Problem Filling Up Tank

steve04z71 · May 4, 2008

I have a 2004 GMC with a 5.3 v8. I am having a problem filling the gas tank up. When fueling up at a gas station I cannot get gas to go into the tank very fast. I have to fuel up VERY slowly "like 1 gallon takes 3 minutes". I took it to a dealership and they didn't kow what was wrong so I replaced the gas tank with a new one. Unfortunately this did not solve the problem. I know our trucks are equipped with the EVAP system, could this cause this problem??

any ideas?

cammiller · May 5, 2008

Yes, there is no vent back up the filler hose, rather the air flows through the evap canister. I would suspect the canister is plugged with dirt. If you are going to replace canister, then get the updated valve from GM and put the vent filter under the hood using 5/8 heater hose.

ChevyTech007 · May 5, 2008

Second that.

FuzzyDriver · May 6, 2008

OK, you have the exact same year/engine GMC truck that I have and I had the EXACT same problem. I am having trouble believing you replaced the entire gas tank without first determining that that was the problem, but I'll let that slide. I'm also troubled that the dealer didn't know what could cause it. Once SparkTech turned me on to the ONLY fuel tank vent path that exists for our trucks, the answer was fairly obvious.

Assuming you have the same problem, it will be a stuck-shut VSV (Vent Solenoid Valve). To verify this, remove the quick-disconnect fitting on the hose that runs between the charcoal canister and the VSV. This is a molded, hard-plastic tube. The VSV is mounted to the plastic gas-tank shield, at the rear of shield (between the gas tank and the differential). The disconnect is at the cannister end of the tube. There are two fingers on a plastic retainer piece that you push up on to remove the retainer, then the disconnect comes apart easily.

Once you get the hose off, leave it off while you try to fill the tank. If it fills normally, viola! Go to the GMC dealer and get a new VSV. They will sell you the kit to relocate the VSV exhaust filter along with a new VSV. They are about $140 , which is just ridiculous IMO. And you can't just leave it off, you will get a nasty EVAP System "Large Leak" engine code.

You can chuck the rest of the kit and just replace the VSV (not recommended) or you can follow the instructions and put the new exhaust filter up by the transmission and run 5/8 heater hose back to the VSV. I did neither. Running heater hose through the frame rail was more than I wanted to do, so I ran the heater hose up to the fuel inlet and tie-wrapped the new VSV filter way up high inside the fender by the fuel filler, facing down so splashes couldn't get to it. I have the hose itself sitting on top of the fuel tank. I have not received any engine codes since I did this fix.

Here is a link to my troubleshooting and fixing efforts: http://www.gm-trucks.com/forums/index.php?showtopic=77906. I hope you find it useful.

FuzzyDriver

cammiller · May 7, 2008

I am still having issues putting the filter next to the trans, I run it up beside the master cylinder.

FuzzyDriver · May 8, 2008

I am still having issues putting the filter next to the trans, I run it up beside the master cylinder.

I was concerned that, if I used much hose, the tank wouldn't vent fast enough during filling and the gas would back up in the filler tube and trip off the pump. That's why I elected to keep it as short as reasonable and still get it up high. The only other thing to be careful about, where I put it, is that if there's too much hose up there it could whap around inside the fender when you hit a bump.

I have to agree with you about putting it next to the trans. I evaluated that real close, since that's what the directions said to do, then it was "Naaaah, I don't think so....".

cammiller · May 8, 2008

I have put the vent on EVERY truck I have fixed next to the master cylinder, using between 13' to 18" of hose and not 1 has come back, my own included! As for the routing, I send it along with the harness and tie strap it in place.