It's a 1994 F-250 xlt v8 4x4 with duel tanks.
My problem started a while back when I changed the rear fuel pump, it wasn't exactly the right one, but i got it to fit. When i tried to start it up the fuel pump came on but i wasn't getting fuel to the engine. When i unscrewed the gas cap a lot of pressure was released. So i thought i might have gotten the lines mixed up( old owner had it butchered under there). changed them and then the fuel up won't come on.
So today a finally dropped the tank again and tested the pump to a 12v battery and it worked fine, pumped good.
Used a volt meter on the connection and was getting 3 volts and then 8 volts on another. couldn't test it while trying to start it.
The tank switch on the dash is new, so I know that's good, checked all fuses and relays which looked good.
Front tank hasn't worked since i'v had it and don't want to drop that.

 

The fuel pump is energized for only 1-2 seconds when cycling the key from Off to Run. The voltage you measured is an open circuit. Some will say the voltage is from the fuel pump monitor in the computer.

Jumper Pins 2 & 6 on the data link connector, the one where you plug a code reader in. Then when you cycle the key from Off to Run the fuel pump relay will stay energized.


A photo from Subford:

 

This worked, at first I couldn't tell because I didn't hear the normal kick on sound it makes, but I had the gas cap off and could hear it running, and it was pumping gas with the line off.
So what does this mean? Am I to run it like this?

Thanks

 

Do not run the truck with the jumper installed. You have verified the power path is good to the pump. Now you need to see why the fuel pump relay is not energizing.

The computer applies a ground to the fuel pump relay for 1-2 seconds when cycling the key from Off to Run. Put your meter on the power lead and a good ground. Turn the key to the Run position. Verify power is present. If not, you may have a bad computer.

A diagram from Subford:




If you did get power for 1-2 seconds that means the fuel pump is getting energized as designed. At this point you need to verify what the fuel pressure is. Best way is to leave the jumper in, turn the key to the run position. With a fuel pressure gauge attached you should see 40-45 PSI.

 

Forgive me, I'm not too knowledgeable about this stuff, which is the power lead.
i tested the relay socket while key was on and was getting 12.8 volts.
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Ok so I tried starting the truck with the jump on and was getting fuel to the fuel rail, don't have a fuel pressure gauge so can't tell psi. Wouldn't start though, I don't think I'm getting spark now... How can I test to see if the pcm is bad? I think it might be bad cuz it isn't running the fuel pump like it should, no check engine light, and now isn't getting spark won't even try to start with starter fluid.

 

Pulled the pcm out and found this...

 

Looks like a bad computer to me.

 

swapped out the bad pcm with a used one and truck started up fine, thanks for the help.

 

Thanks for the update. Great!

 

Bump.......