Slow fuel fill, Gas smell. No codes.

[tucker12]

Hello Everyone.

I have a weird issue with my ol trusty rusty girl. 2004 gmc envoy XL (gmt370)

So to preface this, I have already replaced the fuel fill neck, gas cap, vapor purge box on the rear driver side of the tank, and fuel filter with Genuine Delco stuff. While I had her in the air for the transmission removal I checked my lines for leaks and smelled around and couldn't find anything. There are no error codes and I can command the system fully with the scan tool and as Far as i can tell everything works like it should. (since i can command the purge solenoid high enough to make the idle stall out)

Every time I get gas regardless of station, grade, weather I cant not put more than a few bucks in without it clicking off even if I hold the pump lever, hold the pump up, sideways it still does it. Now when i get gas I smell fuel around the middle of the truck near the driver side door but i cant find any leaks and it disappears by the time i get home and can look at it in detail up on the stands.

Should I find the charcoal canister and check that next? Where is it located. Its not where it is on my dads 2007 Trailblazer.

Any ideas?

Thanks in advance.
-matt

 

[Mooseman]

I went through a similar thing. The pump clicking off all the time could be a faulty vent valve and/or plugged canister and/or vent filter. If the vent is stuck closed or the canister plugged, it will regurgitate and click off the pump. It should be located atthe rear of the tank

The early EXT/XL had issues with the in-tank filler cracking and leaking so check around there. Heard of a couple later years starting to also do it probably due to age.

 

[tucker12]

So last week my dad and I were driving to Michigan to look at a boat and we stopped to get gas. As I was attempting to till up my dad walked back with snacks and noticed that something was leaking profusely near the front driver sided door. It was fuel. We went home immediately. Put the truck on stands and Dropped the tank to see what the hell was going on with not being able to put gas in and gas coming out everywhere.
And Behold, My stock 2004 GM Fuel pump. 215k miles

She was fully rotted through and underneath a inch or so of fuel on top of the lock ring. Somehow still pumping fuel. A real champ till the end.

So, I ordered new Delphi pump, Bosch filter, And new lines from rock auto. I cleaned the Pump ground, verified that all 3 plugs had power and were in good shape.
I also thoroughly inspected the vapor lines, blew them out with compressed air and verified everything is venting from the tank into the lines. I unplugged each with vent thing on top one by one and squeezed the tank and felt the air being pushed out. I verified the vapor canister had airflow thru it, verified the vent solenoid was good with a 12v on the bench, it opened and closed. Drained the tank, Filled up the power washer, lawn mower and every tank i own. Then I power washed the tank (lots of crud came out) and let it dry for a few days in the sun.

Yesterday after Easter Mass, We reinstalled the tank. New lines, another new filler neck, Filled her up and It still will not take more than 80 cents of gas at a time.

I climbed underneath at shell and unhooked the vent valve and even open to atmosphere it still wouldn't fill.
It took about 15 minutes to fill up about 20 gal.

My current theory is that the internal rollover valve is stuck or stubborn and the gas can't push it in fast enough and the gas fills up the tube and squirts out like it has.

This upcoming weekend im going to see if i can jiggle that valve with my fingers or something and see what's up. Maybe its stuck from varnish or just being old?
What's for certain is that my old fuel pump probably wasn't helping any. I'm just thankful I wasn't 3 hours away from my tools and stuff when she started spraying.

 

[flyboy2610]

https://m.youtube.com/c/NathanRohrbough

He has a video: Trailblazer hard refueling simple fix.

I'm on my phone right now and can't seem to get the link to copy.
I also seem to recall that Dorman came out with a replacement rollover valve. I believe it was Dorman, anyway.

 

[Mooseman]

Unfortunately the rollover/overfill valve is in the tank and is non-replaceable.

Since you opened the vent tube to atmosphere, that eliminates the charcoal canister and vent valve. Did you check to see if that vent hose actually does vent out? Maybe open it again and put some air pressure into the tank by the filler. If air comes out, then it's good. Also make sure the fill hose isn't kinked. I remember some have had that issue.

 

[Schurkey]

Not exactly the same issue, but I had to replace the fillter-tube-to-tank hose on my GMT360 because SOME of the gas pumps I'd try to use would shut off with very little fuel flow.

There's two versions of the hose--the one GM originally intended to use, that has a built-in check-valve; and the cheap piece of crap they actually used that doesn't. The hose with the check-valve is obvious; you can feel and see the bulge in the middle of the hose where the check-valve flapper is.

The updated fuel hose has a notch at one end, that fits into a molded plastic tab on the fuel tank. If the tab fits into the notch, the hose is oriented so that the check-valve works properly. The crappy hose without the check-valve is also notched, but there's no reason for it. The crappy hose doesn't need to be oriented in any particular direction, it works the same no matter how it's rotated. The fact that GM built locator tabs into the fuel tank tells me that they intended to use the (directional) hose with the check-valve. I suppose the bean counters over-ruled Engineering and made them shave thirty cents off the parts cost.

https://www.amazon.com/dp/B07TB5QK37/?tag=gmtnation-20