In cab gas tank venting

[Snake72]

Planning on reinstalling my original tank after a thorough cleaning. I have a 72 with the EEC venting and charcoal canister. I can remember this truck always having a faint odor of gas in the cab, worse on hot days. All the rubber hoses and clamps will be replaced, going to check for rust pin holes in the tank bottom but I think it's pretty clean for the original. Question is, I want to reduce the clutter and vacuum lines in the engine bay, the original charcoal canister probably hasnt worked correctly for years, can I just bypass the can and the vacuum lines to it? Can I take the vapor line that runs from the tank to the canister and leave it open to air under the truck?

I'd like to get rid of all the EEC lines and use a vented gas cap but have heard of gas spilling out and down the side of the truck with right turns, obviously dont want that. I don't really want to get a new charcoal canister, but don't want gas fumes in the cab either.

And I know a rear gas tank would solve these issues, but trying to retain stock tank.

[Swar]

The cap has to be sealed completely. The vent tube goes up inside the corner of the cab on passenger's side and back down through the floor. Mine just ends under the cab, never had a problem, just needs to be vented so the tank doesn't oil can from vacuum.

[sick472]

My vent is just like Swar describes, but I plan to add a fuel filter to the end of the vent line under the cab. I will cut the end off the filter so that it is more open. This way a mud dobber is less likely to fill the fuel filter tube with dirt and plug the system. I have also thought about using a sintered brass piece like an air valve muffler, but I have not thought about how to attach it just yet. Can't be too hard, just haven't got to it yet.

[Snake72]

perfect, thanks guys. I'll just end the vent under the cab

[Keystone_Hate]

Couldn't you just do away with the vent line all together and get a vented gas cap?

[Jeff's bowtie's]

Another way to cap off the vent tube under the truck cab would be to use a breather cap from a later differential

[Swar]

Originally Posted by Keystone_Hate

Couldn't you just do away with the vent line all together and get a vented gas cap?

I have yet to see a vented cap that does not leak when you go around a right hand corner on a full tank. That's why they changed it to the tube that goes up to the roof and back down so gas can never get passed it. Maybe there is a cap out there, but this is the easy, once and for all fix so you never have to mess with it again.

[demian5]

Originally Posted by Swar

I have yet to see a vented cap that does not leak when you go around a right hand corner on a full tank.

Didn't you mean 1/2 tank? LOL!

[Swar]

Originally Posted by demian5

Didn't you mean 1/2 tank? LOL!

Haha 1/2, 1/4, fumes, leaks every time!

[Richard2112]

Fuel venting requires considering all possible circumstances even the chance of a complete roll-over. Though none of us ever want to see our trucks with all the tires sticking straight up, ice and other road conditions have been known to cause the occurrence through no fault of our own.

Should a roll-over occur, one could assume that something pretty bad has happened and it probably didn't feel good. In a cab with multiple sprains and aches, the last thing one wants to think about is fuel spillage encompassing your vehicle.

Though the odds are against a complete roll-over, an unplanned severe angle situation can be nearly as bad.

Regardless of your method of venting, it's best to vent with all possible contingencies in mind.

[Swar]

Originally Posted by Richard2112

Fuel venting requires considering all possible circumstances even the chance of a complete roll-over. Though none of us ever want to see our trucks with all the tires sticking straight up, ice and other road conditions have been known to cause the occurrence through no fault of our own.

Should a roll-over occur, one could assume that something pretty bad has happened and it probably didn't feel good. In a cab with multiple sprains and aches, the last thing one wants to think about is fuel spillage encompassing your vehicle.

Though the odds are against a complete roll-over, an unplanned severe angle situation can be nearly as bad.

Regardless of your method of venting, it's best to vent with all possible contingencies in mind.

Actually, if you role it over, the vent under the tank is now on top of the tank, so you're good!

[Richard2112]

Originally Posted by Swar

Actually, if you role it over, the vent under the tank is now on top of the tank, so you're good!

I'll say this again...

an unplanned severe angle situation can be nearly as bad.

The best possible vent is one that completely closes at some predetermined angle (including 180 degrees). Many factory or aftermarket vents only work at certain angles and certain directions of list. Some only shut off completely upon full roll-over.

[Swar]

That was supposed to be a joke. I mean, you can worry about the what ifs, but driving these trucks, or anything old and with out air bags, is just the risk we take to enjoy life a little. Maybe there's a one way check valve you can get if you're doing some serious drag racing or drifting.

[Snake72]

In the event of a roll over, any in-cab gas tank is probably going to be bad news regardless of venting. Obviously a rear mount tank is probably the safest, unless of course rear ended, but at least you wouldn't showering in gasoline. I guess I'll do my best to keep the tires under the truck...no snow driving for this truck anymore.

The vented gas cap would be the easy choice, but again, too many people talking about spilled gas, with 1/2 tank even. I have new paint man, I'd be forced to slap myself repeatedly for spilling gas...

Planning to keep everything the same for EEC venting, just terminate the vent line under the cab with a breather of some variety (rear diff breather is a great idea). Will remove the line running all the way up to the engine bay, discard the charcoal canister and associated vacuum lines for a nice clean engine bay.

I can deal with some gas fumes in the garage, but not in the cab. If it doesnt work, I'll put the canister and lines back in.

[GASoline71]

Originally Posted by Snake72

Planning to keep everything the same for EEC venting, just terminate the vent line under the cab with a breather of some variety (rear diff breather is a great idea). Will remove the line running all the way up to the engine bay, discard the charcoal canister and associated vacuum lines for a nice clean engine bay.

This is exactly what I recently did when I installed my stock tank back into my 1972 GMC cab.

No smell, no nothin'.

Gary

[Keystone_Hate]

I ride a 58 year old motorcycle with a vented gas cap that’s exactly like the cap on my truck. Neither of which leak gas. As long as you have a good rubber gasket in there you’re fine.