M103 Head gasket replaced now won't start - PeachParts Mercedes-Benz Forum

manc · #1 03-09-2009, 10:24 PM

I just did head gasket job on my friend's '89 300TE with an M103 engine. The job went fine after reading all of the great posts on here. Now the problem, it won't start. The engine whirrs when cranked but won't fire. Details: We sent out the head and had the whole deal (surfaced, new stem seals, pressure-tested), the timing chain was left in place.

I believe it must be a timing issue. I have the Brookings manual but can't seem to get the info I need.

I am just a backyard mechanic so the more detail the better.

Any ideas? Where should I start?

Thanks in advance, Phil.

tinypanzer · #2 03-09-2009, 11:01 PM

My suspicion is that you forgot to hook something back up afterwards, or an electrical connection was damaged during removal or replacement.

Coolant temp sensors are at the top of the list, since you have to pull those to do the head. A bad temp sensor will make it very difficult if not impossible to start.

I posted a thread here (you can search for it) that has the test procedure and the comparison charts.

But, I would start by going over every connection both vacuum and electrical. You probably missed something.

wbain5280 · #3 03-10-2009, 12:48 AM

Are the spark plug wires correctly installed? After that, is there spark? Is the wiring harness that snakes across the top of the engine hooked up right?

When you say whirr, do you mean turns over correctly with compression but does not fire or turns over really fast with no compression?

When you tightened the head, did you do two 90 degree turns of the head bolts to tighten them? (just asking)

manc · #4 03-10-2009, 02:36 PM

Thanks Guys!

I am going over to the car in a few minutes. I will do a thorough check again. We were extremely careful and followed the directions completely when bolting down the head. You never know though, sometimes when you see light at the end of the tunnel things can get overlooked.

We checked the spark and is getting a good spark. Removed one of the plugs again after trying and the cylinder as well as the plug smelled like fuel.

I thought when we tried to fire it up that if the timing was off that it would at least make a sound like it was trying to fire but here it just spins. It does spin at the right speed but no firing or bucking sounds just a steady whirring.

Thanks and I'll keep you posted. Phil.

hookedon210s · #5 03-10-2009, 09:57 PM

Camshaft timing is suspect. How did you ensure it didn't change when you removed the head and reinstalled it? Check it to make sure it is correct. You can also spray a dab of starting fluid into the intake manifold and crank the car to see if there is any sign of life. If not and there is spark at the plugs camshaft timing is suspect. Crossed plug wires will usually get some kind of response even if its not the one you are seeking (backfiring). Mark

wbain5280 · #6 03-11-2009, 01:02 AM

My engine did the same thing, it just cranked and would spin. It did start.

Jump the fuel pump relay socket to power the fuel pump, pins 7 and 8 I think, and push down on the CIS airflow plate to get the fuel moving in the injector lines. You will have to remove the air cleaner assembly.

agood · #7 03-31-2009, 02:38 PM

Is there a DIY on replacing the Head Gasket someone on this board?

ps2cho · #8 04-01-2009, 12:45 AM

http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/01-4150.pdf

Head Gasket ^ Here ya go.

It is very important to make sure the timing was right before attempting to start the car.

Here's the PDF to set it correctly
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/05-2150.pdf

Gilly · #9 04-01-2009, 05:00 AM

Since the ignition rotor attaches to the front of the cam, if the cam is right the ignition rotor should be close, or close enough. Wanna recheck cam timing? Does it seem to have compression, you might want to test that. I suppose the rotor bracket migh be misinstalled, although on second thought you probably couldn't get the dist cap on right if you messed that up.

Gilly