hi guys,
installed a walbro 255l/h fuel pump yesterday, was reading up about fuel pump rewire also. checked the voltage at the wires at my pump at idle i was getting 8volts. is this low?
even when cruising voltage would only increse to about 9-9.5v after letting off the accelerator....
when i run the microtech in a about a week, will it still be necessary to do a rewire as i have the positive wire from the microtech relay spliced into the 12v wire at the pump.

thanks
Andrew

 

When you wire up the MT you should run a new heavy-gauge wire to the fuel pump, wired up as per the MT wiring diagram. Don't worry about the normal rewire, that only applies when using the stock ECU.

 

hi jason,
i plugged my microtech in (piggy backed into factory loom) and checked the voltage at idle with headlights on. Readings were at fuel pump wires.
blue wire: 14v
black/white: 12v
Red: 4v

i have the lt8 relay wire running to the back of the car spliced into the blue wire. i did have it hooked into the black/white wire but car wouldnt switch off when key turned off.

do these figures sound ok? i did drive the car with the voltmeter hooked up to the wires and there was no difference in voltage.

what sort of voltage does the walbro 255l/h require to pump the required fuel (if u know of the top of your head, if not dont worry about it ) i have been told on ausrotary.com that the stand fuel pump wiring does not supply enough voltage to properly power the walbro pump i am running.

Thanks
Andrew

 

The blue wire is the pump power wire, so 14V is good. The black wire is the ground wire and the other two are for the fuel gauge and low fuel warning light.

The Walbro does draw a lot more current than the stock pump. According to this page the 255 draws up to 17A @ 13.5V, which is probably double what the stock pump draws. That's at dead-head pressure though; realistically you'd probably see a 11-12A draw. I would upgrade both the ground and power wires right up to the pump if you can. I used 12GA wire when I rewired my pump.