Is there a way to diagnose if the charcoal canister behind the rear drivers wheel is bad before replacing it. I am intermittently getting a fuel leak by the canister purge valve above the differential and think I might have a bad canister. It sometimes occurs after filling the tank - I don't overfill.

 

Yes, diagnosis is simple. The EVAP line that goes to the canister connects to the fuel pump module, next to the pressure and return lines. There are two ways the canister can get raw fuel in it: #1 is by transposing the fuel return line and the EVAP line at the fuel pump module. If it only leaks fuel intermittently, that is not the problem. #2 is by over filling the tank, which forces raw fuel into the EVAP line, and into the canister.


The canister is designed to capture fuel vapors in the fuel tank, (on top of the fuel) and store them. If/when the canister is exposed to raw fuel, it must be replaced, the damage is done.

 

Thank you for the quick reply. You confirmed what I was thinking. I will replace the canister since fuel has flowed through it.