rebuilt 300D not running right, odd noise - PeachParts Mercedes-Benz Forum

Larry Delor · #1 05-22-2002, 08:36 AM

Hello folks!

I recently purchased a rebuilt engine for my 300D. The mechanic who installed it is not a diesel expert, but I believe in his mechanic skills. Seems we have run into a snag.
He called me up the other day to tell me he had it running, (he had taken quite some time getting the injection timing right), but, he said that it ran rough, especially cold.
Here is what I observed:

*The engine starts, but runs very rough-it even stalls a few times, but will start back up.
*When increasing the throttle to high rpm's it runs very smooth and even.
*When at idle (after a few minutes of warming up), there is an odd noise that has me wondering what it is...I can hear it distinctly through the air cleaner...it sounds as though one of the cylinders is going the wrong way... like someone banging on the bottom of a coffee can with a wrench (in regular intervals).
*There is a lot of grey/blue smoke.

I was thinking valve timing, but then wondered if that wouldn't cause bent valves. I don't know if the injection timing being off would cause these symptoms.

Any comments/suggestions are welcome

Nate Stanley · #2 05-22-2002, 09:39 AM

Did he also get into the fuel injectors?

#3 05-22-2002, 09:50 AM

Hi: The first time I worked on a Volkswagon diesel I had a problem like yours, and I was stumped. Not running good at idle, noise, black smoke out the pipe. It must of been by the grace of God that I tried pulling out the cold start advance that it was equiped with. ( the engine was warm and I was going down the road) It advanced the pump 21/2 degrees. What a difference, I couldn't believe it. The car took off, good power, no more smoke. I went home and retimed the pump, solved everything. Might be worth a try. I know it isn't easy to get the timing right with the 1 drip per second method, try to advance it a little. I usually make a mark across the block onto the pump, then I move the pump a little, about 1/4 inch. If it makes a good difference your on the right track, if not try 1/4 inch past your mark the other way. If it doesn't help set it back on your mark, recheck the valve clearance, if that don't fix it maybe someone has an idea for you. I find great help on this forum all the time.

Good Luck

P.E.Haiges · #4 05-22-2002, 10:41 AM

Larry,

I would check the injectors. Loosen the flare nut (the nut that connects the injector lines to the injector body) on the top of one injector at a time to see if the noise goes away. Fuel oil will leak out and the engine will miss fire, but that's OK, you are looking for the knocking to stop. If you find that the knocking on one cylinder stops, that is the one with the bad injector. If you want to be sure it is that injector, switch the suspect injector with another one and see if the noise follows the suspect injector. If it moves, its a bad injector. If not its something else.

If its not a bad injector, you might check the valve lash with go/nogo gages to make sure that were set right. Valve timing is determined by the wear in the timimg chain. It can't be off a tooth or the engine would not not turn because the valves would hit the pistons. A rebuilt engine should have a new timing chain in it so valve timing should be right on zero.

You will need a 1 1/8 or 27MM deep socket to remove the injector. This socket will also work on the crankshaft nut to turn the engine by hand to adjust the valves.

P E H

Nate Stanley · #5 05-22-2002, 11:07 AM

The reason I asked about the mechanic getting into the injectors was-- last weekend I was disassembling mine to clean them, and accidentally got al part inside the injector upside down.

It's a piece that sits between the injector spring and the pintle. The flat side should be up, the conical side down.

With this internal part upside down, the symptoms I had were much like the ones you reported. Lots of noise and smoke, and it did smooth out at higher revs.

Cracking the lines as P. E. Haiges mentioned isolated the bad one, a quick disassembly and correct reassy fixed the problem with no harm done.

BTW- 27MM= 1-1/16" for that socket.

Hope this helps!