Chevy 5.3 slow pumping gas

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2005 Chevy Avalanche gas filler pipe not venting. Fill nozzle clicks off after pumping just a couple of seconds. From researching, it could be several things from the gas cap to the evap surge valve under the hood to the evap cannister at the gas tank. I have an appointment tomorrow at a trusted shop to have it looked at but I don’t want to just start throwing parts at it. I have tightened the gas cap but I feel it’s downstream from the cap as it still won’t take gas after trying to fill at different pumps several times. Can you guys suggest what the most likely culprit might be?
 
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Fuel cap will not cause slow filling. The most likely cause is a stuck closed, or partially closed vent valve. The second possible but less likely cause is a restricted charcoal canister. The purge valve on the engine will not cause slow fuel fill.
 

Strokenmerc

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Not sure what the specific cause of your issue is, but I have had similar issues filling my trailblazer. Not sure if it is related to the routing of the fill tube or not, but if I angle the nozzle handle 90 degrees there is no issue.

Edit - Filling my boat is a separate issue due to the horizontal fill tube that would make a saint curse.
 
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Does it do it no matter how slow/fast you have the nozzle set too. My 91 full size Bronco would never let me use the highest setting on the nozzle, it would keep shutting off so I always had to use a slower setting which was frustrating since it had a 30 gallon tank.
 
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Had that happen to me just once on my 2005 Yukon xl Denali, constant clicking and pumping gas was slow. The culprit was the evap canister blowing up and all the little black pellets going everywhere, had to drop the tank to clean them out. A mechanic friend told me it was most likely that issue and its usually caused by overfilling and pumping more beyond the first click which ill admit i always did but not anymore after. Tried his suggestion and it worked. Said it's common once you get near 300k. Happened to me at around 280k.
 
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Any EVAP issues can cause slow fueling - it doesn’t need to set off the CEL and throw a code. Modern fuel nozzles need to “see” a flow of vapor into the nozzle’s sensing port to allow fuel. It’s almost like the TXV in an HVAC system in some sense.

First place to check are the hoses between tank and EVAP module. Then the one-way “rollover” valve and work up from there before condemning the module.
 

gman2304

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The nozzle kicks off no matter how slow I pump or the nozzle orientation. I’m not getting any CEL or codes. I did get a chime and a (tighten gas cap) message in the dash info center. I’m leaning towards replacing the carbon cannister and the vent valve. I’m thinking the tank will have to be dropped which is most likely going to be expen$ive!
 
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I doubt it - the module and/or purge valve is mounted near the fuel tank in most cases. It’s a big, rectangular box about the size of a kid’s shoe box.
Yes the tank itself doesn't have to be dropped but it's suggested as that's where all the crap goes. What i did was run the truck till it fumed then threw just 2g's from a 5g can just to make it back and drop the tank. Made it much easier.
 

RAR

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Replacement of that valve on or near the canister is almost a routine yearly maintenance thing. Up here at least in northern Minnesota. If the salt brine of winter snow removal doesn’t get it, the gravel roads will take it out.

Easy to do… takes me about 20 minutes, and that’s including getting everything together, replacing the part, and putting my stuff away after. 🙂
 

gman2304

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I’m leaning towards replacing the carbon cannister and the vent valve. I’m thinking the tank will have to be dropped which is most likely going to be expen$ive!
^ My independent shop recommended and ended up doing this. Pulled the tank then blew about a million tiny carbon pellets from the lines on the top of the tank. Both Parts and labor came to $460. Pumped 15 gallons on the way home and didn’t click off until it was full.
Yes the tank itself doesn't have to be dropped but it's suggested as that's where all the crap goes.
^ This.
 
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On at least the GMT900 the vent line and its filter have been reengineered and relocated due to dust and grit getting into the hose.

This is something you can at least diagnose DIY-- look around underneath for a solenoid that goes to a hose that ends in a filter. Open the hoses up as much as you're comfortable... and look for crap in 'em.
 
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