Fuel pump relay on EFI

[paulmmc]

Hi,

The purple/white lead coming out of the fuel pump relay (next to the ECU under the drivers seat) does not seem to be passing voltage throught it. There is a good 12v into the relay, and it clicks when power is supplied but only seems to pass about 0.5v out to the fuel pump. As such i am running the fuel pump direct from the ignition points to supply power when the key is turned, will this eventually break the pump if it is running full time?
And if the pump is wired up separately does that mean that the ECU will not tell the fuel pump to fire?

Any help greatly appreciated?

Paul

[hairyasswelder]

If its a flapper system the air flow meter tells the pump to run. when it first opens it makes contact.
The 3.9 is a little more complcated.

Steve

[paulmmc]

It is the flapper type. So does that mean if i wedge the flap open for the purpose of testing the pump should run full time?

[hairyasswelder]

Mine does, I had a starting problem and this was the cause.  If you prop it open, then open the fuel filler you can hear the pump running  ;) the pump runs full time with unused fuel going back to the tank.

Obviously when you turn off the flapper goes back to its rest position and turns the pump off.  Also had trouble this way round due to LPG backfire  :(

[paulmmc]

Right, over the weekend i tested the power supply lead (white/purple) coming out of the fuel pump relay with the voltmeter and even with the flapper propped fully open no voltage is passing through the cable. There is 12v going into the relay.
Any one got any suggestions what could be wrong, and if not shall i just leave the pump to run full time while the key is turned to the second stop in the ignition.
I don't see a problem with this so long as i dont always leave the key turned to the second stop unless the engine is running or am i missing something?
I would rather it works properly though.

Cheers,

Paul

[Rossko]

Right, over the weekend i tested the power supply lead (white/purple) coming out of the fuel pump relay with the voltmeter and even with the flapper propped fully open no voltage is passing through the cable. There is 12v going into the relay.

You could investigate if the control signal gets to the relay - which I think is white/green going to 12V with flap opened.  If it does, pump relay is goosed.
If that doesn't happen, go back to previous unit - the diode pack that looks like a relay.  Blue/purple should go to 12V when flap opened.  If it does - diode pack is goosed.  If it doesn't - AFM contacts are goosed.
Useful diagram
http://www.spagweb.com/v8mini/tech_files/efi2_diagram.jpg

if not shall i just leave the pump to run full time while the key is turned to the second stop in the ignition.
I don't see a problem with this so long as i dont always leave the key turned to the second stop unless the engine is running or am i missing something?

Safety compromise.  In the event of an accident severing the fuel line, the original design stops the pump emptying the complete tank over the hot exhaust, for the comfort and convenience of occupants.