Mercedes Diesel Misfire After HG Replacement

[Astro14]

You would think you would have more exhaust smoke from a totally dead hole. Like said, could be a valve not seating.

I assume you paid this guy a lot of money, thus the legal recourse?

If the injector is plugged with rust - not going to be a lot of smoke…

 

[Astro14]

@JHZR2 - How long did this sit outside? If you had a problem in 2019, and he did the work, are we talking four or five YEARS outside?

 

[JTK]

If the injector is plugged with rust - not going to be a lot of smoke…

If that's the case, it would be worth putting a working fuel injector in that cylinder. Perhaps then a few suck, squeeze, bang and blow cycles will free the rings or at least take some guessing out of the equation.

 

[supton]

That's a lot of rust in the tank. I'd check all the other places that might have problems (brake lines, undercarriage, etc) and scope out this project. Is it just a new tank, new fuel lines and a new injector? Head work too?

You sound like you are coming into a very busy time of life. Is this a project you really want to dig into? Now or ever? If you want to save it, might it be best to just mothball this in your garage, fog everything and leave it in one piece? In 5 or 10 years, come back to it. [I envision a worst case scenario here where you take it all apart, life gets in the way, and now you have a dismantled car that sits for five years, in boxes, for a day that might not come.]

At the very least I'm not sure I'd let it run on whatever is in that tank, rig up a boat tank or whatever.

 

[JHZR2]

I'm going with bad fuel causing the miss or the valves on 6 are out of adjustment.

Bad fuel doesn’t affect compression. I don’t have evidence that there is any issue with the fuel just from seeing it in the prefilter. I do plan to run off of fresh pump fuel when I have a chance. Yesterday was a rush to get the car out of where it was. It wasn’t going far so I knew that a few filters spares would do the job.

None clogged up, so that’s a good sign.

If it were mine, and I had done the compression numbers (I thought the mechanic had done that, and stated that they were low), I would pull the head. It’s a pain, but can be done in a day.

The fact that this car:

1. Ran OK when you brought it in.
2. Then sat for years.
3. Has rust on the #6 injector

Leads me to believe that you had water get in to #6. Which can rust the rings to the pistons as well as to the bores.

But oh, that fuel tank and cap. I would remove the fuel tank (not easy on this car if it’s like the ones I have owned) and have it cleaned and coated inside, or just replaced with a good one. Then replace the filter and clean the lines.

Even if you solve the running issue - that fuel tank is going to continue to be a problem with all that rust.

I’ve seen other fillers like that. Definitely needs a neck.

I had another car once that had a rusty neck like that. I added a fine Racor in lieu of the OE prefilter. To my surprise I never saw a speck of rust in there. I guess it could be lodged in the tank screen, but never anything else.

So I need to be real careful but also am cautiously optimistic. But will drain the tank, replace the filler neck, scope out the tank, etc.

WRT the #6 injector, if it was wet up top on the injector body (rest of the body isn’t rusted), that wouldn’t let water in. Water would have to come from the tank, but then other parts of the injector would be rusty… I think (???).

I am more concerned with what the white junk is. If it’s silicate, then the “how” is more suspect. The head wasn’t cracked before, and the 3.5L engines don’t suffer cracked heads…

You would think you would have more exhaust smoke from a totally dead hole. Like said, could be a valve not seating.

I assume you paid this guy a lot of money, thus the legal recourse?

Yes, whether water in fuel or something else I would think it would be more smoky.

I am concerned if something is leaking into the cylinder. Twice when hot restarting I sensed that “pause” as it turned over. My wife said it had a bit of white and black smoke when it did that. No other time. The system didn’t build pressure but I’m not convinced that matters as my other om601/2/3 cars have not built pressure when hot.

I’m not out money for parts or labor. So there’s that.

Ignition on a gas engine or pump timing on a diesel cannot effect compression but cam timing sure can but it would probably effect more than one cylinder. Is this the engine you were doing lifters on? It still has some noise that sounds like it is coming from the top end.
A collapsed lifter, broken or weak valve spring or bad cam lobe can cause not only noise but lower compression on one cylinder, you cannot go on looks alone camshaft lobes need to be measured.
You need to check everything carefully and thoroughly before tearing the head off or condemning the engine.

The lifters are on another 1991 - the w124 300d. I’m pretty sure now that it is related to the IP/delivery valves, not anything on the engine, since the lifters were replaced, injectors swapped, etc.

If it was timing, and I didn’t crash a valve into a piston, wouldn’t it travel? Being off by an again link or two between the cam and the crank would cause the timing to change, wouldn’t it?

Totally agree on checking everything over. Thus far I take that to include:

1) verify timing via the balancer and crank marks.
2) verify timing via the balancer and IP tang.
3) validate fuel quality coming into the IP (rust, particulates, cloudiness)
4) swap injector #6 with a different one to verify operation on that cylinder
5) with engine operating, do blowby test (glove on oil fill cap or similar) to verify if large amounts of air is passing through
5) perform leak down test on injector 6, and identify location of air leakage.

Any other recommendations?

 

[JHZR2]

@JHZR2 - How long did this sit outside? If you had a problem in 2019, and he did the work, are we talking four or five YEARS outside?

Sigh, yes.

 

[JHZR2]

I'm going with bad fuel causing the miss or the valves on 6 are out of adjustment.

Hydraulic lifters, and low compression, so not sure that could be the case.

 

[JHZR2]

That's a lot of rust in the tank. I'd check all the other places that might have problems (brake lines, undercarriage, etc) and scope out this project. Is it just a new tank, new fuel lines and a new injector? Head work too?

You sound like you are coming into a very busy time of life. Is this a project you really want to dig into? Now or ever? If you want to save it, might it be best to just mothball this in your garage, fog everything and leave it in one piece? In 5 or 10 years, come back to it. [I envision a worst case scenario here where you take it all apart, life gets in the way, and now you have a dismantled car that sits for five years, in boxes, for a day that might not come.]

At the very least I'm not sure I'd let it run on whatever is in that tank, rig up a boat tank or whatever.

I’ll disagree on the rust part.

Nasty filler neck? Definitely. Rust in the filler neck? For sure.

Obviously the logic is water in the fuel. Yet, the car fired up immediately; and its operations didn’t change after that. Same misfire the whole time.

The rest of the car is still rust free from my initial look. It didn’t see salt, it did see rain, but lots of these cars sit outside or live in a field before being brought back to life. Not saying it’s good, but I don’t think anything else is dire. It holds tight, no water leaks anywhere. Drains were clear.

You’re right, time is an issue. More and more. And I have lots of cars, and other things going on, which is what distracted me from this project.

Thing is, I don’t see that getting any better for the next 18 years. So I might as well address now and then decide.

Part of me wants to pull the head and do that. I don’t think I’d be up for pulling the engine, but I would consider the head job. What’s the worst that can happen? I then decide to sell the car apart (not worth much less like that than now), or back together and learn from the job?

When I gave the car over I didn’t have the number of garages or the know how for all the engine work that I do now. So that’s a benefit for me to try to schedule it in and do it… even if during oppressive summer heat. I can’t imagine it sitting in current form will do anything good for it.

 

[JHZR2]

If the injector is plugged with rust - not going to be a lot of smoke…

When doing the compression test, the fuel return line has to be disconnected. The fuel that came out of there looked clean and fine.

If one injector clogged, the others would too. I don’t see how only one would be damaged.

That said, who knows what the injector status is. Since I have another good popped 135bar injector, that’s an easy swap. I guess I could also leave the injector out and just crank the engine to see if it sprays into a jar…

 

[Trav]

Bad fuel doesn’t affect compression. I don’t have evidence that there is any issue with the fuel just from seeing it in the prefilter. I do plan to run off of fresh pump fuel when I have a chance. Yesterday was a rush to get the car out of where it was. It wasn’t going far so I knew that a few filters spares would do the job.

None clogged up, so that’s a good sign.



I’ve seen other fillers like that. Definitely needs a neck.

I had another car once that had a rusty neck like that. I added a fine Racor in lieu of the OE prefilter. To my surprise I never saw a speck of rust in there. I guess it could be lodged in the tank screen, but never anything else.

So I need to be real careful but also am cautiously optimistic. But will drain the tank, replace the filler neck, scope out the tank, etc.

WRT the #6 injector, if it was wet up top on the injector body (rest of the body isn’t rusted), that wouldn’t let water in. Water would have to come from the tank, but then other parts of the injector would be rusty… I think (???).

I am more concerned with what the white junk is. If it’s silicate, then the “how” is more suspect. The head wasn’t cracked before, and the 3.5L engines don’t suffer cracked heads…



Yes, whether water in fuel or something else I would think it would be more smoky.

I am concerned if something is leaking into the cylinder. Twice when hot restarting I sensed that “pause” as it turned over. My wife said it had a bit of white and black smoke when it did that. No other time. The system didn’t build pressure but I’m not convinced that matters as my other om601/2/3 cars have not built pressure when hot.

I’m not out money for parts or labor. So there’s that.


The lifters are on another 1991 - the w124 300d. I’m pretty sure now that it is related to the IP/delivery valves, not anything on the engine, since the lifters were replaced, injectors swapped, etc.

If it was timing, and I didn’t crash a valve into a piston, wouldn’t it travel? Being off by an again link or two between the cam and the crank would cause the timing to change, wouldn’t it?

Totally agree on checking everything over. Thus far I take that to include:

1) verify timing via the balancer and crank marks.
2) verify timing via the balancer and IP tang.
3) validate fuel quality coming into the IP (rust, particulates, cloudiness)
4) swap injector #6 with a different one to verify operation on that cylinder
5) with engine operating, do blowby test (glove on oil fill cap or similar) to verify if large amounts of air is passing through
5) perform leak down test on injector 6, and identify location of air leakage.

Any other recommendations?

Sure, the cam timing would be off. This is a OM603?

 

[JHZR2]

Sure, the cam timing would be off. This is a OM603?

Yes. This 1991 (I have three 1991 cars) is a 603/350SD.

So if timing was off it would revolve the misfire between cylinders… until a valve clashed into a piston, no?

Trying to understand, like if the low compression cylinder could revolve as the timing location changed.

 

[meep]

I used to own a 1957 bel air 4 door with the 283 and powerglide. It was my great grandmothers, then belonged to my grandparents. They gave it at times to my mother, then my aunt. They eventually gave it to me through my mom. This car had family history all over it. Sometime around 2002, I and we sold it. It was getting worse, not better, in my hands due to time, space and just not being able to find more and more money for things I’d need to farm out. It was hard to do.

Our mailman bought it, and he and his son performed a full frame-off restoration. I have wonderful memories of the car, but we made the right move.

I LOVE the allure of a diesel Benz. LOVE. I barely have the patience for a 6 year old ford truck.

 

[JHZR2]

Pull the head, investigate further. I dont think theres much to gleam from that ugly injector. Your narrative basically tells me that the mechanic's work is likely sketch and he probably didnt do the HG correctly.

So I was thinking a bit more about the #6 injector.

The white residue was between the injector and its plastic cover.

Not sure why and what it is. But as I’ve noted, the mechanic said he used white lithium grease in the bores.

I wonder if he greases the head bolts… and that got in?

FSM says to oil the bolts.

If they greased them, it could be a remnant of that perhaps.

There is a head bolt nearby.

I also noticed this in the area, which may be more telling

Look at the black (oil?) and white (grease or coolant?).

I think this is between cyl 5-6 based upon the location of the cruise control arm… I don’t have a good photo handy of the exact location.

 

[JHZR2]

Edit, I want to say that white residue is between 4-5. I also found a pic of the engine with the head off, and the head.

Note that white grease on the bore under the edge of the rag…

 

[Exhaustgases]

It sat for years ! The moisture in the fuel tank is from condensation, I'm sure the tank has to be vented so, air containing moisture, etc etc.

Grease in the cylinders? That doesn't make sense that it would still be there after he puts the head back on, and grease, there is much better stuff to use for that purpose. Sounds like a back yard mechanic not a shop.

If the old diesel is still in it that will not help anything, it degrades.

 

[cptbarkey]

Lithium can be used for o-rings, and might have been used to install the injectors. I think its a red herring.

 

[JHZR2]

It sat for years ! The moisture in the fuel tank is from condensation, I'm sure the tank has to be vented so, air containing moisture, etc etc.

Grease in the cylinders? That doesn't make sense that it would still be there after he puts the head back on, and grease, there is much better stuff to use for that purpose. Sounds like a back yard mechanic not a shop.

If the old diesel is still in it that will not help anything, it degrades.

Yes; this isn’t my first MB diesel. The tanks have some amount of breathing, and the spot that cools first is the filler neck, so moisture can build there.

That’s what we’re seeing. I’ll scope the tank at some point, and I’ll also be draining the tank this weekend, but the fuel in the system is clean and clear. If there is water in the tank, the main filter is separating it sufficiently that this is NOT the issue. There is no particulate in the prefilter, and the fully filtered fuel is clean and clear. I’ve had other diesels that have had fuel sit for extended period. It’s more stable than gasoline, and it works fine. It fired right up after sitting with a dead battery for I don’t know how long.

WRT grease, I don’t know. The shop, yes it is a shop, has been in business forever. I used them in the early 2000s. Highly knowledgable old guy. Can’t find good help, can’t work, so here we are.

It is what it is at this point. Scrutinizing what they did doesn’t help. Laying out the path ahead and investigating/fixing does….

 

[JHZR2]

Lithium can be used for o-rings, and might have been used to install the injectors. I think it’s a red herring.

I tend to agree. Had it not been for that old photo I just posted, I might not have been as aware of what it kind of looked like. But you can see from that photo and see it was sprayed and coated.

The only question would be, could it have been forced out of the prechamber and onto the injector? Could it have been present in the cylinder, and either held grit, or just created carbon and gunk that stuck the rings?

Time will tell as I do leak down and a borescope if needed…

 

[Astro14]

Actually, I think scrutinizing what they did is part of the forensic analysis. I have to know what was done in order to help figure out what you’ve got here.

 

[JHZR2]

Actually, I think scrutinizing what they did is part of the forensic analysis. I have to know what was done in order to help figure out what you’ve got here.

I don’t know that there will be much good info to be honest. I have a document with all the parts. It’s handwritten. I feel like this has the ability to turn into “telephone game”.

This has turned into a mess. I can try to contact him and verify what else was done, I may or may not get all the info I need.

What I have in my notes is that the head was off twice. There was a misfire the first time due to a bad valve seal/seat (?). He did checks, pulled the head, had the machine shop check it, they found a slight leak, supposedly fixed it. So I was told. Head back on, car still had a misfire. Cylinder #2. For a low mile 603 and the misfire NOT in cylinder #1, and the fact that it ran perfectly before I brought it in (just a seeping HG letting oil go into coolant), we were pretty confident it’s NOT any sort of rod bending situation. He supposedly measured it.

I was told that the second round, injectors had been swapped. Only cylinder 2 showed no change when fuel line was cracked. Per my notes, it runs smooth and strong around, it just shakes badly at idle.

I guess it could still be an issue with the workmanship on the head, though one would hope that was resolved.

What I don’t have good clarity on is the diffeeence between issues with injector/cylinder #2, and what I’m seeing on #6. Injector 2 is a new Bosch injector. I know that from when I pulled it for the compression test. It was the “lowest” relative to the group that is not #6.

Maybe it is a botched head job that wasn’t properly repaired??

Leakdown should verify that, right? If I put cyl 1 at TDC, then cyl 6 should also be TDC. Then I do leakdown on cyl 6, and I’ll see air either in the coolant bottle, out the exhaust, or out the intake, right?

With such low compression in that one cylinder I assume it will flow decently and reasonably loud in one of those directions if I feed it 75-100 psi air, right?

Thanks!