05 GMC Overflows Gas when Filling Up at the Pump

onecrazyfoo4u · April 28, 2016

My 05 GMC 1500 5.3l just started doing this the last 3 fill-ups. I thought it was a fluke, but it's now happened at 3 different gas stations. I've also tried the full flow nozzle setting, slow flow nozzle setting, and holding the gas pump nozzle by hand. Every time it won't shutoff right away...instead it keeps flowing for another 2-3 seconds, splattering a half quart of so of gas all over the side of my truck and ground. I've also tried with an empty tank, and half full tank...makes no difference on the results.

What would cause the gas pump to not click off right away? Is it something wrong with my fuel tank, lines, or tubes? Or is there some trick to get it to shutoff before overflowing and leaking everywhere? Just don't know where to start looking. Thanks.

00Silverado4x4 · April 28, 2016

Sounds like a problem with the gas station pump. Your truck isn't what tells the pump to stop the pump does.

onecrazyfoo4u · April 29, 2016

I can't imagine the same problem at 3 different gas stations. Doing some research it looks like a problem with maybe one of the small vent hoses in the tank nozzle. Or maybe a bad vent switch.

muddkatt · April 29, 2016

Every time it won't shutoff right away...instead it keeps flowing for another 2-3 seconds, splattering a half quart of so of gas all over the side of my truck and ground.

What would cause the gas pump to not click off right away?

From your post, I understand you to say that the pump is not kicking off for a few seconds, even though the gas has reached the top of the fill neck and is spewing back out. Correct?

Gurrzt · April 30, 2016

Sounds like the tank is not venting properly.

barry G · April 30, 2016

check codes for vent can, and the lines.

the tank thinks it is open someplace.

I would hope the truck is turned off too, while filling.

another one is thermal expansion, if you went through long term cold into crazy hot.

maine does this, but not even my 96 has overflowed..

try filling just shy of super full.

onecrazyfoo4u · April 30, 2016

That's correct, even though the tank reaches full, it takes a second or two for the pump to click off, allowing gas to overflow. I'll check the vent lines and blast them out with air.

My truck is always off while filling up. And I don't try to too it off ever, just fill till the nozzle clicks off.

HagiborChayil · May 10, 2016

buckets. i thought my 05 GMC Sierra SLT Z71 was the only one.... it has been doing it since I bought the truck over 6 years ago and drives me crazy. the only answer I have ever received was it is the pumps fault, which makes zero sense if it is every pump.

Definitely going to try this shortly to see because I hate wasting all that gasoline, not to mention it spills down the side of the truck onto my feet.

Only thing I have found that worked was getting the tank mostly full, turning it off and waiting a few minutes for things to settle then doing the last gallon or 2 slowly by hand, which doesn't always stop it from happening but does most of the time.