Folks, I know this issue has probably been answered many times, but I haven't mastered the search function yet so please bear with me.

I have a 1994 F-150 XL 4.9 Straight six automatic w/OD transmission and A/C

Here's the problem. Only my front tank works.
Symptoms:

1) If I switch from front to rear on the dash switch with the key on, the fuel gauge shows the correct level in each tank. (sending units good? Dash switch good?)

2) The truck will start and run normally on the front tank.

3) If I switch to the rear tank as the truck is running, the truck will sputter and die, but I have just enough time to switch back to the front tank.

4) The truck will not start at all with the rear tank selected.

I have no crossover between tanks. Fuel in the front stays in the front and fuel in the rear stayed in the rear until I needed gas and had no money. Everything they say about bad or old gas is true, btw.

So, I've looked at manuals and searched Google and I supposed the Fuel Module in the rear tank is at fault, but I can't figure out if I have a switch on my frame rail as well that may be faulty. I'm not sure where my truck falls in "Early EFI" vs "Late EFI".

Any advice would be appreciated. I bought this truck with the last of my dear Mama's left over insurance money so I call it "Mama's Last Gift" and I just want to get things right on it.

Thank you all.

 

I'd say the rear pump is bad. If you are able, remove it first before you buy a new one to match it up. When I did my front, there were several different ones with no way to tell which one I really needed. Short bed, long bed, plastic tank, I don't remember what all the variables were.

 

each tank

has its own style pump.

 

As stated you have a bad fuel pump inside the rear tank module.
No you do not have any switch or anything on the frame rail other than a fuel filter.
Yes it could still be the selector switch on the dash as the fuel pump contacts in the switch have nothing to do with the gauge contacts.
A bad fuel selector switch:








/

 

Very good info above from subford. I have the exact same truck and have been thru several pumps front and rear. Can just about guarantee from my expreince the rear pump is bad.

 

Wow timely posting of this thread I'm replacing my rear pump this weekend. I'm removing the bed to get to it though to also check for shorts as my fuel gauge isn't working as well.

 

Hi, was this resolved by replacing the sending unit/pump in the tank?

I have the exact same problem on my front tank. I just replaced the tank too and put it back up so have to drop it again.

The truck sputtered and died and I switched to rear. When I got out i noticed the front tank was leaking so maybe thought the release of pressure was why i couldnt have it selected while the truck was running. Think its just a coincidence that the pump gave out and it leaked at the same time.

These things are between $250 and $300. Has anyone tried to fix one instead of buying a new one? Which part on the thing fails?

 

I have read about a few on here that seemed to stop pumping and start fuel transfer at the same time for some reason.

 

So while my front pump is busted can i still run off the rear tank or does the rear tank pump gas into the front tank which will just end up filling up since the pump is dead and ultimately drain the rear? This is a 96 F250 5.8

 

I do not know if your front FDM is letting fuel in but if it is not then yes you can run off the back one.
Sorry my crystal ball is a little foggy today so I can not see into your fuel tank.

 

What is FDM?

Do the dual tanks in the 96 usually operate separate or does the fuel from one tank run through the other and pump back into the other tank?

How can I determine?

thanks

 

Fuel Delivery Module.
Look at post #4 above.

They operate separate. Look at post #4 above.


Determine what?