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There are a few elements in the fuel pump circuit:

1. ECM B fuse
2. Fuel pump relay
3. Oil pressure switch
4. Energizing circuit for the relay
5. Wiring, power and grounds

First check the ECM B fuse. Then jump the fuel pump and start the truck and see if it stays running after you remove jumper power. That will tell us if the oil pressure switch circuit is working.

George

 

Hello again, thank you for your help, I tested the voltage to my fuel pump plug, and when I turn the key to the on position it only gets 6.95 volts? , and the pump does not come on, I've checked the relays and fuses, there good, so what could be causing a low voltage to the pump and is this why it's not coming on??? How would I go about fixing this issue, your help is greatly appreciated. Thank you.

 

1. When you measured the pump voltage at key on where did you attach the 2 meter probes?
2. Do the test again at the priming tab in the fuse box using battery post ground.

George

 

Hello, thanks for your reply, I test the power at the plug, the purple and black wire, purple being the hot side and black, ground, I will try at the fuse box like you said, but I think I found the issue to the low voltage!!!!! I pulled my battery out to charge it, I then remembered the main positive wire goes under the battery box, and there is a fuse junction box,,well it was uncovered at touching the inner metal fender well, so it basically was shorting out the main power!!! So I now think I found the issue to why I was only getting 6 volts to the pump, I will clean those connections up and make sure the sealed and even wrap electrical tape around that plastic box, so it don't become exposed again., then I will check the pump.again and see if it comes on !!! Wish me luck!!! Thanks again!!!! I'll always now remember, start from the battery and check all wiring and connections!!!

 

Purple and black is the fuel gauge sending circuit, not the fuel pump. You want gray (A) and black (C). If your main battery cable had really shorted to the truck frame you would get a spectacular 200 amp fireworks show and potentially a fire or exploded battery unless it was after the mega fuse in which case the fuse would blow.

George

 

Thanks again, only the hot wire, (red) was touching the fender well, were that fuse was, it was touching, I guess causing a draw or voltage drain, I fixed it, it didn't spark or catch fire, thankfully. I have a new battery in, cleaned all the wire connections, even the grounds, but I still have no fuel pump working when I turn the key forward, could it have anything to do with the ignition switch? the fuel pump.was working before, and it doesn't now, I already checked the relay, but you ask for me to check the voltage at the primer port and or were the relay goes?

 

You were measuring the fuel gauge sender circuit at the tank on purple and black. You need to repeat that measurement on gray, pin A and black pin C (there are two blacks) to see if you have proper voltage at the fuel pump at key on.

George

 

Thanks, I'll check those wire for voltage with key on, the only thing is when I run a.jumper wire were the fuel pump fuse is located, I can hear the pump run, so how can I get the pump to work with the key on? Or is the pump possibly fualty?

 

So will the truck start using the ignition switch to start when you jump the fuel pump power at the fuse box?

Remove the jumper and measure the voltage on that priming tab with all fuses and relay in place at key on.

George