them tested for dripping. Could be a lot of unburned diesel if the injector is dripping.

 

[LostKiwi]

Put a kitchen towel over the hole to catch what's being ejected. You should quickly determine what it is from the smell and appearance.