Fuel Filling/EVAP issues tried everything please help

[MRPRO]

Where on the image below is the white valve you are taking about. I have never seen it.

View attachment 258606



Did you use oem parts? When I change out the vent valves on my Denali I used Autozone junk and they only lasted 3 months, the second time I used OEM parts and I have not had them go out in 3 years

Combination of oem and oreilly parts. The vent valve on the charcoal canister is from oreillys. The canister I believe is from eBay and is Delco. The fuel tank pressure valve is Delco and the purge valve on the intake is Delco.

 

[MRPRO]

If you are talking about the white cap like the picture shown below, that is not a valve it's just a vent. Did you blow the lines that go to the intake manifold?

View attachment 258610

Yes that’s the white cap I was talking about. Do they go bad are they serviceable? Lines on the intake? Is there more than one? The only one I blew out is the one that goes to the purge valve and the one that still produces pellets when hooked up and removed. If left unhooked no pellets.

 

[MRPRO]

Post# 5 is not a SUV fuel tank it is the 26 gallon P/U tank. Post#6 and #8 is the correct tank, the external valves that your see that is white is GVV (Grade Vent Valve). If you look at the back of the tank that black disc that it is welded to the top is where the FLVV is located. And this is where the internal 5/8 line is plumbed to. That valve controls the height of the fuel and allows the tank to vent when filling. There may be an issue with this or the line is plugged, if that happens then you can not vent the tank,

Ok if it’s this how do you fix it?

 

[zbad55]

This video may help, you need to make sure that you blow out all the lines on the tank as shown. Make sure the 5/8 vent line is clear also, hope this helps. Even though this is a Tahoe the fuel system is the same,

 

[MRPRO]

This video may help, you need to make sure that you blow out all the lines on the tank as shown. Make sure the 5/8 vent line is clear also, hope this helps. Even though this is a Tahoe the fuel system is the same,

That’s the exact process I’ve done twice now. Is there more than one hose up on the intake? Which one is the 5/8 vent valve? If it’s the FLVV/internal 5/8 line how do I fix that? It also gives me a code P0455 and tells me to tighten the gas cap.

 

[PNWYukon]

Apply smoke to the EVAP system at the service port until the leak is located.

 

[MRPRO]

Apply smoke to the EVAP system at the service port until the leak is located.

What's considered the service port?

Also, is there more than one hose up on the intake?

Which line is the 5/8 vent valve?

If it’s the FLVV/internal 5/8 line how do I fix that?

It also gives me a code P0455 and tells me to tighten the gas cap.

 

[PNWYukon]

• A fuel fill cap that is left OFF after a fuel fill will cause this DTC to set.
• A loose, missing, or damaged fuel fill cap can cause this DTC to set.
• A blockage or restriction in the EVAP purge solenoid, purge pipe EVAP canister, or vapor pipe, can cause this DTC to set.
• A temporary blockage in the EVAP purge solenoid, purge pipe, or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system.
• To help locate intermittent leaks, use the J 41413-200 to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT.
• To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT.
• Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

 

[MRPRO]

What's considered the service port?

Also, is there more than one hose up on the intake?

Which line is the 5/8 vent valve?

If it’s the FLVV/internal 5/8 line how do I fix that?

It also gives me a code P0455 and tells me to tighten the gas cap.

 

[Denali12]

This info is based on my experience with the 2012 Denali....

If the tank has been dropped it's HIGHLY important that the line in the photo be routed over the frame rather than under. Many owners & mechanics have made this mistake. You can put eyes on it be removing the rear wheel on the fill side & taking out the wheel well plastic.