PeachParts Mercedes-Benz Forum - Couple 'a questions: GP relay voltage; shake & tick

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Couple 'a questions: GP relay voltage; shake & tick

Okay, two things:

1) In an effort to figure out my '92 300D 2.5's hesitant start situation, I've finally gotten around to testing the GP relay. The plugs themselves are new and reaming has been done. The plug circuits test good for continuity. The battery tests 12.75V turned off, 12.26V with the ignition on, and >14V with the engine running. The relay pins test ~12.16V with the ignition on. My question is, is that good enough? Or should I be getting the full 12.26V from the battery?

2) The second thing is, can someone please watch the video and tell me if this OM602 look/sounds right? It seems to be shaking and ticking more at idle than I remember. I know to some extent that is par for the course with these old diesels, but I just don't know enough about them to know if I should be concerned or unfazed. I feel like the video doesn't quite capture the degree of shakiness, but it's the best I could do. Engine smooths out nicely on throttle. FWIW, engine mounts and belt shock are new. Fuel filters as well. Still planning a diesel purge and injector nozzles. Maybe lift pump, too.

https://youtu.be/lbbeo6zJWDg Sorry, shoulda shot the video in landscape orientation!

TIA.

In response to your questions:

1: You will never get full battery voltage at the GP's. You have losses in the relay contacts and the wiring. I'd say you're fine there.

2: Sounds like injector knock or "nailing" on one or more cylinders. When's the last time you had the injectors rebuilt? I recently chased down a nailing/knock on my SDL that was similar to yours, but only on one cylinder. Turned out to be a bad delivery valve (literally the valve, not the seals). It would nail like that up to around 12-1300RPM and sounded like someone hammering on the engine. Since the service it's smooth and quiet. Took care of the shaking idle too.

Quote:

Originally Posted by Diseasel300 (Post 3695732)

2: Sounds like injector knock or "nailing" on one or more cylinders. When's the last time you had the injectors rebuilt? I recently chased down a nailing/knock on my SDL that was similar to yours, but only on one cylinder. Turned out to be a bad delivery valve (literally the valve, not the seals). It would nail like that up to around 12-1300RPM and sounded like someone hammering on the engine. Since the service it's smooth and quiet. Took care of the shaking idle too.

AFAIK, the injectors are original. That's actually good to hear, since I was planning on taking care of that over the spring or summer anyway - it'll be nice if that's all it takes.