Fuel Filling/EVAP issues tried everything please help

[MRPRO]

2005 Yukon Denali recently went to fill up put the hose in as usual tried to fill up and in a short time it cut off and fuel spilled all over the ground. Tried this several times and a different pumps same result.

I can put fuel in but have to do it very slowly. It would likely take 30 mins for a full fill up as slow as I have to go.

I read online about similar issues. To date I've replaced the vent valve solenoid, the fuel tank pressure sensor, the carbon canister, and the EVAP emissions canister purge valve on the front of the intake manifold.

I've blown out all the emissions related lines twice (both ends disconnected), as well as the fuel filler vent hose, and had the fuel tank out twice to do this.

The first time I did it and replaced all the parts and blew out all the carbon pellets I was able to fill it up no issues. I went to refill after I went through that tank of fuel and it was back to the same thing.

Today I went through the whole process again, blew everything out, nothing really came out this time, but the condition still persists. Can anyone help this is really frustrating, labor intensive and time consuming. What am I missing?

Also when I blow out the lines at this point I get no carbon pellets, yet when I go up to the emissions canister purge valve on the front of the engine and disconnect a few pellets will fall out and there may be some in the opening of the valve. I have no idea where they could be coming from at this point. If I leave the hose off and drive no pellets come out.

 

[OR VietVet]

First: Welcome to the forum from Oregon and please supply pics of the rig.

Before this started happening did you do any work at all to the rig? I mean anything. If you worked around the tank you could have done something. The system is not venting. When you do your repair attempt it is ok till it goes back to what is causing the problems. You replaced a lot of parts but why did you not renew all the evap lines. You may have a kink somewhere that is cleared when you blow air thru it but then settles back to kinked when driving and time goes by. Did you crawl under there and follow all the lines and get a good look at them?

Second:

We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[zbad55]

Well since you have replace all the parts to the evap system and still have the problem you may have an issue with the internal vent line. Did you replace the fuel module when you dropped the tank? When you get fuel spitback like you are seeing the reason is the fuel tank is not venting. There is a valve inside the tank located at the rear of the tank and that is where the FLVV (Fluid level vent valve) is located. There is a 5/8 line that runs from that to the underside of the fuel module. Did you blow that line out when you replaced the other parts and had the tank out of the vehicle?

 

[MRPRO]

Well since you have replace all the parts to the evap system and still have the problem you may have an issue with the internal vent line. Did you replace the fuel module when you dropped the tank? When you get fuel spitback like you are seeing the reason is the fuel tank is not venting. There is a valve inside the tank located at the rear of the tank and that is where the FLVV (Fluid level vent valve) is located. There is a 5/8 line that runs from that to the underside of the fuel module. Did you blow that line out when you replaced the other parts and had the tank out of the vehicle?

I blew out every line I could take apart and I understand why I'm getting fuel throwup, just can't figure out how to stop it. Is there a way to bypass it and do a workaround?

Fuel module/FLVV? What do those parts look like and where are they located? There was an off-white valve that looks to be pressed and/or glued into place on the top of the tank toward the inside of the tank about in the middle on top. I think that may be an issue but couldn't find a replacement, part number on it or description as to what it is. Has a line running to it that seems to be EVAP related and looks to connect to the fuel filler neck vent. I blew air into it both ways and it would seem to build up and then make a whistling sound once I removed the air source but I couldn't hear it too well over the sound of the air or compressor noise. Sounded restricted though.

 

[PNWYukon]

 

[ivin74]

There was an off-white valve that looks to be pressed and/or glued into place on the top of the tank toward the inside of the tank about in the middle on top.

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





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

 

[MRPRO]

post 5 doesn't really resemble the setup. the one below slightly resembles it. the circular valve toward the front of the tank near #5 looks like what i saw, but that's not where it was located on my tank.

 

[ivin74]

post 5 doesn't really resemble the setup. the one below slightly resembles it. the circular valve toward the front of the tank near #5 looks like what i saw, but that's not where it was located on my tank.

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?

 

[zbad55]

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,

 

[exp500]

I may be wrong again, but I was under the impression that getting charcoal pellets was a result of actually filling the charcoal can with fuel or age related disintegration of the cans screen. So if he already replaced charcoal can, blew out short line to manifold and is getting pellets again, new charcoal can is leaking pellets. Now the long vent line to the tank I can understand not getting all the pellets out with air, ( i use water first then air) Even then I have a tough time understanding why they never added a screen inline.Too complicated to be reliable built by lowest bidder again.

 

[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.