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.

[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.

[yuccales]

Originally Posted by KT57

That's great info! I'm also not seeing a charcoal canister any where.

Take a look under the battery. Do you see a black coffee can looking thing with some hoses hooked to it?

[KT57]

Originally Posted by yuccales

Take a look under the battery. Do you see a black coffee can looking thing with some hoses hooked to it?

Negative. Now I see in LMC all of the other lines. I don't have any of it. Plus my fuel pump looks eerily similar to LMC's picture of a pump for a inline 6. Oh I never mentioned my starvation or vapor lock issue I'm having.😳

[Boog]

Also in looking over the LMC tank, lines and sending units you will see a difference in line diameter. 6 cylinders use a 5/16" supply line, single outlet fuel pump. The V8s have a 3/8" supply line, a dual outlet pump with a 1/4" return line to the tank. I think this will head off vapor lock issues and have my 69 setup this way.

[KT57]

Originally Posted by Boog

Also in looking over the LMC tank, lines and sending units you will see a difference in line diameter. 6 cylinders use a 5/16" supply line, single outlet fuel pump. The V8s have a 3/8" supply line, a dual outlet pump with a 1/4" return line to the tank. I think this will head off vapor lock issues and have my 69 setup this way.

68-71 1/2 ton 307 pumps are a different p/n than all other V8's except 67 283 and 327. Anyway I bought one because even if it's the same a $25 back up is handy. So the new pump looks to be identical to what is installed. It has a single inlet and a single outlet. I have no return lines in my truck at all. Don't even see any place to attach a line. So my question is, is my tank correct? Do 67-69 tanks have vent lines at the top corners of the tank as my pictures show? If so can someone show me a picture of how these lines are routed through the cab? I'm lost.

[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?

[Boog]

The return line goes into the tank sending unit. I'll get a pic of mine if you like.
The tank will fuel just fine. The vented cap should remove most of the in cab smell. There have been discussions about vented/non vented caps on this forum too.

[KT57]

Originally Posted by Boog

The return line goes into the tank sending unit. I'll get a pic of mine if you like.

Ok I see it my picture at the top. Where does it start under the hood?

[KT57]

And also does your pump look like mine? If your engine is anything other than a 69 307 then I suspect not.

[FirstOwner69]

I have a '69 3/4 ton with a 350. It was made at Fremont, CA, in Dec, 1968, and sold new to me in Yorba Linda (southern California). It never had EEC with no holes in the tank other than the hole for the fuel pump and no tubes other that the fill tube for gas. The pump has one inlet and one outlet and looks like the one pictured. The gas line is 3/8". I would say you have the wrong tank.

[KT57]

Originally Posted by FirstOwner69

I have a '69 3/4 ton with a 350. It was made at Fremont, CA, in Dec, 1968, and sold new to me in Yorba Linda (southern California). It never had EEC with no holes in the tank other than the hole for the fuel pump and no tubes other that the fill tube for gas. The pump has one inlet and one outlet and looks like the one pictured. The gas line is 3/8". I would say you have the wrong tank.

Thank you sir. That's what I suspected. Mine was made in Fremont April 69.
Any fuel smell or venting issues? Do you have a vented gas cap? And was it a stock item?

[FirstOwner69]

Originally Posted by KT57

Thank you sir. That's what I suspected. Mine was made in Fremont April 69.
Any fuel smell or venting issues? Do you have a vented gas cap? And was it a stock item?

Vented cap was standard. Only fuel smell is when turning right as noted in a post above if tank is full and gasket on cap is shot. I suppose there may be some slight smell due to venting, but negligible.