fuel pump priming

[Ozstyle]

Hi all,

appreciate any ideas on this. With the ignition turned on the fuel pump primes but does not turn off after a few seconds as it should. I can here and feel the fuel relay click off but the fuel pump continues to run. When I pull the key out of the ignition the pump continues to run until the ECU relay switches off. If I turn on the immobiliser then nothing at all when I switch the ignition on - as it should be. The car (94 500) runs fine. I have searched the Griffith forum and there is a single mention of this but no outcome was ever submitted.

thanks,

OZstyle.

[Guillotine]

there's a pressure switch on the front of the rail, could be that.

or the ECU, wiring etc.

should turn off after 3 as you say.

andy
94 500

[GreenV8S]

I have had these symptoms in the past but only very occasionally. The ECU ran the fuel pump continuously, and also the car wouldn't start. In my case the problem always went away if I switched off, waited a few seconds and switched back on again. It probably indicates a fault within the ECU itself, no idea what, but power cycling it has always cured it for me so far.

[larrylamb11]

It sounds to me like the fuel pump relay has died internally and is still maintaining the circuit... but that is just a guess. From what you describe it is still working correctly.... ign 'on', pump primes, you feel the relay click 'off' but the pump runs on - so it sounds like the ECU is telling the relay to 'switch off' but the relay isnt (until the main feed power is killed when the main relay switches off). That would certainly be my first port of call - test the relay for correct operation.

[griffter]

My guess would be something along the lines of the immobiliser unwittingly earthing the switched control earth of the fuel pump relay. e.g. if the ecu should control the earth so as to switch the relay and fuel pump on, but the immobiliser is earthing it as well/instead, it wouldn't make any difference to the fuel pump what the ecu does. It's only a guess - all depends on how the immobiliser works, how it and the ecu are connected to the fuel pump relay etc - but it's the kind of thing I'd start looking at.

[Ozstyle]

Hi,

old thread but just to finish the topic. Cleaning the footwell loom up the other day and could not find the fuel cut off switch. Thats because it has gone, looks like some time in the past its been removed and the fuel pump wire connected to an ignition live. Checked the cut wiring with mulimeter (used sh bible diagram)and all powered up and down as expected. Made a temporay connection, so now pump primes for 2 seconds with ignition on and car runs fine when fired up. Just got to wire in a new inertia switch.

Ozstyle