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C900 Bulletin Board
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Re: Long Cranking
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Posted by RayF (more from RayF) on Thu, 29 Sep 2011 09:33:19 Share Post by Email
In Reply to: Re: Long Cranking, Cmyles [Profile/Gallery] , Thu, 29 Sep 2011 08:27:33
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Jean Luc:

There's a way of putting in a pushbutton switch to let you run the fuel pump for a few seconds after turning ignition on, before turning key to crank, that cuts down quite a bit on cranking time, on cars where the fuel check valve at the tank has failed.

Some makes and models of cars run the fuel pump for a few seconds at key on; the C900 doesn't. ONLY WHILE ENGINE IS CRANKING OR RUNNING. That check valve holds fuel pressure in the line from whenever the car last ran. When it fails, since cranking draws so much current, the fuel pump even though on when cranking takes a long time to rebuild pressure in the fuel line sufficient to spray enough fuel to start.

(The theory of being on only when cranking or running is to save lives in crashes where a fuel line may be ruptured, so there's nothing to spray fuel out and make an inferno.)

There's a skinny lilac-colored wire from the ECU to the fuel pump relay that goes to ground to trigger the fuel pump relay. Tap into it, with a crimp connector to 1/4" female spade lug connector, buyable at many hardware stores, and then run a wire to a pushbutton switch like a doorbell, with a wire from other side of doorbell to the bodywork of the car. Then when you push that button the fuel pump will run, just ahead of cranking, and the car will start sooner - - if the failed check valve is your problem.

Replacing the check valve is also an option but it's expensive and it's amazing how many people break fuel lines when they try to do the job. The above-mentioned lilac wire is the only one that color leaving the ECU and it's easiest to get at it at the ECU connector end. The ECU and fuel pump relay are both up ahead of passenger's shin, behind the carpet panel. You need to take some metal trim strips off ahead of door, doorsill too maybe, and fold that carpet down to get at them. You don't cut the wire, just tap into it using a crimp connector. And don't use an on-off type switch, but a momentary contact one, as you don't want to leave fuel pump running all the time, for the safety feature reason above.



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