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Thanks for all the help with the problem. The fuel pump is not working because the pump relay does not operate. I have replaced the relay but it still does not work ( the pump is OK } I see in the Haynes manual? there is a turbo over pressure switch in the relay operating circuit. Could this be the problem or is it the ECU, and where is this switch?
thanks
Ian
 

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I'm not sure of the detail Ian, and can't find any useful diagrams
... but certainly if the pressure switch is faulty, then yes it does interrupt the supply to the fuel pump. It coudl be either the switch or the ECU.

Given that it's a failsafe circuit, it will almost certainly rely on continuity to enable it. Thus, if there is corrosion in a contact/connector that gives a high impedance joint, it could well cause the ECU to think there is overboost.

I'm afraid I'll have to leave it to someone else (hopefully) who actually knows where to find the switch though


it may just be a
 

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Hmmm....have you checked the crank position sensor - or, perhaps the wiring from the sensor to the ECU The engine must turn 150 rpms for the fuel pump relay to energize and fire the DI. This or a bad DI could be sending an error signal that shuts down the pump relay. If I'm not mistaken, I think the pressure switch you're referring to is the MAP sensor - that will cut-off fuel (as most 9000 owners have experienced this anti-
) if the boost pressures get too high.
 

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I hadn't thought of the CPS myself, so it is a possibility.

Being a '91, Ian'S car is pre Trionic and thus doesn't have a MAP sensor. Instead, rather like C900s, they have an overboost pressure switch, preset to a certain value.
 

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I'm sorry, I thought he had a CS.....well, in that case he might also want to check the knock sensor, too, as both sensors can give error signals to the ECM (Jetronic?) and shut down the pump relay. Those wiring shields can wear and ground-out, which will definitely shut down the pump relay....hth
 
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