Smell of gas in the cab

[Jason Bourne]

Hello all, new to the site and I’m looking for some info.

My son has a 1972 V8 Auto C10 with EEC and the smell of gas in the cab. The 1st thing I am going to try is replacing the fuel sending unit gasket and all the rubber hoses that are connected to the gas tank. The fuel sender for my truck has 2 hoses that go to it, one is larger than the other. I assume the larger one (supply) is 3/8 inch not sure what size the smaller one (return) is?

The trucks fuel tank also has 2 rubber hoses on the passenger side (EEC) and 1 rubber hose on the drivers side that goes to the fuel neck. These hoses look all the same size. I assume they are 3/8 Inch?

Can anyone confirm if my assumptions are correct that they are all 3/8 inch? Also does anyone know the size of the smaller rubber hose for the return on the fuel sender?

[71CHEVYSHORTBED402]

Originally Posted by Jason Bourne

Hello all, new to the site and I’m looking for some info.

My son has a 1972 V8 Auto C10 with EEC and the smell of gas in the cab. The 1st thing I am going to try is replacing the fuel sending unit gasket and all the rubber hoses that are connected to the gas tank. The fuel sender for my truck has 2 hoses that go to it, one is larger than the other. I assume the larger one (supply) is 3/8 inch not sure what size the smaller one (return) is?

The trucks fuel tank also has 2 rubber hoses on the passenger side (EEC) and 1 rubber hose on the drivers side that goes to the fuel neck. These hoses look all the same size. I assume they are 3/8 Inch?

Can anyone confirm if my assumptions are correct that they are all 3/8 inch? Also does anyone know the size of the smaller rubber hose for the return on the fuel sender?

Fuel line is 3/8". Vapor line takes 5/16" PCV/EEC FUEL hose. I think you're on the right track to lose the fumes. Just as well replace the sender? These trucks are so old they're due new hoses, and senders too, IMO. My cab smelled of gas too, but I replaced everything short the tank, hardlines and separator.

I don't remember what the return line is, my truck doesnt have one. Seems it was smaller, 5/16" seems right, but not sure.

[Jason Bourne]

Originally Posted by 71CHEVYSHORTBED402

Fuel line is 3/8". EEC lines take 5/16 PCV/EEC FUEL hose. I think you're on the right track to lose the fumes. Just as well replace the sender? These trucks are so old they're due new hoses, and senders too, IMO. My cab smelled of gas too, but I replaced everything short the tank, hardlines and separator.

Thanks for your reply. Does the hose on the drivers side that runs from the tank to the fuel neck count as EEC? Is it 5/16 as well?

[71CHEVYSHORTBED402]

Originally Posted by Jason Bourne

Thanks for your reply. Does the hose on the drivers side that runs from the tank to the fuel neck count as EEC? Is it 5/16 as well?

That's 3/8" fuel hose as well. Seems that's so the tank doesn't get too full, not sure.

[Richard]

71chevyshortbed402 is giving good recommendations IMO. Though, myself I would leave the stock sending unit if it is working. No doubt the Chinese replacement is not the same quality as the stock one. The line that goes to the fuel fill is a vent line that allows air to purge while filling.

[howzzzit]

If you use the stock sending unit I would replace the fuel strainer on the bottom. When I pulled my sending unit the strainer was collapsed and fell off into the tank. That's a pisser. I was changing out the tank anyway. Looked like the sands of Iwo Jima in the bottom. On another side note. For years I could sometimes here something rolling back and forth inside the tank when cornering. Sounded like maybe a nut or something like that. When I removed the tank I looked for it. Nothing there. Aliens?

[71CHEVYSHORTBED402]

Originally Posted by Richard

71chevyshortbed402 is giving good recommendations IMO. Though, myself I would leave the stock sending unit if it is working. No doubt the Chinese replacement is not the same quality as the stock one. The line that goes to the fuel fill is a vent line that allows air to purge while filling.

Good point, and what howzzzit said, my filter was toast. I replaced the float as many recommend, with Jeep OMX-1772901 / 17729.01

Replace the rubber gasket regardless, it might be the very reason for the stench.

[Richard]

Originally Posted by howzzzit

If you use the stock sending unit I would replace the fuel strainer on the bottom. When I pulled my sending unit the strainer was collapsed and fell off into the tank. That's a pisser. I was changing out the tank anyway. Looked like the sands of Iwo Jima in the bottom. On another side note. For years I could sometimes here something rolling back and forth inside the tank when cornering. Sounded like maybe a nut or something like that. When I removed the tank I looked for it. Nothing there. Aliens?

Believe you answered the noise question in your post. It was the strainer floating around in the tank.

[howzzzit]

Nope. The strainer fell off as I was lifting the unit through the hole. I thought about someone messing with me and putting something in the tank, but always had a locking cap. You know. Like putting gravel in hubcaps, anti seize on door handle, long wire tie on drive line or a chicken in the back of a service van over the weekend. Not that I would know anything about these. Anyway the mystery sound is still part of the X Files.

['68OrangeSunshine]

I have a '68 C/10 Stepside with the stock in-cab tank.
No EEC.
The tank was replaced with a 1967 MY Tank in 1999 because the [then new] unleaded gas was dissolving bottom sediments and clogging my carb. Also the filler neck was chewed up when my locking gas caps key was lost, and had to be forced open. The '67 tank was identical and after a good hot tanking and thorough cleaning, worked great until about 2022.
Then the brass float ball sank and was replaced with the Plastic Jeep float. However, in taking off the tank's lock ring with a brass drift punch, I accidently broke the gas gauge terminal loose from its bond. I replaced the Sender with a used one my pal, Pat Moreland sent me, but I used the original rubber seal ring. Resulted in gas fumes. Especially after filling the tank with 20 gallons +.
I replaced the gasket with a new one from LMC, but I still got fumes in the cab.
I replaced the 10 - 12'' hose under the cab that links the fuel tank output to the fuel line to the fuel pump. Still getting fumes.

Is there an RTV type sealant that will seal off around that big O-Ring gasket?

[howzzzit]

The LMC gaskets are pretty thin. Don't know about others. Try 2 gaskets together. Maybe the locking ring isn't completely flat. Just a thought.

['68OrangeSunshine]

Originally Posted by howzzzit

The LMC gaskets are pretty thin. Don't know about others. Try 2 gaskets together. Maybe the locking ring isn't completely flat. Just a thought.

Be a few weeks until I get the fuel level down. I just filled up on the 29th because with supermarket promo points, I could buy regular at $2.19/gallon.

The gaskets are ~2'' O-Rings [with a short tail] so you could not double stack them.
After my mishap with the brass drift punch, I bought the Gas Tank Lock Ring Tool, P/N:32-4145. Setting the Sender in the tank pocket is super easy with it.
I can look more closely later, for a misalignment, but I'm pretty sure it went in right.
Before the Float swap, with a Non-Venting gas cap, the pressure would go whoosh if you pulled the cap off too fast. Now I use a cas cap that breathes.

EDIT: Here's a shot of the new lock ring in place. Gasket under it. Looks OK, but still getting gas fumes.

[Jason Bourne]

Wanted to give an update. Today my son and I replaced all the hoses and the fuel sending unit gasket. All the hoses looked pretty old and the fuel sending gasket was very flat. The fuel sending gasket we used was made by Spectra (bought off Amazon) and was pretty thick. Will give it some time but hopefully the smell of gas will be eliminated.

When we pulled the fuel sending unit the sock filter was missing. Tried looking in the tank for it but didn’t see anything. Made a quick trip to Orielly’s to purchase a new sock. When we put the new sock filter on it was very loose on the supply line. Was afraid it might fall off so I got a pair of pliers and lightly squeezed on the sock filters metal ring to create a little friction with the supply line. Not sure what is suppose to keep the sock from falling off.

I can confirm all hose sizes for a 1972 V8 with EEC.
The 2 EEC hoses on the passenger side of the fuel tank were 5/16 inch
The fuel sender supply hose was 3/8 inch and the return was 1/4 inch
The hose on the drivers side from the tank to the filler neck was 3/8 inch

[71CHEVYSHORTBED402]

Thanks for the update. The filter sock is supposed to be a press fit.

[54blackhornet]

I have been following this closely as I recently replaced the sender in my original style tank. The truck has no EEC being a C/20 built in Fremont. I have a aftermarket vented cap and funny thing never had a gas odor issue ever. Seems that the EEC equipped trucks have more of a gas smell problem than ones without ?

[71CHEVYSHORTBED402]

Originally Posted by 54blackhornet

I have been following this closely as I recently replaced the sender in my original style tank. The truck has no EEC being a C/20 built in Fremont. I have a aftermarket vented cap and funny thing never had a gas odor issue ever. Seems that the EEC equipped trucks have more of a gas smell problem than ones without ?

Probably

A mechanic I used back in the day ran the vapor line to a fuel pump return outlet. Add a "vented" cap - no issues or stench. The difference is, when operational the EEC reduces pollution, and probably adds a pinch more MPG.

I wonder how an operating EEC impacts engine performance, if at all? I don't know, seems the intake would welcome the contribution.

[howzzzit]

Originally Posted by 71CHEVYSHORTBED402

Probably

A mechanic I used back in the day ran the vapor line to a fuel pump return outlet. Add a "vented" cap - no issues or stench. The difference is, when operational the EEC reduces pollution, and probably adds a pinch more MPG.

I wonder how an operating EEC impacts engine performance, if at all? I don't know, seems the intake would welcome the contribution.

I just reworked and replaced my charcoal canister with an aftermarket can and external purge vacuum switch. I have it connected to a canister purge line on my quadrajet. (ported vacuum) Canister teed to pcv. I now have no gas smell in my garage. I have the smog pump removed so that's one less belt dragging on the motor. Doubt whether the canister vapors add any fuel economy, but anything would be an improvement on these gas hogs.

[Jason Bourne]

Came back to the thread to update. The gas smell inside the cab didn’t go away with the new hoses installed. I thought maybe the problem might be the EEC hoses that run up the passenger side pillar. I thought maybe the hose in there was old and cracked at that is why it was smelling. I decided to cap all 4 of those connections to see if that would help and my son drove the truck around for a few days.

It made the smell worse, but it helped us see what the real problem was. It turns out the tank has a leak. One of the first things my son and I did was to see if the tank had a leak but we didn’t see any. I think the tank has had a pin hole leak since he bought it. I believe the tank was building up pressure because the fumes weren’t being routed out through the EEC lines. I think this caused the leak to get bigger allowing us to see the real problem.

['68OrangeSunshine]

Something to think about...
I have a '68 MY with no EEC Frou-frou. I've replaced the Sender, the O-Ring. the belly hose, and the O-ring again, and I still get gas fumes.
The old float sank after a side collision in 4/22. The old sender got damaged -- terminal stud lost its seal -- when I used a brass drift pin and small ball pein hammer.

Fumes are strongest when tank is full.

What do I look for to spot a leak?

[Jason Bourne]

Originally Posted by '68OrangeSunshine

Something to think about...
I have a '68 MY with no EEC Frou-frou. I've replaced the Sender, the O-Ring. the belly hose, and the O-ring again, and I still get gas fumes.
The old float sank after a side collision in 4/22. The old sender got damaged -- terminal stud lost its seal -- when I used a brass drift pin and small ball pein hammer.

Fumes are strongest when tank is full.

What do I look for to spot a leak?

If the leak is tiny it may be hard to spot. For my sons truck we were able to see a small puddle after unbolting the bench seat and pushing it forward.

If you had a way of pressuring the tank it might be able to take a tiny leak and make it bigger so that it can be seen.

['68OrangeSunshine]

Originally Posted by Jason Bourne

If the leak is tiny it may be hard to spot. For my sons truck we were able to see a small puddle after unbolting the bench seat and pushing it forward.

If you had a way of pressuring the tank it might be able to take a tiny leak and make it bigger so that it can be seen.

Well, I fixed it.
Fault was my own.
I did not tighten the connection at the Gas Line/Fuel Level Sender behind the seat in the cab tight enough. I had to burn off about 15 gallons [out of a 20 Gallon Tank] to operate without gas spilling out of the opened line.
I had tried using teflon tape. I think that dissolved on contact with aromatic fuel vapors. I am not sure if I used the white teflon or the yellow teflon tape [recommended for Natural Gas connections].
I found the leak by looking for signs of wetness or vapor residue. I saw some streaks on the Tank, under the connection. Experimentally, I put a piece of white paper towel around the connection. One hot day later, that paper was wet with gas.
I cleaned up the threads on the fuel line with a wire brush. Some gooey residue forming into teflon shreds came off. This time I went metal-on-metal.
And I tightened it good.
I pumped in a 5 gallon can of 87 octane, then ran it into town and tanked up to Full. Took 10 more. I had put a loose gas cap -- one that didn't seal to let gas vapors vent out and not in the cab. Now with a full 20 inside, gas sloshed out the filler neck thru the cap. But 2 or 3 days later there is no fuel smell in the cab.
I put on a tighter gas cap too. Although it says Vented Cap on the decal, it always went WHOOSH! when I opened that cap.

[Stocker]