Fuel Pump Relay Control

I've had an intermittant problem with my fuel pump over the last year or so on my Black Rat Campaign.

Very occasionally the fuel pump just will not run.  When I have this problem I have inserted a manual switch on the fuel pump relay fuse box contacts and operate the pump manually.  Car runs fine.

By the time I get round to looking at it - I'll bung the relay back in and it'll work fine.

This time I've managed to look at it when I have the fault!

Things i know:

Not a pump pr pump wiring problem

So must be a relay or relay control problem.

I have tried another relay in the past but it did not solve the problem, so I went down a relay control problem route…..

On the Fuse box there are three connections:

15 - Connected to one side of the coil
31 - Switched 12v from ignition switch
31b - Connected to the other side of the coil

I've measured voltage in three states:

Ignition off:
15 - 0v
31 - 0v
31b - 0v

Ignition on:
15 - 12v
31 - 0v
31b - 12v

Engine cranking:
15 - 6 to 12v
31 - 0v
31b - 12v

This all seems fine.  Double checked voltages on the Silver Campaign and all were the same so I did a bit of head scratching.  I know the Silver Campaign starts on the button - tried starting it today after 2 or 3 weeks and it fired on the first flick and settled to a nice tick over within a second or so.  The relay must be good.  Tried it in the black one and hey presto fires up straight away.

I think the thing that gave it away is that with the Silver Campaign and the cab you can hear the fuel pump buzz for about 2 secs before cranking the engine.  I don't think the black one has ever done that!

So problem sorted after months, ney years of messing about all cos i tried aonther relay and that must've been bad also    

Cool… glad you solved it!

when I try starting mine the fuel pump doesn't start for a good few seconds of turning over (think the inlet manifold gasket is part of the non-idle problem i've got so got a new one to put on)

think I should replace the relay as well?

also on the subject, does the fuel pump stop pumping once it's up to pressure? or am I talking nonsense?  

While the engine is running, the fuel pump runs constantly...

had better get it to idle then check if the pumps doing it's job really then  :wink:

Yeah if the engine is running fuel pump should run also.  You can bypass the relay usinga switch and some wire as shown in prowler's fuel pump test.