benny852

Ok so about a month ago I replaced my cracked fuel cap on my truck with a cheap one from autozone. After that when I get fuel I noticed there was a pretty good vacuum when I removed the new cap (seemed normal). Yesterday I was under the truck and my fuel tank had been sucked in on one side I'm assuming the cracked fuel cap previous had prevented this from happening and now that I replaced the fuel cap its sealing and creating a pretty good vacuum and partially collapsing my tank. Whats the deal?

johnh

your tank vent is plugged

nickg

or your present fuel cap is faulty or the wrong one (gas) in the interm you can leave it a hair loose

infidel

The diesel fuel cap is designed to vent at 3 psi pressure or vacuum.
Gasser caps don't vent. You need the right cap.

benny852

K sounds good I had a feeling thats what it was. I will pick up a new cap. Im not sure where to get a cap that has the correct specs other than the dealer. ideas?

TRASHMAN

how ya do this ,mine is doing the same thing. drop the tank ??

Dinner

You will probably have to drop the tank. I'm not sure if there is enough room between the box and tank to stick your arm up in there or anything.

However this is what you are looking for, the plastic "spout" to the left of everything.

nickg

I could see and reach mine from under the truck, IIRC the "spout" can be rotated, mine was plugged full of dirt, I kept gently tapping it with a screwdriver handle till all the dirt vibrated out, I believe there is a link some where that says some trucks had a small cap installed at the factory and that it was susposed to be removed

TRASHMAN

thats the one i thought it was can you blow air thru it and not mess up anything?

Dinner

If there is dirt in there and you put the air to it, it will blow that dirt into your fuel I would think. I would try to take a small pick and dig it out, maybe take some brake clean?

BigIron70

I would clean the mud off of it first. Then spray it with WD40 blow it off with some air. If you can get a large screw driver or pry bar under it you can pop it out and clean it. Just sray some silicone spray on grommet first. Work it back into hole slowly or you will push grommet into tank. After installing put a piece of hose on it, a foot or so will work and it will help keep the mud out of hole. Good Luck