My '91 F-150 with the 4.9 overflows its rear tank when I use the front tank. I understand that this is a pretty common problem. It's also my understanding that the dual tank setup may be a bit different between the 8th and 9th gen trucks.

It sounds like there was a recall specifically for this: https://www.ford-trucks.com/forums/1...tml#post989117

I called and there's no record of the recall for my truck. Assuming I won't get a free pass on this one. Sure would be nice to have a dealer take care of it for free!

Do I need to replace the rear fuel pump to fix this? Or just a check valve? I guess there might be a few possible causes. It's my understanding that I'll need to pull the bed to get access. Are reputable pumps available? Not sure if this is a Rockauto deal, or if I need to look on Ebay for NOS Motorcraft.

Also, when running with the rear tank, the truck doesn't run as well. Especially when just starting it, it tends to not take throttle for a little while. Maybe the fuel pump sock is clogged?

Thank you!

 

The parts to do the recall have been obsolete for years
That said, the recall parts fix them all (I put one on my last 04 F150)
A failed one way valve in the fuel pump is the problem and the recall one way valves were a band-aid
These are them if you happen to find some on a junkyard truck, get them
They made long and short ones
The long ones are for the metal lines