'86 CRX burps fuel out the filler

[Petros]

I thought some of you might know the answer to this problem my daughter's CRX. Sometimes when the tank is filled it burps fuel out the filler after a few min of driving. I suspect something is wrong with the carbon canister/fuel cap venting. When the fuel warms up, instead of venting air out the canister it burps out the filler, making the car smell like gas and damages the paint below the filler.

I had a spare fuel cap (used) and carbon cansiter (also used) from the parts car and I swapped them out. I do not know if it fixed it yet.

Is there anything else that might cause this? It is the carburated CVCC engine (not EFI). I think our Tercel uses the same kind of system.

Thanks for any ideas.

[danzo]

Did you notice if the muffler heat shield is intact? Years ago an old Datsun Z car buddy of mine had an aftermarket exhaust with the heat shield removed. It was really impressive how much fuel would boil out the filler after a few minutes of running. Otherwise I would suggest tracing the vent lines and making sure they aren't clogged. Just trying to brainstorm here. Good luck and let us know what happens.

[4wdchico]

Locate the vapor line from the tank to the carbon canister. Remove this line from the canister and check that air flows freely towards the carbon canister. Please devise a safe way of doing this w/o inhaling gas fumes... Here in Calif. when a cars evap system is tested for leakage 1.5 psi of pressure is applied to a special cap on the filler neck. So if you decide to go this route, not exceeding this pressure might be wise.

If this flow is not present, a look at the FSM would be a good idea to get a picture of the vent system at the tank. Some Asian cars have somewhat complicated fuel/vapor separators and the like near the fuel tank. I have seen a 'yota that burped like you are describing when the fuel return line on the bottom of the fuel/vapor separator got a pinch in it.

[takza]

If the gas cap was good...fuel wouldn't get out?

[Neu]

No fuel caps will leak, they dont make a very great seal.

[Ron B.]

No fuel caps will leak, they dont make a very great seal.

And you know this how? Would you like me to show you a cap that leaks?

[toughtercel]

few months ago ,when I unsrewing the fuel cap it make a loud "shhhhhhhh" sound for 3 second then tested again next day same thing so I replace the fuel cap it stop making noise , old cars has vent tube connected to top of fuel tank ,vented higher than fuel filler neck .

[takza]

Mine holds pressure and goes shhhhh most of the time. They are supposed to have relief valves both ways in order to not overpressurize the tank or allow it to collapse.