I have a 1988 F150 V8 5.0, 2WD. I have two tanks front and back I have the same problem regardless of which tank I use. The truck was running fine up until about a month ago. It would run anywhere from 2 to 5 miles then suddenly shut off, acting like it was out of gas, every time this would happen I would have approximately a half tank of gas in the front tank. I could try to crank it, 3 to 4 times it would turn over but never actually crank, next try it would crank and run for 2 to 5 miles and repeat. It did this for about two weeks, and then I shut off and would not crank again. Thinking I may have air in the fuel line I bled the line, and could not get any gas to come through. I then check to see if my fuel pump was turning on, it was not, the two relay under the hood for the fuel pump and ecc were clicking. So I dropped the front tank to replace the fuel pump, tested the pump once I got it out of the tank and it works properly. I the test the power line feeding in to the pump and I only get a charge of 8.4 volts coming through. The strange this is that if I pull out the two relay I still get an 8.4 volt constant charge. Does anyone have any idea as to what the problem may be?

Thanks,
Mike

 

Is the frame pump working? You have three fuel pumps and if the frame one isn't working neither tank will work.

 

I haven't checked the frame pump, if it is not working would that cause the wrong voltage to be sent to the tank pumps? Also I'm at work at the moment I'll check the frame pump when I get off.

 

If it's seized it could be drawing most of the voltage.

 

Ok, tested the power line running in to the frame pump, it's only getting 6 volts, with the frame pump power disconnected, the pump in the tank is not getting any power. Which leads me to believe I got a wiring issue somewhere and not a bad pump. But I could be wrong.

 

Hotwire the pump. See what happens.

 

I found the problem(s). I took a close inspection of the wiring harness, and found that the guy I recently bought the truck from had very poorly rigged the harness up and everything is shorting out. The harness is so messed up that if the ignition is on and if I grab the harness in a certain part the engine will turn over. Thank you for your help.