Quote:
Originally Posted by SoCalSlaughter
Ive checked and rechecked all grounds in the cab, frame and motor and all are good. ...
|
How about the ground wire to the fuel tank sending unit?
Quote:
Originally Posted by SoCalSlaughter
... Hooked up a 12v current to the fuel pump and it will run, but the truck will not make it run. Tested voltage on fuel pump wires and getting 8.45v with key on.
|
What voltage, on what color wire?
One wire should be a ground and have no voltage.
One wire is for the gauge.
One wire is for the fuel pump and should get battery voltage, but only during the prime cylce that lasts a couple seconds.
The truck has a fuel pump relay that supplies power to the fuel pump when:
- Anytime the ECM receives a distributor reference pulse. (Engine running / engine cranking)
- The key is turned on engine not cranking – relay applied for 2 to 20 seconds (most trucks 2 seconds), depending on emissions equipment. Trucks over 8500 GVW and some other vehicles have and electronic Fuel timer module that allows the pump to run up to 20 seconds.
The key must be turned off for a certain amount of time before it will prime the system again when turned back on.
There will only be power to the fuel pump for a few seconds when you first turn the key to the on position. If you are turning the key on then walking around the vehicle testing for voltage to the fuel pump circuit there will be no voltage and should not be power to the pump.