Vented gas cap?
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,281
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From: S/W Missouri, Polk county
Truck "should" be new enough to have a EEC gas tank. But the vent line coming off the valve (on top of the tank) gets clogged up sometimes. Have you checked it? So have you been having a "woosh" like a gas fume/ hot pressurised tank, when you take the gas cap off?
You would think most auto parts stores would have one, but most new gas caps do not work with the older truck lock ear depth on the fill neck. So if you go buy one try it in the parking lot. Or shop one of these vendors below.
Parts Vendors & Resources
Dennis Carpenter Ford Restoration Parts
National Parts Depot:Ford Truck Parts & Accessories | 1948-1979
MAC's Antique Auto Parts
Blue Oval Truck Parts
Jeff's Bronco Graveyard
LMC Truck - Ford Truck Parts and Truck Accessories
The Early Ford Store-San Dimas,CA
Truck & Car Shop (Orange, CA): 48-86 Ford Trucks, 66-86 Ford Bronco
C&G Early Ford Parts: 32-79 Ford Trucks (Escondido,CA)
Sacramento Vintage Ford
Flashback F-100s: 48-2008 Ford Truck Parts
Vintage Pickup Truck Parts & Restoration Resources Directory
Green Sales Company - Vintage NOS & OEM Parts
A wise guy once said..."There are two differences between the tanks. Tanks with EEC have a hole in the top center of the tank. A rubber grommet and check valve are pressed into the hole. A line goes from the check valve along the inside of the passenger side frame rail to the engine compartment where it hooks up to a charcoal canister. Non-EEC tanks don't have this hole. The other difference is the nipple for the breather line that is located right next to the nipple for the filler hose is located 180 degrees opposite.
If you are going from an EEC tankto a non-EEC tankyou must also change the fuelcap to a vented style. The EEC tanks are vented through the EEC system and use a sealed fuelcap. Non-EEC tanks vent through the fuelfiller cap. If you run a non-EEC tankand a sealed cap the minimum is you'll have fuelstarvation problems, at worst a collapsed fueltank."
You would think most auto parts stores would have one, but most new gas caps do not work with the older truck lock ear depth on the fill neck. So if you go buy one try it in the parking lot. Or shop one of these vendors below.
Parts Vendors & Resources
Dennis Carpenter Ford Restoration Parts
National Parts Depot:Ford Truck Parts & Accessories | 1948-1979
MAC's Antique Auto Parts
Blue Oval Truck Parts
Jeff's Bronco Graveyard
LMC Truck - Ford Truck Parts and Truck Accessories
The Early Ford Store-San Dimas,CA
Truck & Car Shop (Orange, CA): 48-86 Ford Trucks, 66-86 Ford Bronco
C&G Early Ford Parts: 32-79 Ford Trucks (Escondido,CA)
Sacramento Vintage Ford
Flashback F-100s: 48-2008 Ford Truck Parts
Vintage Pickup Truck Parts & Restoration Resources Directory
Green Sales Company - Vintage NOS & OEM Parts
A wise guy once said..."There are two differences between the tanks. Tanks with EEC have a hole in the top center of the tank. A rubber grommet and check valve are pressed into the hole. A line goes from the check valve along the inside of the passenger side frame rail to the engine compartment where it hooks up to a charcoal canister. Non-EEC tanks don't have this hole. The other difference is the nipple for the breather line that is located right next to the nipple for the filler hose is located 180 degrees opposite.
If you are going from an EEC tankto a non-EEC tankyou must also change the fuelcap to a vented style. The EEC tanks are vented through the EEC system and use a sealed fuelcap. Non-EEC tanks vent through the fuelfiller cap. If you run a non-EEC tankand a sealed cap the minimum is you'll have fuelstarvation problems, at worst a collapsed fueltank."
Last edited by 77&79F250; Apr 1, 2026 at 10:57 PM.
Thread Starter
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Cross-Country
Joined: Oct 2023
Posts: 66
Likes: 4
From: Monument, CO
No whoosh
No, I dont get the whoosh. I have the stock original tanks and use aftermarket locking gas caps from a local parts store that fit and latch just fine. The main reason for the question is trying to cover the bases after my issue with the motor bogging down on the road last week. Sounds like my tank must be venting ok, then, right?
Last edited by Dano76; Apr 1, 2026 at 11:12 PM.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,281
Likes: 5,824
From: S/W Missouri, Polk county
Motor bogging down, carb rebuild time, carb heat soak? Have you replaced the pre and post (of the fuel pump) fuel filters? When is the last time you have dropped the tank and clean it out, cleaned off the sending unit pick up tube sock?
Have you checked the gas cap to still be vented, a little bit of compressed shot in here and there migth chase out some dirt.
Have you checked the gas cap to still be vented, a little bit of compressed shot in here and there migth chase out some dirt.
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