I got a “check gas cap” on my instrument cluster, then later CEL P0455 (Evaporative emission EVAP system large Leak Detected

 

AND?????
Was the cap loose?

 

Can you blow air thru the purge valve, the one under the hood?
Any damage to the canister under the car?
Fuel vapour line corroded?

 

Gas cap was not loose. I tightened it and reset engine light and check gas cap and p0455 came back.

how do I blow air thru purge valve, blow with my lips, hook up shop air, which direction am I supposed to blow?
no physical damage under the car. I did replace evap vent valve recently with the ac Delco replacement.
where fuel vapor line?

 

Fuel vapour line runs from the purge canister to the purge valve.
see if you can blow air thru the valve in both directions with you lips, it should be closed , no air passing thru.

 

Shop air blows thru evap purge valve from front of car toward back.
shop air does not blow thru evap valve from back of car toward front.

 

Hmm, it should be closed, no air in either direction.

 

Shop air might damage the valve, it is designed for low PSI vacuum. I have never taken one apart but my assumption is it is a gate/pin valve, impossible to flow in only 1 direction.

 

FYI I picked up a brand new GM AC Delco purge valve and I can NOT blow in either direction. I'll install it tomorrow. Side note: I am really really glad to see you guys here supporting everyone on HHR's even after so many years. Old Blue and DonBrew you guys are an absolute wealth of knowledge, Thank You!!

 

You are welcome