Pluuuuuuuease link the original thread so that we can combine them. Otherwise it'* like double diagnosis and going back and forth to figure out what was already looked at, suggested etc.

I tried to do that Bill but im an idiot, I cant figure out how...

This the thread you're talking about?

https://www.gmforum.com/showthread.php?t=289415

Thanks, I did put a brand new cap on, no diff, chgd the vent valve solenoid, no diff. With the hose from the cannister to the vent valve solenoid disconnected it kept the CEL on but never built any pressure for weeks. Put a new vent valve solenoid on and 3 days later pressure is back and CEL is on...

What about the evap cannister purge soleniod or the fuel tank pressure sensor ? Does the fuel tank pressure sensor send a signal to the vent valve to open ?? If so could that part be the problem ?

And what does the cannister purge do ??

Thx

from what I read the fuel tank pressure sensor just moniters the fuel tank pressure for leaks. But it does sound like the evap purge solenoid if stuck closed could be the problem, whacha think

I disconnected the wire at the purge solenoid and it has 12 volts going to it. I then disconnected the line from the canister and it blows clear, then the other line from the valve to the throttle body and it too is clear.
with the car running or not running there is no vaccum at either end of the valve and you cant blow thru it.

I alo broke the rubber connection at the throttle body and the end of the valve. Are these dealer items or jukyard or regular auto parts stores ??

**Old and new thread merged**

Thanks, the purge vavle is 214-641 about a 20.00 part. Think I should just chg it ?

does anyone know the function of the purge valve ? I drove the car for awhile and then removed the hose at the purge valve that runs to the canister and it has pressure in it.

Is this supposed to open when too much pressure is there and vent it to the throttle body or is that not how it works ??

Also wha does the fuel tank pressure sensor do ??