No Volts at fuel pump

[SwankBaton]

Hi,

4L Serpentine, car is totally new to me so finding my way around, mostly off older posts on here so thanks to everyone that has contributed replies in the past.

Car has been stored for a long time, last time it was warmed through it started fine (we are going back a few years though), this time i've got no fuel pump , I'll list what I've observed / tried :

Cranking OK (also Fans / electrics are on)
12v at the Blue FP relay socket
Checked inertia switch under passenger glove box / panel.
Edit - Forgot to add , checked the x2 20A fuses in footwell as well, all fine (alarm went mental after checking the FP fuse?!)

- The above makes me think immob is fine, however i've got no volts at fuel pump at all so rigged a 12v Battery to it and the car started fine.

I've just ordered x2 Bosch 0332014112 relays.

Does this sound like bad relays ?
I did read an older post about the immobiliser can let the car crank / power but have an issue switching the fuel circuit? Or does my observations above sound like the immob. is OK?

Any pointers appreciated, I should probably try jumping the blue socket but might just wait for Relays to arrive.

Also - Are relays a lot more expensive in 2021 compared to the previous posts from a few years back ?

tia
Al

Edited by swankBaton on Saturday 15th May 20:56

[Zener]

Whats missing 12v + or the ground - ? check/probe the multi-plug connector in the B post behind the velcro flapped carpet

[SwankBaton]

Thanks, I had the multi-meter in both spade terminals i was expecting 12v on the circuit, got nothing.

[Loubaruch]

This may help:

http://www.bertram-hill.com/fuel-pump-schematic.ht...

As Zener has said the plug/socket behind the B post is a possibility as damp can corrode the pins. Also the multiway sockets in the footwell.

Edited by Loubaruch on Saturday 15th May 21:56

[Belle427]

As above, be systematic in your testing, start at the relay output and see where your loosing it.

[Zener]

Like I say confirm what you have lost power or ground, anything else is just guessing and wasting time

[blitzracing]

Dont forget to check the inertia switch kills the pump if it gets knocked.

[Steve_D]

Start at the fuel pump relay.
Find a good sound earth for your meters black lead. Leave the relay in place.

Test with ignition off.
pin 30 purple/white has +12v.

Ignition on plus immobiliser disarmed.
Pin 86 white/green has +12v.
Leave ignition on.

The relay has 2 pins 87
Prepare to test the one with a black wire and a white/purple wire.
With the test leads in place turn off the ignition and back on again. You should get +12v for a couple of seconds.

Report your findings.

Steve

[lwt]

Chased something similar (but intermittent) for ages, changed relays, tried the inertia cut out, cleaned contacts etc. turned out to be the immobiliser. I seem to recall tales of factory wiring using the wrong side of the immobiliser relay but may be remembering wrong.
LWT.

[lwt]

Follow up; just remembered that my final proof was not to just look for volts at the fuel pump but to wire in an old headlight bulb to draw current too. Voltage was fine with no load but resistance in the relay contacts meant that the bulb hardly glowed. Hope this helps.
LWT

[SwankBaton]

Update - All sorted, Car sailed through MOT on Saturday , "Clean as a whistle" the tester said.

To close this off, This is what I did :

Went back to the car Thursday last week armed with x2 new relays, did a full lock / unlock on the key fob. Thought I'd give it a try before any changes from previous week and lo and behold the fuel pump worked and car sprung into life!

I've swapped both relays to new Bosch units anyway and will keep the previous x2 as a spare/backup.

Only thing to add is last weekend I did jump the fuel pump on a drill battery and it was fine (car started).

My closing thoughts are that it was the immobiliser playing up, or the relays needed a wiggle - I did pop the negative lead off the battery last week so maybe this reset did the trick (albeit a few days later).

Either way, happy chappy now - its my late fathers car so everyone in the family , including him I bet , is happy its back on the road.

Thanks to everyone who contributed advice to this thread, much appreciated.