The vehicle is a 2003 Ford E-250 with a 5.4L 2V V8 gas engine. When this code was set, I noticed a hiss/fart/burp when removing the gas cap.

I know what the code means, and I have the FSM DVD. Since the Evap system is a sealed system, I don't see how debris, mud, spiders, dirt, asphalt can get into the hoses. I've checked for kinked hoses, vacuum leaks, etc... to no avail.

I removed the canister and cleaned out the canister vent solenoid with brake cleaner and replaced it. I reset the DTC code and all was "well" for a week or more. I can still hear a hiss/burp/fart when removing the gas cap at the gas station but no DTC code has been set.

I read that a stuck closed canister vent solenoid (9F945) can set this code, or a stuck open canister purge valve (some people are calling it a management valve... but the catalog says purge valve, 9C915).

The difference here is that I can hear an audible noise when removing the gas cap. I've tried 2 different caps, the OEM Ford cap, and a Ford locking gas cap for a 2000 Crown Vic. I checked the cap specs on the FSM, and the E-250 has the same specs (max/min pressure, vacuum relief, etc...) as the Crown Vic.

When I applied +12V to the canister vent solenoid, I did not see the valve close or open. I did hear it go "PLOP" whenever it was energized.

Has anyone successfully solved this problem?