Smelly EVAP System, Charcoal Canister, How Does It Work?

[Black1990jeep]

On a 1990 XJ six cylinder Renix I once and a while get a whiff of gas smell, smell it when working under jeep. jeep has not been driven for five weeks. I suspect the smell happens do to the EVAP system charcoal can, or its hoses or?

I have the factory service manual, but it is not detailed on the EVAP system.

my charcoal can has two hoses up top, one to the air intake boot, the other goes back to the gas tank. On the bottom of the charcoal can is drain hose that is open on the end facing down at the road.

The smell seems to burp every now and then, it is a fleeting smell

At the gas tank At the vent hose is there supposed to be any valve, check valve, a roll over valve or such, or does it free vent to the top of tank?

What might cause my charocal can to become smelly? to burp (the burps might corrolate to the temperature warming at mid day)

What is the purpose of the drain tube on bottom of the charcoal can?

PS, I wheel at sometimes extreme angles, and have over filled tank many times to squeeze extra range in. Could either have flooded the charcoal can?

Thanks!

 

[Saudade]

It's not a drain, it's a fresh air inlet. The FSM is not very detailed because the evap system is pretty simple.

There's a venturi in the air cleaner tube that creates a small vacuum. This draws the vapors from the canister when the engine is running. The other port on the canister is a metered orifice that connects to the fuel tank, the source of the vapors. The bottom vent allows fresh air to be drawn in and mixed the the fuel vapors. Ultimately, it's all drawn into the engine for combustion.

So check for any cracks in the canister, the lines from the tank and to the air cleaner. Pull the air cleaner tube (snorkel) off and check the venturi. It's certainly possible that extreme angles and overfilling could back some extra fuel up the lines. This could make the fumes escape the canister if it sits for a few weeks. After all, the canister is pretty old.

Your '90 should have a rollover/relief valve but I don't think it's connected to the evap.

 

[GravyDavey]

I believe there's two rollover valves on the top of the gas tank which vent the fumes to the charcoal cannister. I have heard that overfilling your tank could result in a flooded charcoal cannister.

The smell is mostly from the front of the vehicle, not the back?

I had a few evap leaks that needed to be fixed when I got my jeep, both front and back.

 

[Black1990jeep]

Yes smell is from the canister, the drain hose specifically. It comes and goes, usually burps fumes as the day heats up.

I need to address this as in the next few days I will be welding center frame stiffeners on the jeep. Gas fumes frighten me if welding.