1995 S350, just finished doing a headgasket and confirmed that it has no bent rods. We've checked and double checked the IP timing using the window method as we don't have the Mercedes tools. These are the symptoms:

-Will not cold start or idle without aid
-Does not smoke while trying to start, but smokes a lot once we get it running
-When warm, it will surge at idle almost to the point of stalling
-When warm, only starts if you give it significant throttle
-It will drive fine at any temp, if you manually keep the RPM up at stops

What you you think? It's going to be a few days before I can work on it again, so if we could brainstorm some ideas I'd appreciate it.

Glow plugs.

Check the whole system.

And the ELR system.

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Color / smell of the smoke?

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Did you check and double check cam timing?

If you can't start it cold, how do you get it warm?

Sixto
83 300SD

Just make sure the injection pump tang is visable with the first cylinders cam lobes pointing generally upward. Or that the cam timing mark is where it should be when you see the tang.

You are describing enough symptoms that the injection pump timing could be very wrong. This is not a certainty but should be checked.

Get the injection pump lock tool and verify that the timing is correct. Looks are not enough. Some jobs can't be done without the tool.

Verify all the things already mentioned. Cam and pump timing, ELR, glow plugs, throttle linkages, etc.

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Did you move the IP or turn the crank while replacing the head gasket? If not, look elsewhere for the problem. IP timing won't change unless you moved the IP or removed the chain. Even letting the chain drop while the head's off is unlikely to change IP timing. For kicks, does the engine run better with the vacuum line disconnected from the shutoff actuator?

Sixto
83 300SD

I was just thinking that if an injection pump is 180 degrees off there in all probability will be more visable tailpipe emissions than when the pump was installed correctly.

Or in this case the removal of the head and reinstallation. Yes all will go back normally if the marks where lined up prior to pulling the head and a straight reinstall. Yet if an individual pulls the head without lining up the marks. In manuipulations to reinstall the head things could go wrong I suspect.

In any event it is just one thing I would check. Sixto is absolutly right though.

Car is now home in my shop. The car will only start with penetrating oil used as starting fluid and then smokes black horribly.
The car has a new cam and followers from FCP Euro.
Pulled engine as we thought it had jumped timing. Made an IP timing tool on my mill and all timing marks align up and IP timing is at 14deg ATDC.
My next step is to check lifters. I suspect there are some that are not collapsing far enough and holding valves open slightly.
Could they have sent me solid lifters for a hydraulic engine? I could not colaps them at all by hand like I could with the old ones but I thought they were just new.
I am a HD truck mechanic but have no experience with MB's in cars. Went to MB school for trucks in the late 80's but these are a different animal.

Still sounds like the injection pump may be way off. Not certain of course but how was the engine running before the head removal? Yet even if the injection pump is on the wrong cycle the engine will be harder to start but will usually start.

You are a working mechanic so I figure you got the timing right. Still you have some pretty extreme symptoms.

I do agree on checking those lifters as you describe them. . Rather than pulling the cam again a compression check should tell if they are functional .If you found them basically uncompressible when new and still dry they could have an issue . Yet I would wonder what it was at the same time.

To clarify how you confirmed timing, cam flange notch aligned with cam bearing tower bump shows within a tick of 0|T on the crank damper and IP RIV tang centered in the inspection port shows 14* ATDC on the crank damper, correct?







IIRC with the valve closed it should be possible though difficult to compress the lifter by pushing downward with a soft face object.

Sixto
83 300SD

Yes that is correct.
I tried pushing a .010 feeler gage between cam and lifters and it is a no go
used pry bar and pushed on lifters that are on base circle and inserted .010 feeler gage. Waited 30 seconds and tried to remove. Half I could pull it out half I can not. Old cam is ground on a 1.500 base circle and new cam is ground on 1.58" base circle
Wish I could do comp test with engine out but will try a cyl leakage test. To see if valves are actually sealing

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Bustin knuckles since 1981

Is the old cam still available for testing? Probably can't do that with the engine out though. I might have a good used .971 cam in the garage if push comes to shove.

Sixto
83 300SD

The old cam is in 3 pieces. The reason it got replaced. It was dropped.

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Bustin knuckles since 1981

How far are you from the MI/OH/IN line? I can loan you a .960 cam if you need one for testing. I also might have a set of used lifters. No spare injectors however, but if you need any comparisons I also have a '93 diesel W140.

You changed the cam lift? Did you check to ensure that the head was not machined, requiring the thicker gasket? Does the engine crank rhythmically to indicate even compression on all cylinders? Is it running on all cylinders? Does loosening any one of the injection lines change your smoke? It is possible that you have gotten dirt in an injector, and it is hanging open.

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