Code P0455 and won't start

[wolfpack]

2008 Yukon, 5.3L

Code P0455 and cranks forever after removing the gas cap, for example after filling up. Takes 2 or 3 tries to start it, then it's fine.

What do I look for? Don't want the mechanics playing the guessing game on my dime as always.

Thanks!

 

[sumo]

Any other codes? P0455 means a large leak detected. How's the seal in the gas caP? Never heard of that code causing a no start.

 

[wolfpack]

P0455 is the only code. The gas cap is tight.

 

[wolfpack]

It was the EVAP purge valve in the engine compartment. $26 part, easy swap out- just careful with the plastic plumbing attached to it b/c it's flimsy as heck.