Fuel filler issue. This can’t be right.

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AuroraGirl

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This is my train of thought as well. Since the filler tube is bigger, it should flow gas at any rate, but due to the angle of the filler tube, the gas builds up in the flat, and splashes back. I tried every angle and flow rate and gas just wouldn’t go in. I’m no dummy, I’ve had old cars/trucks my whole life and I’ve never experienced this. I cannot understand or figure out how this filler was designed to actually work.
logic dictates you need to pull the filler neck and find out whats inside it.... theres literally only like 4 things between your nozzle and the open gas tank . One is removed to add gas every time.
 

Radiohead

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A variant of the ole potato in the tailpipe thing maybe? I could see how a shop rag, jammed down in the fill tube could cause problems. Gotts get a look and make sure zero restrictions. It had to work prior, right?
 

soliddrummer

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logic dictates you need to pull the filler neck and find out whats inside it.... theres literally only like 4 things between your nozzle and the open gas tank . One is removed to add gas every time.
The filler tube is wide open. But it runs uphill. The gas cannot get into the tank without pooling. It’s almost like a p trap under a sink. The filler tube has to be half full of fuel for it to trickle over the hump and down into the tank. This seems like a design problem. Both sides are exactly the same, something about this setup cannot be correct. Liquid does not flow uphill.
 

Ricko1966

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The filler tube is wide open. But it runs uphill. The gas cannot get into the tank without pooling. It’s almost like a p trap under a sink. The filler tube has to be half full of fuel for it to trickle over the hump and down into the tank. This seems like a design problem. Both sides are exactly the same, something about this setup cannot be correct. Liquid does not flow uphill.
Okay,but water still goes through the p trap of the sink,and fuel went into the tank of your truck for decades. I think you need to quit trying to think the problem away,and start taking some things apart and doing some investigating.
 

DoubleDingo

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New to me 1980 k3500 with saddle tanks. First time at the gas station after purchase and could NOT get gas in this truck. Put $20 in and $12 worth on the ground. Tried every which direction on the nozzle and just couldn’t get gas in this truck. Looked up underneath and both sides are like this. The filler hose runs UPHILL. So the gas just pools in the flat area and drizzles very slowly over the hump and into the tank. It took me 30 minutes to get a few gallons in. This cannot be right.
Maybe get new hoses for the filler, and cut an inch off the part that goes on the tank nipple? This may get it to be a downward slope
 
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DoubleDingo

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Okay,but water still goes through the p trap of the sink,and fuel went into the tank of your truck for decades. I think you need to quit trying to think the problem away,and start taking some things apart and doing some investigating.
It does because of the siphon effect. In this case the fluid is being forced at a higher rate than it can flow out to get the siphon working. But, I agree, filling it up has worked all these years, why not now.
 

Rickf

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Maybe trim a little off the tank end of the hose? Could it have been a C&C at some point and a bed installed? That could explain the geometry issue.
 

Bextreme04

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The filler tube is wide open. But it runs uphill. The gas cannot get into the tank without pooling. It’s almost like a p trap under a sink. The filler tube has to be half full of fuel for it to trickle over the hump and down into the tank. This seems like a design problem. Both sides are exactly the same, something about this setup cannot be correct. Liquid does not flow uphill.
It's hard to tell from your picture, but it doesn't look like that is true. I have an 80 K25 8600GVW with dual tanks just like you and Taylor. It looked just like your picture and had no issues with fueling at full tilt in either tank. You have an issue with an obstruction i neither the fill tube or the vent tube... period. You need to take the hoses and the filler off and figure out where the obstruction is. You need almost no horizontal drop for the fuel to flow correctly, so unless the filler neck has rotted or been mashed enough to drop it several inches lower than stock, you have a fill point that is several inches higher than the entrance into the tank and pooling should not be a problem.
 

soliddrummer

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I believe the next step as everyone else mentions is to do some dissassembly and see what is going on in there. The sending unit is bad on the passenger side as well, so two birds with one stone.
 

CountKrunk

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On my 84 c20 it doesnt drain fast enough for full tilt from the pump. I have to hold it like halfway. I don't get any fuel coming put of the neck but it must back up some as the pump you know detects the fuel and turns off.
 

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Had a hard time filling one of the tanks on my '90 C30. I changed the hoses, both fill and vent on both sides, as one of the vents had a small kink, and it solved the issue. Maybe an hour total for both sides and fairly cheap for all 4 hoses and 8 clamps. make sure you buy the correct pre-formed vent hose. I believe I got my stuff from LMC.
 

82sbshortbed

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I have to hold the nozzle upside down on the 82 for it to take gas without kicking off. But it takes it full flow after that. The 84 I don't have to do this. It just takes it normally. He'll if I know lol
 

AuroraGirl

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Okay,but water still goes through the p trap of the sink,and fuel went into the tank of your truck for decades. I think you need to quit trying to think the problem away,and start taking some things apart and doing some investigating.
couldnt have said it better
 

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