I have a 1994 4.9 f-150 with Duel tanks. When I bought the truck both tanks worked fine. I as I fueled up I would switch them back and forth to keep the fuel clean and fresh. A month or so ago, the front tank stopped working. Being busy I just used the rear tank. Then it started acting up. When I would start the truck I would sometimes have to switch it to the front tank then back to the rear tank. Then it would start and run. Went out last night and nothing. No matter how many times I switched it it would start. The fuel gauge works on both tanks. Just doesn't pump any fuel.
Anyone know what it is?

Stranded.

Jeff

 

It sounds like an issue with the selector switch.

When you turn the key from "off" to"'run" (not to "start") can you hear the pump running for a couple of seconds? Can you hear it on either tank?

 

O.K. we have tried your suggestion. After flipping the switch a few times the rear tank came back online. The front tank however has not. Any suggestion?

 

O.K. we have tried your suggestion. After flipping the switch a few times the rear tank came back online. The front tank however has not. Any suggestion?

 

If you can't hear the front pump make any noise when you turn the key to the "on" position and the rear one is still working i'd say the front pump is burned out.

 

That does not explain the intermittent issue with the rear tank.
For something to be going wrong on both tanks it has to be either the fuel pump relay or the selector switch. Relays don't tend to give intermittent failures; they either work or they don't. That makes me think the switch is the culprit.

...and the front pump could very well be burned out as well.

 

Test the parts with a volt meter before you start replacing. There are too many expensive parts to just start replacing them without testing first.

 

O.K. Thank you all for the suggestions. I did replace the selector switch. No more problems with the rear tank. Still no front tank, but no more problems with the rear tank. So now I have to assume the pump is bad. But before I take the time and effort and considerable cost to remove and replace this pump. Is there a places without dropping the tank, to make sure the pump is getting power?

 

There is no component between the fuel pump selector switch and the pumps. However, they do pass through a multi-pin connector on the firewall so you could probe the circuit there. Since your truck is a 94, I cannot give you the pinouts or wire colors since they are very likely different from my OBD-II/MAF 96.