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I have a 1994 f150 with a 4.9 in it. Recently when driving the truck it will randomly sputter hard and act like it's not receiving any fuel. After I'm done driving both fuel tanks will have enough pressure in the tank to push gas out of the cap if you open the cap just a hair. I've recently had the fuel pumps replaced and the issue wasn't there before the replacement. Do I have two faulty fuel pumps?
I would definitely talk to whoever did the fuel pump replacement.
Your fuel pumps should have a built in check valve to prevent cross filling.
Another possibility is that the EVAP system is damaged or not intact.
Here are pictures of the EVAP lines from my '88.
The EVAP system vents fuel vapors to a charcoal canister in the engine compartment, which then is vented into the intake via a solenoid.
Drive the truck around with a fuel pressure gauge taped to the windshield
Your rollover vent valve is no good if it will not vent the tank
It might just be stuck
Remove that vent valve and smack it around some, see if you can get it to flow air out the tube
Your rollover vent valve is no good if it will not vent the tank
It might just be stuck
Remove that vent valve and smack it around some, see if you can get it to flow air out the tube
…or the hose got pinched when the tank was reinstalled.
