OM 615 idle speed to high
 

Mercedes OM615 with a pneumatic governor. Starting up from cold it's about 450 rpm then over about 10 minutes it climes to just over a thousand as the engine warms up and there it stays. I have tried disconnecting all the linkages and the adjusting screw is wound right out. Nothing i've tried brings the revs down. Im thinking its something to do with the governor but I don't want to mess around with it without knowing what i'm doing.

Martin

A warm diesel idles faster then when its cold

Sent from my SAMSUNG-SM-G890A using Tapatalk

Inside the regulator there is a membrane which on this forum is often referred to as the "pig's bladder" - when this breaks / has a hole in it you get the symptoms you describe.


Check the plumbing between the regulator (back of the injector pump) and the throttle valve at the air intake before you start looking at the regulator.


To test the system you can use one of those expensive Mity Vacs or the alternative boxed in red plastic offerings from the bay of ee to see if it holds any vacuum.


To the best of my knowledge the spare parts are most likely to be found at the dealership rather than other place

If I remember rightly 450rpm is a bit on the low side but I wouldn't adjust anything until you get this revving higher when warm problem fixed

Thanks I'll check the plumbing out. What should I look for in the throttle valve ? I noticed there is a bit of play in the butterfly valve shaft could that affect the vacuum?

Martin

If there is a bit as in a fraction of a mm then I guess it probably won't have too much of an influence on the system. If it is flopping about like washing on a line then you should already know the answer!

I encourage you to look in the FSM to see how the system works and how it is meant to be set up. It is a very well written book and free to download on the startek site.

Does it burn a lot of oil or is the crankcase possibly overfilled?

Wondering if it could be starting to runaway due to burning engine oil as fuel. If it stops climbing and holds steady then it probably isn't a runaway.

Good luck!!!

Governor Diaphragm Test
http://www.peachparts.com/shopforum/diesel-discussion/313733-74-240d-grey-smoke-questions.html

Governor Diaphragm
What are the symptoms of a bad IP Governor Diaphragm - PeachParts Mercedes-Benz Forum

Replaced the vacuum line to the IP which didn't make any difference. I've just had a vacuum gauge on the guvenor end and it won't hold a vacuum so looks like that is the problem. I'll take the IP off and get it checked out.
Thanks for your time.

Martin

Martin-
I don't recall for sure, but I think you can replace the diaphragm without removing the whole IP from the engine. For me, that sounds easier that removing and replacing the entire injection pump, so I thought I would suggest that you look into it.

X2


Absolutely don't remove the IP!


See the links posted by Diesel911 or the FSM