Adjusting idle speed

martinriches

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8 Jun 2005
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Mercedes OM615 with a pneumatic governor. Starting up from cold it's about 450 rpm then 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. Just about to call the mechanic in but maybe there is something i've missed.

Martin
 

david_bagshaw

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5 Jun 2001
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Have you checked there is no air leak on the air pipes to the governor. I know when it is disconnected on some throttle body control systems it goes into max fuel, so perhaps a small crack on a union allows the revs to rise as it gets warm.
 
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