Emissions stuff

[Y2KpewterZ]

Vehicle is a 99 Yukon 5.7 4wd. Long story short bought the truck with a hole in the gas tank unbeknownst to me until I filled it up for the first time. No CEL for a massive evap leak though.

Replaced tank and installed new Delphi pump and ACDelco tank pressure sensor. This caused new issues to arrive. Truck would stumble and sometimes die after re fueling, also truck had a hard time starting after being warm (not a long cranking time, almost like the starter would stop spinning for a moment then kick back around) and p0446 kept popping up and noticed my tank was making a creaking noise and noticed pressure when I’d unscrew the gas cap.

I replaced the vent solenoid (Dorman) thinking that was the p0446 code and the pressurized tank issue. I also loaded the parts cannon while I was in there and replaced the purge solenoid (Standard) fuel filter (Wix) and gas cap. This fix lasted maybe two days until the hard start and stumble after refueling started again.

I disconnected the evap line from the tank that runs to the vapor canister and the truck runs great and no issues, except for the smell of gas. This led me to believe the vapor canister was clogged. Replaced canister (from a PnP, but I could freely blow air into it) and the hot start/stumbling issues were back. The truck would even cut off after idling for a few minutes. I also changed the vent solenoid with an ACDelco unit, still no fix. Unplugged the evap line from canister and truck runs great again.

Ecu issues here or am I missing something? Tia.

 

[Fless]

Does the tank still pressurize incorrectly?

Has the on/off command been verified for the vent valve?

Any purge/seal test done?

 

[east302]

Still have the code?

Here are the GM diagnostics for a 98, no guarantee that it’s the same for 99 but it may be worth a look.

 

[JackFox]

Would have thought a new purge valve would have fixed that. I see that happen to newer GM vehicles all the time. But same issue. Vlave is stuck open either slightly or fully, doesn't matter. When it is filled up it would spurt some raw fuel all the way up into the intake because pressure goes in all directions. Gas gets splashed around when filling and even though the vent valve is leaking off excess pressure (this is what causes a tank that won't fill btw), it still sends fumes and even raw fuel up into the intake. Not all systems would allow raw fuel even with the purge valve being stuck open. But I can tell you those 5.3L engine all do it!

I think you may need a new starter, but definately pull your right fender liner and take a look at that cable from the primary starting circuit. I work on stuff in michigan. I see those bad all the time. And when I diagnose cars, rarely is it ever just one thing! ha! People bring their cars in when it stops working. Not when something is wrong but the car still moves. You might think "who would do that?!?" Well... I cater to a certain market, consisting of people who are usually always broke!