Fuel Cap tighten message

[latvius]

I keep getting the "tighten fuel cap" error alert. I used to have the problem of not able to fill gas tank. I have replaced the evap at the rear of the vehicle, the charcoal canister (blew out all the beads) and the one at the engine (dont remember the name of it). All this fixed my fuel fill problem. I also replaced the gas cap with an ac delco one.
I put a smoker on it and the only place smoke comes out is at the rear evap (I think this is normal??).

Assuming the smoke is supposed to come out the evap with engine off (I tried with key on as well) than I am at a loss on what to check next.

 

[Doubeleive]

Maybe try putting a factory gas cap back on it first, that's probably the cheaper option

 

[latvius]

Maybe try putting a factory gas cap back on it first, that's probably the cheaper option

Not sure if I have it still but I'll take a look when I get home.

 

[M1Gunner]

Purge valve (intake manifold side) normally closed, Evap vent (fuel tank side) normally open. So, yes unless you manually close the Evap vent with a scan tool then it’s going to be open. UNLESS it’s running a monitor in which it will close the vent and the pcm will continuously monitor the fuel tank pressure sensor.

When it comes to smoking the system, remove the schrader valve from the test port and use that to pump the smoke, DO NOT touch the gas cap, leave the vent valve open until you start to see smoke and then close the vent valve. The entire system should now be roughly filled, slowly check all lines from front to back. The reason you don’t want to disturb the gas cap is that it could be leaking and then when you fiddle with it the damn thing may seal properly.

 

[latvius]

"remove the schrader valve from the test port and use that to pump the smoke" Is that schrader valve on the purge valve?

"leave the vent valve open until you start to see smoke and then close the vent valve" Where is this vent valve?

 

[M1Gunner]

The Evap test port has the green cap on it. Looks like a little green valve cap. It’ll be on the Black Evap line that runs to the purge valve that is on the intake manifold.

The vent valve has to be commanded closed with a scan tool. It’s the Evap vent valve solenoid I believe is gm’s name for it.

 

[latvius]

Gotcha, I don't have a scan tool though...

 

[easterr]

Gotcha, I don't have a scan tool though...

I replaced the gas cap, the solenoid near the rear axle and the valve on the engine and that fixed it. Replacing the gas cap alone, the easiest of the 3, did not fix it.

 

[easterr]

I replaced the gas cap, the solenoid near the rear axle and the valve on the engine and that fixed it. Replacing the gas cap alone, the easiest of the 3, did not fix it.

I now see you've tried all these also. Sorry.

 

[latvius]

np, I have done some searches but did not find my answer.

 

[swathdiver]

Gotcha, I don't have a scan tool though...

Heading down the east coast of Florida anytime?

 

[latvius]

Unfortunately no, wonder if I should take it to a shop?

 

[swathdiver]

Unfortunately no, wonder if I should take it to a shop?

If you don't see anything obvious when you check the wiring then consider purchasing a decent scan tool that can read ABS codes. They have these little OBDII adapters that hook up to your phone via an app. Not quite Tech2 but might be enough to help. @randeez Randy here and some of the guys have these, let's see what they say about the capabilities of those things first.

 

[latvius]

I have one of those, I use torque app and have http://www.obdlink.com/lxbt/ the older version so I can erase the codes and scan them but it wont let me actuate anything advanced like that.

 

[KATfishing]

I had a similar problem... I replaced purge valve, vent valve/assembly and fuel cap, but each time I cleared the related code a new and different code would soon come up and became less specific (i.e. small leak, large leak, etc.). I took it into my local shop and they discovered a leaky fuel pump assembly... gasket was no longer sealing properly. New fuel pump kit made all the codes disappear. The codes point you in a direction, but the issue can be somewhere else in the system.

 

[latvius]

Interesting, I recently changed out the fuel pump because the fuel would bleed back down, bad check valve I believe. It came with a new o ring which I used but maybe a place to check.

 

[ssrobzoom]

The Evap test port has the green cap on it. Looks like a little green valve cap. It’ll be on the Black Evap line that runs to the purge valve that is on the intake manifold.

The vent valve has to be commanded closed with a scan tool. It’s the Evap vent valve solenoid I believe is gm’s name for it.

I'm fixing to replace my with AC Delco #214-1005 which does not have the test valve port. Because I'm getting the Gas Cap message also. The original one does should I get the one that does have it?? if so what the part number needed?? I have a 2005 Yukon SWB 5.3 non flex 2WD.