W124 OM602 Start Up Missing, OK after it warms up. - PeachParts Mercedes-Benz Forum

JamesDean · #1 09-11-2014, 01:33 PM

So my OM602 in the 300D has been misbehaving in the mornings.

It'll start up fine and then a few seconds into running it will start to miss:

Here is a video, its not as bad as it has been but you can see get an idea of whats going on.
https://www.youtube.com/watch?v=_uRKNe0ZMM8

Any thoughts on a cause?

I've recently re-done my delivery valve seals and replaced the #4 and #5 injector hard lines. The problem existed before all of this work and still exists after.

I have about 293K miles on it. Injectors are original and are slated to have their nozzles replaced, tested and balanced by greazzer when I have my 190E's water leak resolved.

tjts1 · #2 09-11-2014, 01:54 PM

What about a hot start, is it much smoother?

When doing a cold start, wait a full minute after turning the key to start the engine even after the GP light goes out. Does does it idle much smoother in that situation?

JamesDean · #3 09-11-2014, 01:59 PM

I will have to test these to verify but from what I can recall a hot start is fine. No issues.

I will try waiting longer and report back.

For what its worth, the glow plugs were replaced in December of 2012. I had one or tow bad. It was miserable to start cold.

tjts1 · #4 09-11-2014, 02:02 PM

The way the GP relay operates, once the light goes out the GPs stay hot for up to 1 minute or 30 sec (i think it depends on model year) IF you don't crank the engine. You can disconnect the big 5 pin plug off the GP relay and check the resistance to ground on each of the pins in the plug to see if any GPs have infinite resistance. Should be ~4ohm for good GPs. Monark GPs have a reputation for early failure in case you used those.