Behind the Seat Fuel Tank Problem

[JRBECK64]

I went out to my Sons 64 Yesterday to find a major problem. I was getting in the truck when I noticed that all the paint under the fuel nozzle was bubbled up and peeling off all the way down the cab to the bottom. I will post pictures later. My Question is has anyone had this same kind of problem and if they did "Other than moving the gas tank between the Frame Rails" how did you fix it? I sure dont want this to happen again. Red Paint is expensive.

JRBECK64

[lakeroadster]

These trucks have non vented gas tanks that require a vented gas cap. If you fill the tank all the way up with gas and then park it the gas will warm up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

My dad had a '72 C-20 that did this everytime until we learned to not fill the tank all the way up. My job as a kid was to fill up the tank when he got home. We had a gasoline storage tank with a hand pump at our "mini-farm" and I got good at listening to the sound of the gas goin' into the trucks gas tank and knowing when to stop based on the "sound".

The only way to "fix" the tank so it won't do this would be to install a vent line that is below the gas cap height. Then you can use a non vented gas cap. The gas will then leak out of the vent line instead of the cap.

Note: Make sure the vent is located such that when you fill the truck that the gas pump nozzle extends past it. If you don't gas will run out the vent line when you fill up the gas tank.

Since the 60-66 tanks have a seperate neck that attachs to the gas tank with a rubber hose you could remove the filler neck (the neck that sticks out through the cab) and have a 1/2" vent line tig welded into it (see sketch below). Then run a 1/2" fuel line from that down and out of the cab. You'd probably have to pull the tank to get the rubber hose off the neck.

Hope that helps.

John

[JRBECK64]

Originally Posted by lakeroadster

These trucks have non vented gas tanks that require a vented gas cap. If you fill the tank all the way up with gas and then park it the gas will warm up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

My dad had a '72 C-20 that did this everytime until we learned to not fill the tank all the way up. My job as a kid was to fill up the tank when he got home. We had a gasoline storage tank with a hand pump at our "mini-farm" and I got good at listening to the sound of the gas goin' into the trucks gas tank and knowing when to stop based on the "sound".

The only way to "fix" the tank so it won't do this would be to install a vent line that is below the gas cap height. Then you can use a non vented gas cap. The gas will then leak out of the vent line instead of the cap.

Since the 60-66 tanks have a seperate neck that attachs to the gas tank with a rubber hose you could remove the filler neck (the neck that sticks out through the cab) and have a 1/2" vent line tig welded into it (see sketch below). Then run a 1/2" fuel line from that down and out of the cab. You'd probably have to pull the tank to get the rubber hose off the neck.

Hope that helps.

John

John,
Last night after I vented a little myself I kind of came up with that thought of putting in an expansion relief or an overflow that would work much like the overflow in a radiator. Seems like a simple fix but taking out the tank is a pain. I guess its not as much of a pain as doing bodywork over and over again. Thanks for the info and I think that is what I am going to do to fix this problem. My Sons 69 Does the same thing but not as bad so I may do the same thing to his.

JRBECK64

[JRBECK64]

Hard to look at!!!

JRBECK64

[j.kirn]

I did the same thing on my 64 c-60 after i painted it ,it also was red

[lakeroadster]

Originally Posted by JRBECK64

Hard to look at!!! JRBECK64

Man..... that truly sucks.... damn! Was the paint fresh? My dads truck had factory paint but the gas never messed it up?

[nachodog2]

Originally Posted by lakeroadster

Man..... that truly sucks.... damn!

Ouch!
Posted via Mobile Device

[JRBECK64]

Originally Posted by lakeroadster

Man..... that truly sucks.... damn! Was the paint fresh? My dads truck had factory paint but the gas never messed it up?

The paint is about a year old. Im thinking it wicked up underneath the paint under the rubber gasket that goes around the fuel neck and the cab. I am going to take a few extra steps to protect it from this ever happening again.

JRBECK64

[astrochimp]

Originally Posted by lakeroadster

. You'd probably have to pull the tank to get the rubber hose off the neck.


John

You can remove & replace the hose with the tank in place. PITA, but probably easier than removing tank. IIRC I only removed hose from tank end, and pushed the neck in to the truck (bending hose to side) and installed the same.

[stsalvage]

Originally Posted by lakeroadster

These trucks have non vented gas tanks that require a vented gas cap. If you fill the tank all the way up with gas and then park it the gas will warm up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

My dad had a '72 C-20 that did this everytime until we learned to not fill the tank all the way up. My job as a kid was to fill up the tank when he got home. We had a gasoline storage tank with a hand pump at our "mini-farm" and I got good at listening to the sound of the gas goin' into the trucks gas tank and knowing when to stop based on the "sound".

The only way to "fix" the tank so it won't do this would be to install a vent line that is below the gas cap height. Then you can use a non vented gas cap. The gas will then leak out of the vent line instead of the cap.

Note: Make sure the vent is located such that when you fill the truck that the gas pump nozzle extends past it. If you don't gas will run out the vent line when you fill up the gas tank.

Since the 60-66 tanks have a seperate neck that attachs to the gas tank with a rubber hose you could remove the filler neck (the neck that sticks out through the cab) and have a 1/2" vent line tig welded into it (see sketch below). Then run a 1/2" fuel line from that down and out of the cab. You'd probably have to pull the tank to get the rubber hose off the neck.

Hope that helps.

John

Hello John 1971--72 Have vented tanks its part of the smog program every 1971--72 truck i have have vents and i was told and i did it to my locking gas cap all you have to do it drill the center of the gas cap and there is your Vent i did it to my 1965 3/4 ton I never have a problem with gas leaking out its only if your tank builds up pressure So my father used a small drill bit and breached the plastic and your done

[JRBECK64]

Originally Posted by stsalvage

Hello John 1971--72 Have vented tanks its part of the smog program every 1971--72 truck i have have vents and i was told and i did it to my locking gas cap all you have to do it drill the center of the gas cap and there is your Vent i did it to my 1965 3/4 ton I never have a problem with gas leaking out its only if your tank builds up pressure So my father used a small drill bit and breached the plastic and your done

stsalvage,
Thanks for the advice and that sounds a lot easier than what I was going to do. Can you just put a vented gas cap on it from a newer truck?

JRBECK64

[lakeroadster]

Originally Posted by stsalvage

Hello John 1971--72 Have vented tanks its part of the smog program every 1971--72 truck i have have vents and i was told and i did it to my locking gas cap all you have to do it drill the center of the gas cap and there is your Vent i did it to my 1965 3/4 ton I never have a problem with gas leaking out its only if your tank builds up pressure So my father used a small drill bit and breached the plastic and your done

If the tank already is vented, why would you want to vent the cap?

The leakage that JRBECK64 is talking about is due to the gas warming up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

Drilling a hole in the cap means it will again leak out of the cap in the above condition?

Think of it this way, if the tank isn't full and it builds pressure the vented cap is venting gas "fumes" not gas "liquid". JRBECK64's truck obviously was leaking liquid.

[oldtrux]

behind the seat fuel tank tank is a problem!

[JRBECK64]

Originally Posted by lakeroadster

If the tank already is vented, why would you want to vent the cap?

The leakage that JRBECK64 is talking about is due to the gas warming up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

Drilling a hole in the cap means it will again leak out of the cap in the above condition?

Think of it this way, if the tank isn't full and it builds pressure the vented cap is venting gas "fumes" not gas "liquid". JRBECK64's truck obviously was leaking liquid.

lakeroadster,
I think I am going to try to fit my 67 GTO gas tank between the back rails and get a licence plate that will pull down so I can fill the truck from the back. I am going to take the bed off anyway to do the bodywork on the back of the cab so with it out of the way it seems that would be the time to change it out. If that works I might just do the same thing to My Sons 69 Long Fleet. Paint is a lot more expensive that a new gas tank so I think I am going to make $$$$ be my motivator. Then I have to figure out where to put the spare tire??? Neverending problems.

JRBECK64

[lakeroadster]

Originally Posted by JRBECK64

lakeroadster,
I think I am going to try to fit my 67 GTO gas tank between the back rails and get a licence plate that will pull down so I can fill the truck from the back. JRBECK64

I understand totally. The only problem with using the license plate fill design is the gas tank will hang down very low. They are clearly visible from the side and the back of the truck. Some people don't like that look, some people don't care.

That look really bothers me so I used a 49-52 Chevy tank on my '65 for that reason, and a couuple other guys on the site here have done so too.

Check out the various types of tank installations here: The Rear Mount Gas Tank Thread

[Stew64]

This can be a common problem with straight enamel paint. Gas can eat it. If you use an acrylic paint that will usually stand up under gas spills.

[JRBECK64]

Originally Posted by Stew64

This can be a common problem with straight enamel paint. Gas can eat it. If you use an acrylic paint that will usually stand up under gas spills.

Stew64,
I used PPG base coat clear coat urethane. What I think happened is the gas leached under the Nozzle Gasket and it got under the clear coat and started eating from there. This Ethinol will eat through just about anything.

JRBECK64

[caddyhack]

Would this be fixed by running a vented cap or did the vented cap cause the problem?
Posted via Mobile Device

[lakeroadster]

Originally Posted by caddyhack

Would this be fixed by running a vented cap or did the vented cap cause the problem?
Posted via Mobile Device

The vented cap is the cause of the problem.

Originally Posted by lakeroadster

These trucks have non vented gas tanks that require a vented gas cap. If you fill the tank all the way up with gas and then park it the gas will warm up. As it warms up it volumetrically expands and if the tank is completly full it starts to leak out via the vented gas cap.

[JRBECK64]

Originally Posted by lakeroadster

The vented cap is the cause of the problem.

I am going to fabricate an Overflow much like the Radiator has so this will never happen again. Once I get the Nozzle out I will create a sump in the nozzle with a drain that will empty back into the tank on the top. I have a full gas tank so I need to drain it and fill it with water and flush it several times before I try to do this so I dont blow myself up. Thanks for the Info.

JRBECK64

[lakeroadster]

I don't think the return line will work. It works on a radiator because when a radiator cools down it pulls a vacuum which sucks the antifreeze in the puke tank back into the radiator. That won't happen with the gas tank. The puke tank will just fill up with gas and then you will be right back at square one.

But I may be wrong?

If you are dead set on trying it though you should be able to do the sump and the return all in the removable piece. Drain on the bottom, return on top, staggered so the return doesn't go into the drain.

That would eliminate you having to weld on the tank.

In regard to welding on the tank.... I worked at a place that repaired oil field equipment. We steam cleaned the vessels and then used a battery powered "sniffer" device on the vessel to ensure no explosive gases were present. Sometimes the vessels needed to be steamed out for hours to pass the sniff test.

Some radiator shops will do repair welds on gas tanks, might be better safe than sorry?

[JRBECK64]

Originally Posted by lakeroadster

I don't think the return line will work. It works on a radiator because when a radiator cools down it pulls a vacuum which sucks the antifreeze in the puke tank back into the radiator. That won't happen with the gas tank. The puke tank will just fill up with gas and then you will be right back at square one.

But I may be wrong?

If you are dead set on trying it though you should be able to do the sump and the return all in the removable piece. Drain on the bottom, return on top, staggered so the return doesn't go into the drain.

That would eliminate you having to weld on the tank.

In regard to welding on the tank.... I worked at a place that repaired oil field equipment. We steam cleaned the vessels and then used a battery powered "sniffer" device on the vessel to ensure no explosive gases were present. Sometimes the vessels needed to be steamed out for hours to pass the sniff test.

Some radiator shops will do repair welds on gas tanks, might be better safe than sorry?

Lakeroadster,
I think that I didnt exactly explain where I was going with the overflow Idea. I used the Radiator Overflow tank as the example but on this system I am going to bypass the overflow tank with a gravity feed back into the top of the tank. One of the problems these tanks have is the fact that the gas nozzle that is attached to the tank is extended into the tank instead of terminating at the tank. I believe that even when these tanks are full they are not really full to the top of the tank because of that extention into the tank. Now the question is will the pressure differential not allow the gas to flow back into the tank from the sump I am going to build on the gas nozzle. I guess only time will tell but you can bet I am going to keep a close eye on what its going to do after I implement it. Im not wasting any more red paint cause its way to expensive. Thanks for the heads up on the welding of the gas tank, and I think I might just take your advise of taking it to the local Radiator shop.

JRBECK64

[glos55]

Thanks lakeroadster! You are always quick with great information and pictures!!!!!!!!!!!!!!