the gas tank vent line that runs from the tank to the "tank vent valve" by the charcoal canister is plugged somehow. I tried blowing it clear with compressed air, but no go. any one have any suggestions?? I COULD make another one. but I don't wanna! this is probably why my tank builds up so much pressure on a hot day, come to think of it.

 

If you can't blow air back through the steel line, with the gas cap off, then there is a restriction. Could be as simple as a rubber hose at the tank being pinched ( done any work there lately?). Could also be accumulated rust in the steel line blocking it off.

A simple fix is to run 5/16 rubber fuel hose back to the tank. Since it only carries fumes, and then only at 2 psi, regular hose will work fine. This is how I plumbed my conversion.

However, if the vent tube at the sender is plugged, this won't help.

 

yeah, that's probably what ill end up doing to it.i haven't got it up on a lift yet to inspect. but im hoping it will be a easy one.

 

The sending unit has a small orifice (restriction) along with a rollover valve (caged steel ball). It is also possible that the vent line is smashed someplace along the way from the front to the rear.

Disconnect the rubber vent line at the tank. Then see if you can blow compressed air from that point to the front, or from the front to that point. That will let you know if the steel line that runs the length of the car is OK.

If it is, then try compressed air at the vent line at the tank and verify that yes, the sending unit is plugged. If so I'd try up to 30 psi of air pressure to see if that clears it. If it does, then spray some solvent in the vent line back into the tank. Followed up by some air.

The worst case is that the rollover valve is rusted up. If so then a new sender may be the only way.

RBob.

 

thanks rbob, this is what im gonna do. obviously ,replacing the tank sending unit would be the worst case scenario!!