fuel tank check valve

[officalfordtow]

was wondering if the check valve on top of the fuel tank, that is routed to the vapor cannister, would be the cause of failing a evaporative smog test, in cali, if the valve is faulty.

[PEZi]

This is why I hate Cali. I suppose it is possible. What exactly are they testing for in the "evaporative smog test"???? I have a hard time believing a system so useless and minute is causing a fail... but I dunno for sure.

Is the breather line clean and the line from the evap canister to the engine clean?

[officalfordtow]

yes did a vacuum test, with other end plugged,ckd good, from the tank it runs along rt frame, then branches to frt diff, trannie, before going to the vapor cannister, and ck good from cannister to engine. I have factory manual, i know this truck inside n out over the years, but still on a learning curve, lol

[PEZi]

I guess the check valve could cause this. My bet is on something weirder, though. EGR.