Evap Code po440 concerns
 

I have a 1999 Cheverolet k1500 5.7L 120,000 miles that was giving me a po442, then a po440 code about once a week or so. I replaced the vent solenoid, the purge solenoid, went with a gm gas cap, and had the system smoke checked. I even had both after the converter o2 sensors replaced. Everything is checking out good. It finally stopped and today 3 months later the light came back on and I checked it and again it was a po440 evap code.
Does anyone have any ideas on what I can do next? The vehicle has about 3/4 of a tank of gas in it and I run shell v power in it so it doesn't ping, also the temperature outside was about 88 and muggy, and when it came on was at a noon start up. I took the truck to work this morning with no problems, came out to go to lunch and as soon as I started it the light came on and stayed on. I reset the code already but this is getting frustrating. I also want to add that my vent solenoid is located on the evap canister under the hood and my purge solenoid is located on the passenger side of my intake manifold. I also have replaced the fuel pump 2 years ago and this just started over this passed winter. Any advice is appreciated.

Thank you
Greg A
email: go2agym1@woh.rr.com

Well I took the truck to a local shop here in town that does all aspects of auto repair. This is the same people that have put on the purge solenoid the vent solenoid, and repaired the leak on the canister and then smoke checked everything and this time they again checked all the parts by turning them on and off manually with their hand held scanner and also done another smoke test and they even disconnected everything and re-plugged it back in and they can not get it to do it again. They are kind of aggravated at it and they told me not to worry about it and just drive it till it finally goes bad or what ever its going to do.
Again I ask does anyone have any suggestions?

Greg Agee