NEED HELP large/small evap leak/ gas cap light/ stalls after refuel

[tyler]

So I've done a lot of research trying to figure out why my car stalls and has trouble starting after i fill up the tank. I've heard its because the fumes from the gas is going right into my cylinder combustion choking the engine. bad purge valve? I replaced my purge and vent valve already. It could be the new purge valve is faulty? Also I have been getting bad MPG as well. I also have engine codes stating that there are large-small evap leaks. Two separate codes. Trying to get the vehicle to pass inspection next month. doesn't really have a rough idle anymore for whatever reason. Also sometimes when my car idles and just reaches operating temp, it'll stall out. My buddy gave me a brand new oxygen sensor but I don't think that has to do with anything so I haven't replaced mine yet. can I blow in a purge valve to see if its stuck open, or is that trick just for the vent valve? Also when I'm fueling gas or if i start my car I can smell gas fumes around the vehicle.
Any suggestion on what I should do or where to look would be amazing!

Thanks!

 

[mrrsm]

Tyler... If you think of it... Please post the actual "P" Codes here that you recorded so we can all see precisely what they are. Did you replace your GAS CAP at the same time you did The "Valve" Jobs... and are we talking both of the ones in the engine compartment as well as the one near the back underside of the Gas Tank? I'm guessing you have already read this linked post... but if not... You might review what is here for any other helpful ideas... (Pay Special Attention to what @littleblazer suggests there in Post Message #8) And YES... Buying a Solenoid Purge Valve that is Inoperative right off of the Stock Room Floor at any Auto Parts Store is VERY possible because more than one Jackass has brought back the OEM Box to get their money back...and hidden their broken or damaged one inside... and after a lazy counterman re-stocks it uninspected ...and it lays in waiting for the next "victim" who needs to buy one.... a Sad Indictment of The Human Condition:

https://gmtnation.com/forums/threads/bad-gas-cap-or-purge-solenoid.16944/#post-532675

 

[tyler]

Got it, yes replaced vent valve in back and purge in engine compartment. Also replaced gas cap. I have a smoke machine, I might test for leaks in a week when time is available. I'll post codes in a little bit. I saw that YouTube video already in the link you have provided. he's showing how to test the vent valve, does that way of testing work for the purge as well?

 

[cornchip]

Buying a Solenoid Purge Valve that is Inoperative right off of the Stock Room Floor at any Auto Parts Store is VERY possible

A true statement. Happened to me with my wife's 2006 Equinox. Bought from a local NAPA parts store and inside the box an ACDelco part(reboxed) vent solenoid. Worked briefly and never completely went through the drive cycle to reset the monitor. I eventually gave up and told my wife to take it in. Cost her more than I'm willing to say. Even a new part can be bad.

 

[tyler]

A true statement. Happened to me with my wife's 2006 Equinox. Bought from a local NAPA parts store and inside the box an ACDelco part(reboxed) vent solenoid. Worked briefly and never completely went through the drive cycle to reset the monitor. I eventually gave up and told my wife to take it in. Cost her more than I'm willing to say. Even a new part can be bad.

Well I might have to test both valves then. Purge and vent. Because it smells and acts like its one of those. Been through a lot of parts with the TB, just never came across a faulty one that was "new."

Thanks guys I'll get back to you later and see what happens!

 

[Chickenhawk]

Hard starting after a fill up is also a common symptom of a bad fuel pump. Check the fuel pressure when cold.

Fuel pumps are mechanical devices, and they just plain wear out. Unlike other parts, they don't show symptoms of wear when they are working hard; they show the wear when fuel needs are low. It's like a vacuum cleaner or the blower fan in your car - if put on high, they work fine, but if put on low or first started, they have trouble kicking in.

Cold fresh gas causes a marginal fuel pump to not put out the same pressure as a pump that has been working hard. Strange, but true.