P0442 on 2004 Tundra

This is a small leak in the evap system. I replaced the gas cap and filler neck a little over a year ago and the code cleared but came back on a few months later. This is not my primary vehicle but I need to get this fixed for a state inspection. Truck has about 230K miles.

I tested purge valve under hood and it appears to pass a vacuum. There is a small loss of vacuum but I attribute that to my ability to make a good seal. Maybe I'm wrong.

There is another valve near the charcoal canister which I took off and stimulated with current and it appears to operate.

I built the YouTube smoker and smoked the system. I observed smoke pouring out of the fuel port. I replaced the gas cap with an after market cap from Auto Zone. and smoked again.

There is smoke coming out but it appears to be on the inside of the filler neck assembly around the plastic collar. I took the filler neck off. There are three tubes: Main gasoline tube, small 1/8" opening tube, and a 1/2" tube. When I blow in the gas tube and seal the 1/8" tube, no air comes through. When I blow in the 1/2" tube air escapes around the plastic cowell. Is this by design? Is that a breather tube. Is this why I have smoke coming through? Should I have key on/engine off when I smoke? Would that close a valve that would prevent smoke from going to this tube?

Or, should it not be allowing air to pass and it's just broken.

New to forum. Sorry for the first post being so lengthily.

 

Just push on your gas cap as you are tightening it. I changed both the same parts and I always get that code after gassing up if I don't push.

 

you need to use a scanner to close the system or jumper wires to battery. basically you need to power up the vent valve (one by canister) which closes it. purge valve in front is closed when not powered. Ive been a tech for 23 years personally if it were my vehicle I would get a new gas cap from the dealer (seen too many brand new parts store caps that leak) clear the cel and see if it comes back. before I waist any time checking things out. I would say 75% of the time its just a gas cap.

 

just realized as I clicked post that this is crazy old and his only one, hopefully he fixed his truck