Gas tank won’t fill

[ben82k10]

I went to fill up my gas tank. Stopped like it was full and it’s not. I got about 2.5 gallons in. It has dual tanks but the left side is the but the fuel selector valve needs to be replaced. The guy I bought it from said the right side is the primary tank. The google said it was the left side. Which one is it? And any idea why it won’t get much more than 2 gallons in it? I put about 2 more after I got home from my gas can.

 

[75gmck25]

Easy reason for your confusion.

On my ‘75 the right side tank is primary. However, at some point (not sure of the year), the left side became primary.

The angle on the metal tube of my tank fillers is at a very flat angle and the gas backs up to the pump shutoff. I always have to set the gas pump at the lowest level and let it dribble into the tank.

 

[Turbo4whl]

If the charcoal filter gets clogged, this can cause a filling issue. Purge valve (on the charcoal can) could be bad. Fuel vapor okay, if raw fuel gets sucked in it will melt the charcoal.

 

[Grit dog]

Doesn’t matter which side is primary for filling purposes.
Assuming it’s original type configuration, newer vapor recovery nozzles are super finicky to get gas into these tanks.
Old style normal nozzles work fine.
Likely your issue?
I can fill any of the 4 square body tanks with a new style nozzle but it has to be held just right and low flow. Old nozzles work fine.

 

[ben82k10]

If the charcoal filter gets clogged, this can cause a filling issue. Purge valve (on the charcoal can) could be bad. Fuel vapor okay, if raw fuel gets sucked in it will melt the charcoal.

Where’s the charcoal filter? This is my first square body so don’t abuse me too much

 

[ben82k10]

I tried the slowest and different angles and it still clicked off and spit gas out. I did notice how flat the neck is. I’ll look more in my garage where it might get to 40*. Mid 20s and stupid wind got me to say words I shouldn’t have and drove home.

 

[Turbo4whl]

The charcoal can, mounted on the inner fender near the radiator. As stated, check the fill and vent hoses at the tank fill.

 

[Grit dog]

I tried the slowest and different angles and it still clicked off and spit gas out. I did notice how flat the neck is. I’ll look more in my garage where it might get to 40*. Mid 20s and stupid wind got me to say words I shouldn’t have and drove home.

Which type of nozzle? That is significant in your diagnosis or lack of an actual issue with the truck. And whether it is actually vented or not. It’s an old truck. I’m all but certain by the 80s all were 3 port fuel senders but doesn’t mean it still is today.

 

[ben82k10]

It has to be in the filler neck. I can hear gas in the tank. No kinks or leaks. I couldn't add anymore even with a gas can.

 

[ben82k10]

Ok, I removed the filler neck. That’s fine. All the fuel seems to be sitting in the hose that connects to the tank. It’s blocked or something not letting the fuel get into the tank. I’m trying to remove that hose clamp but it’s not the normal hose clamp. It looks like a bolt that’s holding it on to a clamp. Any idea what could be the cause? I’m going to replace that part of the hose and see what I can see. Hopefully I won’t need to drop the tank. Pretty sure I will end up having to though.

 

[ben82k10]

I took a hose and put it into the passenger tank to see if there was a blockage. No blockage. It seems to be full but sounds empty when I tap on the tank. Maybe the guy I bought it from told me wrong and it’s the left tank that hooked up. How can I tell without topping off that tank and being right back where I started. He told me the switch in the cab works, it the fuel selector valve to switch tanks need replaced. I’m at a loss.

 

[Dejure]

SIDE NOTE: My old 3/4 ton, 71 fleet side Chev had three tanks. Don't want to think of how much it'd cost to fill all three today.

That aside, I had to make a run to the coast to deliver a half side of beef to a friend. That's about a 600 mile round trip. To that end, I filled all three tanks. It was the first time the other two had been used in several years.

I don't know why, but I had two fuel filters in the tool box. Glad I did, and that I had tools (e.g., pliers). I had to use them. They were the see through type filters and you could see they were packed with rust. That warned me of what I needed to prepare for in the future, if I used the other two tanks again.

 

[Grit dog]

@ben82k10
Well at least you don’t have 3 tanks like the anecdotal story posted above.
But what you do have is a lack of complete information presented and need to stop co-mingling issues.
Is this about getting fuel in the tank or which tank it’s running off of?
I’m sure this can be difficult as you must have just bought the truck and not put gas in it until now.
But again terminology and lack of info keep from anyone being able to help solve your issue.
If you stuck a hose down in the tank did it come back all wet or a little wet? That’s that difference between full or almost empty.
Even easier if you filled the filler hose. First determine that.
Next gotta see which tank it’s running off of. Since your switcher switch or solenoid is apparently messed up, it’s easy to figure out th old fashioned way.
Clamp one supply line closed and start the truck. If it doesn’t die in a minute or less then it’s not the one feeding fuel.
Good luck.

 

[ben82k10]

Well the tank is full. So that leads me to believe I’m actually running off of the driver side tank and not the passenger side tank like he told me. Not upset. It’s easy to get little things like that mixed up. I’m going to trace the lines back from the fuel pump and see if that helps me determine if it is in fact the driver side tank. Now, another question I have is, do dual tanks have some sort of overflow or something in case you top off one tank it will go into the other? I ask because I’ve only put in gas on the passenger side because that’s what tank I was told was the main/functioning tank. I don’t want to top off the drivers side tank and half to drain it all out if I need to drop the tank or tanks.

 

[YakkoWarner]

Well the tank is full. So that leads me to believe I’m actually running off of the driver side tank and not the passenger side tank like he told me. Not upset. It’s easy to get little things like that mixed up. I’m going to trace the lines back from the fuel pump and see if that helps me determine if it is in fact the driver side tank. Now, another question I have is, do dual tanks have some sort of overflow or something in case you top off one tank it will go into the other? I ask because I’ve only put in gas on the passenger side because that’s what tank I was told was the main/functioning tank. I don’t want to top off the drivers side tank and half to drain it all out if I need to drop the tank or tanks.

I don't think the tanks have an overflow (been a while since I had a dual-tank rig) but I belive it IS possible for the switching valve to get out of sync or have the seals get loose and allow the fuel return to go to the tank that the fuel is not being drawn from. This is old memory so may not be 100% but might be a way fuel transferred from one tank to the other.