1994 F150 5.0 supercab 4X2 XLT automatic trans dual tanks

I believe the rear fuel pump has gone bad. I’m trying to get some straight answers. Anyway truck runs just fine on the front tank. Flip switch to the rear and it dies. Set switch to front tank you can hear the pump prime truck cranks and starts. Set switch to rear tank you do not hear the pump prime it will crank but will not fire.

I’ve been told that this truck has 3 fuel pumps. A low pressure in each tank and a high pressure to the Injectors. I’ve also been told that that’s not true on these trucks. They have a pump in each tank and both are high pressure. How do I verify which setup this truck has? Is their and easy way to tell?

I bought the truck used and the rear tank did not work. I checked all the fuses for the truck every fuse is functioning. I found a couple fuses were the improper amperage. So I swapped them to correct fuses.

I turned on the key switched to rear tank, separated the rear fuel pump jumper or whatever it’s called and check the voltage with a multimeter. I believe the sending unit was showing 8.33v and the fuel pump was showing 10.00v. The battery voltage was 12.39 with the key on ect. I had also had it on for a while while messing with it. Is 10v to low for the pump. Also 2.39v drop seems like a lot to me it’s a 20% drop in voltage. Obviously this is not the voltage while the engine is running.

if 10v should run the pump is that much of a voltage drop indicative of another problem arising? Trying to make sure I rule out any other possible issues before replacing the pump. Also trying to see if this could be an indication of another problem creeping up.

Thanks.

 

No, you only have 2 pumps, one in each tank. The older trucks (pre-1990) had the setup you describe.

 

Thanks. That’s what I was hoping.

 

You may have a bad check valve or shuttle valve in your front tank.
You need to check the fuel pressure with a gauge from each selected tank with pin #6 of the self-test connector grounded and the key in the run position.