Without knowing exactly what truck you're talking about I couldn't guess. And is it a new acquisition?

Ted

 

sorry about that it's an 06 Silverado 1500 with a 5.3 liter Flex Fuel hundred and thirty thousand miles I've had it since new absolutely no running problems or odors the fuel mileage has not changed either

 

evap purge valve next to canister open and still this issue I would then say it is the canister.

do you fill the tank up to max then park it in a heated garage or in a hot parking area after filling to the max... if so then the canister will get damaged from liquid fuel as well as the valves and tubing.

these vehicles are IMO designed poorly on the canister location. if you park with a full tank front end down the fuel pours into the canister.

 

I would say I would almost never fill it up and park it. Would drive about twenty miles after filling. And I park with the front end up hill most of the time

 

Back to your original post. If the nozzle shuts off it's because the pump pressure is higher than usual or the vent line for your tank is plugged.

Do you always use the same station and pump? I sometimes have the same problem with stations with new pumps. I either have to man the pump when fueling or usually I can insert the nozzle only 1/2" in the gas tank inlet. Also I have to set the pump on the slowest notch on the pump handle. It's inconvenient to man the pump because I use the time when fueling to clean the bugs off the windshield.

Edit: Solve the tank vent line and you'll probably correct the evap problem. If you have the pump cutoff at many/all stations it's a plugged vent line to the canister. The line may be crushed and cracked on the canister side. In that case it would appear open when you blow on it.

Ted

 

Thanks I'll check that out, but should I be able through the canister easily? Out of truck on tool box by mouth. I can also not blow back into tank through vent line that goes to canister. Can blow from filler neck and blows through vent to canister.

 

I don't know if there is a one way check valve in the vent line. I wouldn't think GM would put one in there. As you use fuel the fuel volume is replaced with air or at some point the pump in the tank couldn't overcome the vacuum. There should be a noticeable difference blowing toward the tank with the filler cap on versus with the cap off.

Ted

 

Found the problem! Someone tried to siphon my tank and nocked a fuel strainer loose that goes in the end of the metal filler tube and it was turned sideways in the hose. Thank you everyone for your help. Who would have thought.....

 

that is an odd one. good you fixed it..

 

Good job Sam and thank you for the feedback on finding the problem.

 

Good job. Very lucky, too. Sometimes the syphon hose will damage the fuel gauge and pump.

Ted

 

Back to your original post. If the nozzle shuts off it's because the pump pressure is higher than usual or the vent line for your tank is plugged.

Do you always use the same station and pump? I sometimes have the same problem with stations with new pumps. I either have to man the pump when fueling or usually I can insert the nozzle only 1/2" in the gas tank inlet. Also I have to set the pump on the slowest notch on the pump handle. It's inconvenient to man the pump because I use the time when fueling to clean the bugs off the windshield.

Edit: Solve the tank vent line and you'll probably correct the evap problem. If you have the pump cutoff at many/all stations it's a plugged vent line to the canister. The line may be crushed and cracked on the canister side. In that case it would appear open when you blow on it.

Ted

I was going to say the same exact thing. I'll bet that line is the issue

 

Hi could you share how you were able to see this was the problem and how you fixed it? I’m having problems with my Denali and have done everything to try to fix it

 

the truck GM year ?

 

2007

 

I have changed the canister the vent and the purge valve, the gas cap and still have a problem. I can’t pump without it stopping and now occasionally the dash will say that I need to tighten he gas cap the shop said I could drop it off and it would be like an exploratory deal where I drop it off and they just explore possible problems which we have already been doing it seems like because we have been throwing parts at the car and he problem still persists

 

so the gas tank of the rusted holes on the cap gas

 

The gas cap had a crack

 

check the purge valve by the gas tank ans see if it works i took mine off and tested it direct to battery with a amp meter jumper a to see if it works it should click and there is a purge valve under the hood also check that one. I also did a smoke test and found a leak and fixed it and since then no more problems. the evap system on these trucks is total garbage but what can you do. good luck you can buy a smoke tester on line for around a 100 bucks or less a valuable tool to have it will save you a ton in repairs in a garage