Getting ready to wire my new guages up and wanted to know how many wires on the back of the Fuel Pressure Guage so I can plan for it in the harness I'm putting together. I don't have the guage but I figured I would go ahead and run the wires for it while I'm at it, so I won't have to go back and do it later.

 

I don't know what kind of gauges you are using but the Autometer guages use 3.
1: Ignition
2: Ground
3: Sender
The Autometer senders have a ground terminal built into them so one wire to your ignition and the other two to where your sender will be.

 

My DynoTune gauge has four wires so that the sending unit does not have to be grounded to work.

1.) Switched 12 volt power source.
2.) Ground
3.) Power wire to F/P sending unit.
4.) Ground wire to F/P sending unit.

Wires 1 & 2 are run in the cab and 3 & 4 are run through the firewall to the sending unit under the hood.

 

Thanks, the Autometer is the one I plan to use. What about lighting, same as my trans temp with just a hot and ground wire?

 

If it is digital, it needs to have power WHILE the engine is cranking for the calibration of the gauge.