Engine/Transmission (1994 - 1998) Pressure at fuel cap

[dodgeguy44]

Should there be pressure at the fuel cap at all times or is there a problem in the fuel system?

 

[LPittsley]

I don't know if you should have pressure or not, I do. When I shut my truck down and get out of the truck I hear a high pitch whine. After years of not knowing. I ordered this truck in 1994 and figured it out last year. I let the pressure off of the fuel cap and the whine quit. I don't tighten the fuel cap very tight also. Hopefully that will help.

 

[CStansbury]

Mine has pressure at it when I open it to fill up. There is a warning on the cap about it so I figure it is normal. I figure the fuel is cold when it comes out of the ground and then it warms up some in the truck increasing the volume and displacing some air.

 

[NHays]

Bad fuel Cap

The fuel cap should have a valve in it. I had the same problem. No, the fuel tank should not have a substantial amount in pressure in it. Get a new fuel cap or take a punch or pocket knife and destroy the little spring valve assembly on the bottom of fuel cap. You will see what I mean.

 

[Nate]

Yeah sometimes when I go fill up and I spin the cap off quickly it "whooshes"

 

[dodgeguy44]

The fuel cap should have a valve in it. I had the same problem. No, the fuel tank should not have a substantial amount in pressure in it. Get a new fuel cap or take a punch or pocket knife and destroy the little spring valve assembly on the bottom of fuel cap. You will see what I mean.

I thought the fuel cap should be vented, my 94 was. I'll make sure it is vented now. Thanks

 

[TPCDrafting]

There is a vent on top of the fuel tank, where the round cap is with the fuel lines coming out. The vent comes out and 90's, then terminates. The hole is plugged with dirt/debris if your tank is sucking air when you open the cap. The little vent tube dia. is perfect size for those little red spray can tubes. I squirted a little brake clean into mine and the sucking air stopped. There have been pictures posted here showing tanks getting sucked in from not enough venting.

 

[CStansbury]

Yeah sometimes when I go fill up and I spin the cap off quickly it "whooshes"

Yep, mine is just a quick "whoosh" too, no suction, just a little blow