10-05-2012, 10:53 PM
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10mm MW
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Join Date: Sep 2008
Location: Michigan
Posts: 794
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Quote:
Originally Posted by oso
Yes, I have disconnected the circuit at the back of IP on many occasions and that is exactly what happens: idle drops and stops being erratic. I will try to follow the wire I guess. Thanks for all your input.
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If I recall correctly, there was a member on another forum that had the same idle issue.
As it so happened, one of the members has a pump shop over seas, (not sure where but his screen name is Dieselmeken), and he said that the electronic controlled M pumps are susceptible to the Delivery Valves wearing out which results in more fuel in injected at a given rack setting than the computer is calibrated for.
So what is happening is, the DV allows more (unregulated) fuel to be injected causing the engine to rev up, the computer sees this and yanks the rack back causing the engine speed to drop, and then returns the rack to where it should be for the correct idle speed, but the DVs are still causing more fuel to be delivered and the cycle starts all over again.
When you unplug the pump from the computer the idle stabilizes out because the computer is not trying to control the idle speed with DVs that cause delivery rates outside of the computers calibration.
He said replace the DVs and all will be good.
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