hissing gas cap

[7072f100]

hi everyone just got the 72 f100 running finally still working out bugs... after about 10 mins of running i shut it off and my gas cap was hissing pretty good. bad cap??? now heres the thing i put in a different tank. the tank i put in had a vent line on it where the truck didn't so i just ran a hose to the 2 little vents on top connecting them. there is also a big line running to the neck which is still connected. any ideas??? thanks!!!

[Dragon]

What tank did you put in? We don't know anything about your truck, So how can we help.

On our old tanks the cap allowed the tank to breath and they breath in only.

[fordman]

ok so you used your original filler neck and cap? if so dont worry. the tank needs to vent some how. the older tanks used the vented gas cap. the new tanks in 70 and up F100 used a nonvented gas cap and the tank vented through the charcoal canister on the front frame.

[Dragon]

ok so you used your original filler neck and cap? if so dont worry. the tank needs to vent some how. the older tanks used the vented gas cap. the new tanks in 70 and up F100 used a nonvented gas cap and the tank vented through the charcoal canister on the front frame.

My 71 did not have the charcoal canister. It needs the vented cap.

[Alvin in AZ]

My 71 did not have the charcoal canister. It needs the vented cap.

Same with my '75 F150. :)
No canister and vented caps that used to hiss and friggin spew gasoline too! :(

I had a heck of a time getting the correct rear gas cap from a Ford dealer.
They were accusing me (and the previous owner) of all sorts of stuff. :/
When I told them I was the only owner and the tanks came with the pickup,
well they talked-like they believed me but didn't work anymore towards
finding the right cap after that tho. LOL :)

"Ford never learned how to make the same part twice" -my Chevy buddies

Alvin in AZ

[Dragon]

"Ford never learned how to make the same part twice" -my Chevy buddies

That is because they never had to. It was right the first time. Chevy and Windows are alike the manuals are always asking are you sure you want to do this.

[R.Smith]

I bought a "vented" cap for for my 70 when I first got it but, the vent didn't work and it eventually caused the fuel pump to suck itself to death.