Gas tank help

[KT57]

Stinky in the 69. Shows leakage when the tank is topped off at the sending unit. But also no hoses for the vent. was wondering about hoses and routing and if anyone has pictures of how it should look. Also behind driver the vent line seems pinched off. What should I do ? Checking LMC confuses me a little. It gives options for with or without EEC. I am assuming this is a EEC tank. If that is so LMC says that these tanks are supposed to be 71 and 72. Is this a later tank or am I not understanding the EEC configuration?

[FRCvette]

I am going to follow along to see what replies you get. Have gas smell in my 70 cab too. Thought I had taken care of it when I replaced gas cap and new seal but still have smell.

[LongBox]

One point: My 69 only gets a gas smell in the cab when the tank is full, and I do a hard right turn, which causes fuel to slosh out the filler cap. The driver's window has to be open. Maybe you are getting the same thing happening. My 69 has no EEC.

I had a 71 that often had gas stink in the cab, no one could figure out why. That truck did have EEC.

[KT57]

Originally Posted by LongBox

One point: My 69 only gets a gas smell in the cab when the tank is full, and I do a hard right turn, which causes fuel to slosh out the filler cap. The driver's window has to be open. Maybe you are getting the same thing happening. My 69 has no EEC.

I had a 71 that often had gas stink in the cab, no one could figure out why. That truck did have EEC.

Can you answer whether or not mine is EEC?

[KT57]

Originally Posted by LongBox

One point: My 69 only gets a gas smell in the cab when the tank is full, and I do a hard right turn, which causes fuel to slosh out the filler cap. The driver's window has to be open. Maybe you are getting the same thing happening. My 69 has no EEC.

I had a 71 that often had gas stink in the cab, no one could figure out why. That truck did have EEC.

Can you answer whether or not mine is EEC?

[LongBox]

Does your truck have the charcoal cannister under the hood? That cannister will have vacuum lines and fuel vapor lines running into it at the top. If you have that, your truck has EEC. There should be an extra line from the tank to the cannister to vent gas fumes into the cannister.

I'm doing this all from memory, as my 69 doesn't have the EEC system, so if I've goofed this, some other member will correct any mistakes I've made.

[KT57]

Originally Posted by longbox

does your truck have the charcoal cannister under the hood? That cannister will have vacuum lines and fuel vapor lines running into it at the top. If you have that, your truck has eec. There should be an extra line from the tank to the cannister to vent gas fumes into the cannister.

I'm doing this all from memory, as my 69 doesn't have the eec system, so if i've goofed this, some other member will correct any mistakes i've made.

[KT57]

If you read my post it states tha LMC states that EEC was 71-72. But my truck has the vent lines nipples as you can see from my pictures. So unless I am off base, I have the incorrect tank. Can anyone confirm? My sending unit is leaking obviously and possibly the tank right behind the driver. Need to solve the problem and don't want to order wrong parts. Was it common to upgrade to the EEC tank? Did someone replace the tank with the wrong one? Come on guys. Where are the gurus with the quick easy answers.

[yuccales]

If that vent hose in your pic is cut off like that, I bet you smell gas! Your truck looks like an evap tank. Do you have a metal line running up the b pillar on the pass side? My old memory remembers that '69 307 Calif. emission 1/2 tons got air pump & eec tank & carbon canister etc. Some Calif. 350's had evap tank, some not. My '70 has an evap tank, original to truck, so some(california) got them before 71-72. If your going to keep all your emission stuff up and running, I'd replace all the hoses in the cab, proper gas cap, make sure vac line at carb is hooked up for the carbon canister. Before replacing your tank due to a leak behind driver (top corner vent hose?) make sure that vent line is not split. Hope you get that smelly truck fixed.

[Boog]

Lmc truck catalog has all the tanks and lines pictured to explain it for you. For a temp fix slide a short piece of hose over that pinched tube and clamp a bolt in it to seal off the smell. I imagine you can buy a new o ring for the sending unit to seal it too.

[KT57]

Originally Posted by Boog

Lmc truck catalog has all the tanks and lines pictured to explain it for you. For a temp fix slide a short piece of hose over that pinched tube and clamp a bolt in it to seal off the smell. I imagine you can buy a new o ring for the sending unit to seal it too.

Yes LMC has a diagram but shows only difference behind driver. Nothing behind passenger side where I have a hose cut off and no routing of anything. Plus it apparently throws me off by saying 71-72. I do not have a metal tube running down the pillar. Can anyone confirm that California trucks have EEC prior to 71? Wouldn't surprise me. California is always at the forefront of ruining a good plan.

[Boog]

Originally Posted by KT57

Yes LMC has a diagram but shows only difference behind driver. Nothing behind passenger side where I have a hose cut off and no routing of anything. Plus it apparently throws me off by saying 71-72. I do not have a metal tube running down the pillar. Can anyone confirm that California trucks have EEC prior to 71? Wouldn't surprise me. California is always at the forefront of ruining a good plan.

69's didn't have the eec tank. Yours obviously has been replaced with that one. With trucks 40+ years old there is no telling what all has been changed. Also worth mentioning is you need a vented gas cap or the pressure buildup can force seepage like you have.

[KT57]

That's great info! I'm also not seeing a charcoal canister any where. Probably just replace tank with correct original. Not quite ready to do a relocation.

[KT57]

Originally Posted by Boog

69's didn't have the eec tank. Yours obviously has been replaced with that one. With trucks 40+ years old there is no telling what all has been changed. Also worth mentioning is you need a vented gas cap or the pressure buildup can force seepage like you have.

Boog, sorry about that I totally glossed over your confirmation that I have an incorrect tank. So then my question is, Does a vented gas cap eliminate fuel smell? (If all other sources are sealed well)
And could an unvented tank cause fueling issues?

[yuccales]

Originally Posted by KT57

Can anyone confirm that California trucks have EEC prior to 71?

Yep, got a '70 in the driveway that does.

[Green72long]

New to group. I was looking around for info on cab leaks and saw this post about gas tanks. I have a 1972 c10 long bed and also have heavy gas fumes while driving. I was told that it could be the seal for the sending unit, so got a new seal and sending unit from LMC. I'm going to replace the rubber fuel lines in the cab when I drop in the new sending unit, it also looked like they were leaking. My gas tank is the EEC version with the charcoal canister and vent line behind the passenger, I can take photos if needed.

My question is, do I need to remove and drian the gas tank before I replace the sending unit?

[Boog]

Welcome to the boards. No need to drain the tank. That is unless the tank was just filled up. The sending unit drops in through the top of the tank so run the fuel level down below full.

[yuccales]

Very cool stuff you got with the truck!