fuel tank pressurization

[Posi]

The charcoal canister has nothing to do with how the cap performs.
I would recommend purchasing a new cap chances are the one you have is not the correct one especially if it was random purchase.

Off the top of my head the stant cap part # is 10811, the locking cap is 10592. Double check the numbers on their website or check with your parts guy.

 

[callerys]

I thought it might be the canister might be the issue because the tank does vent to this correct?

 

[Torxhead]

There is a hose going into the charcoal cannister at a location marked "Tank". You should be able to blow into that tube which goes to the fuel tank with the fuel cap off. At this location you could also check vacuum with the fuel cap on to see how good it works, but I do not know how much vacuum it should retain before releasing, if it does. Underneath the cannister is a air filter which should be fairly clean. There is also a couple of check valves inline before the tube from the cannister gets to the tank.

 

[Lumpy Grits]

I thought it might be the canister might be the issue because the tank does vent to this correct?

It does-IF the canister's bottom is pack'd with mud etc it can't 'breathe'.
LG

 

[callerys]

will check that as well this weekend and report back. thanks guys

 

[Lumpy Grits]

Something to think about-
Evaporation Canister
LG

 

[Posi]

I agree with Torx, and LG check the charcoal canister and line for blockage and repair.
However, a blocked canister filter or line to the tank shouldn't cause the symptoms you say your having (gush of air and fuel spitting out) "if" the fuel cap is working as it should.

It would be similar to deleting the charcoal filter and connecting the 2 tank vent tubes together with a hose, if the cap is working it would release pressure. If set up this way chances are you would have a slight raw fuel smell in the morning if you parked your Jeep in a garage, having a properly working charcoal canister will filter the raw fuel smell.

It could simply be a bad pressure valve in your cap or the incorrect cap.

I also believe you have another issue with either your fuel pump, feed line, or fuel pressure regulator in the TB. The late 80s early 90s gm TB vehicles all came from the factory with a 5/16" return line, all howell FI units come with a 5/16" return line as well. Torx runs a 5/16" as I do, there shouldn't be an issue running 5/16" return unless there is a problem elsewhere.

It may have been a kink, or restriction with your original 5/16" line, or your fuel pressure regulator is set too high (located in the TB). Maybe the larger 3/8" return line you installed is dumping more into the tank adding to the higher then normal pressure, could be the larger return line relieved the original problem as well. Just my 2 cents