Quote:
Originally Posted by Low Elco
Are you still there, Bruce? Hope the truck is treating you well, I have a couple questions? On P. 13, you ran a vent line to the front of the truck from the tank. What did that go to? Having gas smell problems in the garage. Thanks in Advance, Chip
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Hi Chip
The vent line I ran to the engine compartment from the gas tank went to the vapor canister (I call it a charcoal canister), this is part of the evaporative emissions control system (EEC). You didn’t say what year truck you had and this could be the reason you have a gas smell problem in your garage.
First it needs to be said that all gas tanks need to be vented in some manor, important to say again all gas tanks need to be vented in some manner. If it’s not vented you will not be able to get the gas out of the gas tank to feed the engine without collapsing the fuel tank from the vacuum that would be created from drawing the gas out of the tank (very unlikely to create enough vacuum to collapse the tank normally you just starve the engine for fuel because it will not flow thru the line).
There are two different vent systems that can be found on the 1967 – 1972 trucks. The first one is found between 1967 – 1969, I would call this venting thru the gas cap. If this is the system you have the smell of gas in your garage could happen and there’s nothing you can do to prevent it. The smell of gas might not be as noticeable when the truck is parked outside but because the gas cap vents into the atmosphere and the vapors need to go somewhere it could be noticed outside also, but in a closed garage the vapors are more noticeable. Another problem that can be noticed with this vent system is when you have a full tank of gas and run over a bumpy road or going around a corner and the liquid gas gets up to the cap some gas could dribble out thru the vent hole and down the side of the truck. (Note changing a vented cap system to a none vented cap system without thinking about the whole vent system will not work, no you can’t just change the cap).
The other vent system (EEC) could be found on the 1971 – 1972 trucks (I can’t say all of them, it all depends on what state the truck was originally sold in and as always if the system was changed by someone back to vented cap system). Basically this system is not vented into the atmosphere thru the gas cap but the fumes and venting is thru the vapor canister. The canister collects any gas vapors and then when the engine is running any vapors that have been collected in the charcoal is drawn off and burned in the engine (you don’t have the smell of gas in the garage). You can change a (EEC) system to a vented cap system but you need to think about all the components of the system and where you block them off. You can’t change a vented cap system into a (EEC) without changing the gas tank and adding some components to make it a functional EEC system.
My truck is a 1972 that had an EEC system and I wanted to retain it even with the relocated blazer style gas tank and this is the reason I ran my vent line to the engine compartment.
My personal opinion is before making any changes to your fuel tank vent system you need to understand what all the various components do and make sure there all there and doing what their supposed to be doing to have a safe and functional system.
Hope you find this information useful and if you would like any additional information just ask.
Enjoy your build
Bruce