No volts at fuel pump - advice please

[taylormj4]

Hi all,
Car would not start and no fuel pump noise, so checked the connectors to the fuel pump and found no volts. Have tried changing over the two silver relays on the ECU wiring loom (as suggested on other threads) but pump still did not fire up. Have checked fuel cut-off switch (black box behind dashboard access panel) and no button appears to have pooped out.

Any ideas where the problem lies?

Have traced the yellow wire from the pump back to a connector in the nearside B-post but where does it go from there?

Cheers,
Matt

[that daddy]

Matt have you checked the fuses?when you checked the feed to the pump did you realise the pump only primes for a couple of seconds when the ignition is switched on,because it detects the engine is not running then shuts supply to the pump,just a thought.

[shpub]

It's also controlled by the immobiliser.

[that daddy]

shpub said:

It's also controlled by the immobiliser.

yes forgot that one..doh it is sunday,thanks.

[taylormj4]

that daddy said:

Matt have you checked the fuses?when you checked the feed to the pump did you realise the pump only primes for a couple of seconds when the ignition is switched on,because it detects the engine is not running then shuts supply to the pump,just a thought.

Ah, right. So I need to check for volts in the first second or so after switching IGN on. What takes over control of the pump then, i.e. where does the feed come from - through another relay ?

Steve - how do I check whether the immoboliser is sending feed through (location of units / wiring etc).

PS. Checked fuse - all Ok.

It's a 1997 Chimaera, with the 5 / 6 relay panel and the two 'floating' silver relays.

Matt

Edited by taylormj4 on Sunday 28th January 11:27

[antonyj]

taylormj4 said:

that daddy said:

Matt have you checked the fuses?when you checked the feed to the pump did you realise the pump only primes for a couple of seconds when the ignition is switched on,because it detects the engine is not running then shuts supply to the pump,just a thought.

Ah, right. So I need to check for volts in the first second or so after switching IGN on. What takes over control of the pump then, i.e. where does the feed come from - through another relay ?

Steve - how do I check whether the immoboliser is sending feed through (location of units / wiring etc).

PS. Checked fuse - all Ok.

It's a 1997 Chimaera, with the 5 / 6 relay panel and the two 'floating' silver relays.

Matt

Edited by taylormj4 on Sunday 28th January 11:27

The ecu controls the pump by switching the FP relay.
When you turn on the ignition it primes the pump for a few seconds and then stops it, as soon as the car is running the pump is then run continuously,

[taylormj4]

Thanks all,
off to look at the underside of my car for a bit then and try not to get too dipressed about all of the flaking paint and rust on the chassis members.

Matt

[GreenV8S]

Now you understand how the pump is supposed to run and once you've checked the obvious (fuses, relays inertia cut-off etc) the next logical thing to check would be power to and from the relay and the control circuit to and from the relay. Fot reference, the relay switches the 'earth' side of the relay control circuit so you should see a healthy 12v permanently on the other side as long as the ignition is on. I'd also do a sanity check that the battery isn't dead and that other ignition-switched ancillaries still work.

[spend]

As PeterH has often advised I'd try hotwiring the pump first to make sure it works (& make sure the ground is OK).

With the 'hotwire' cable in place, you should be able to do a continuity check up to the trailing fuse. This will iscolate wheteher its the ecu/relay/fuse or inertia switch / immob(not sure if it affects all cars) / wiring /pump.

The trailing fuse is actually quite a handy test point (you can just stick a multimeter in it or a test bulb -> chassis.

BTW: Im assuming your 'no volts at fuel pump' is misleading, cos you seemed to realize part way thro the thread that it gets switched on and off..

Dave

[taylormj4]

Thanks all,
Pump working again now. It must have been dodgy connections at the pump but I was mistaken by thinking that the pump supply would be live all the time the IGN is switched on. I had thought that the pump switched itself off after a couple of seconds by sensing when the fuel line was up to pressure.
Dow! Thanks to all for your help over the weekend. TVR now sat in work car park after a smiley drive to work! Cheers.