Losing fuel pressure

[Twisted_Steel]

Each of the last few times fueling up my truck I had ALOT of back pressure when I removed the vent cap. Each time I release the cap and fuel up, I go about a half mile and the truck shuts down as if my fuel pump shut off.
I can hear the pump running louder as if it has lost prime. After she sits about 10-15 minutes I can hear the pump prime and I'm good to go.
I'm leaning toward either the vent tube is clogged or obstructed in some way or maybe the evap canister is clogged.
It's not an electrical issue because the pump continues to run and this only happens after the pressure is released from the tank. (Positive pressure.. not vacuum)

Any Ideas other than that?

 

[adsm08]

If you can fill it normally it isn't the vent tube.


I think I would suspect an issue with the pump itself, but that is just a guess.

 

[RonD]

The vent tube runs next to the filler tube, it is just for filling the tank with fuel, allows the air out as fuel goes in.

Yes, fuel pump should have a check valve that prevents fuel from draining back into the tank when engine is off, that check valve maintains the 30psi fuel pressure at the rail along with the Fuel pressure regulator(FPR) located on the return line on the rail.

If the check valve isn't working then when you release the tanks positive pressure by removing the gas cap, the fuel in the rail can drain back, lowering pressure in the rail, causing a stall out after start up.
Same type of thing could happen if the FPR was leaking pressure.

Positive pressure in the tank can come from warm weather, not sure if the '91 Ranger tank used a high pressure vent cap or not.

But the EVAP system should be sucking out some of that pressure, via engine vacuum so yes, maybe you have a stuck EVAP solenoid or clogged canister, both are pretty easy to check.

 

[Andy D]

Next time it happens, open the gas cap

 

[kunar]

Next time it happens, open the gas cap

that's exactly what i was thinking. is the fuel pump pulling a vacuum on the tank when it's full and there's a small amount of airspace?

had something similar happen with a lawnmower once. older guy had lost the gas cap and just grabbed some random plastic cap that fit. it sealed off the tank when it should have been vented. it would only run for a few minutes then stall.