I feel like I knew how to do this years ago but now I can't figure it out. I need to cut power to fuel pump for tuning purposes so that the pump doesn't build a bunch of pressure on lines while car is off but with ignition on. I know I can take off the engine fuse and that cuts power to it but then I can't tune properly. How can I do this without just disconnecting the pump? Any ideas? Thanks

 

i unplug the circuit opening relay, on an LHD car its right above the drivers right knee, so you can reach it from the drivers seat.

 

I actually have a switch on mine. The weather and my work schedule are not conducive to taking photos of it right now, but maybe tomorrow if you can wait.

 

Thanks guys Ill look into the relay today. Ive thought about just putting a switch for this I just hate messing with electrical stuff on this car.

 

another thing you can do is disconnect the fuel pump at the pump.
the connector is a little hard to get at but it will work for what you want to do.

 

Why do you need to cut power to the pump for tuning purposes? Not build a bunch of pressure? Unless you have some weird rail setup, the fuel pressure is set by the regulator.

Or unless perhaps you have WAY to much fuel pump for a carburetor and the wrong regulator?

Also the fuel pump should NOT run with the car powered up unless the engine is running. Any EFI system will have a fuel pump output that cuts if the ECU doesn't see RPM.

If you have some sort of carb conversion, then it's a different story. But in that case the fuel pump should be relay controlled with a rollover switch anyway, so just trip the switch or disconnect the relay.