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Where is all the air in my gas tank coming from??


MontanaChinook

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I know there will be some pressure, which is why the stock caps have vents.

I replaced my cap with a locking cap, and it must not vent.

BUT, ever since I took the Chinook out last weekend, the gas is overflowing.

I was smelling gas outside my house, and noticed that it was a little wet around the camper gas cap. I opened it up, and the gas is all the way up the filler neck, and serious bubbles are coming out, like when you get the air out of your radiator.

I've been opening the cap and doing this a couple times a day for two days now...

What's the deal? The tank is pretty full; I topped it off about 10 miles outside of town on my way home. But it has never done this the whole time I've owned it. I haven't driven it much since I put this new cap on, but I would never have believed that there would be this much air in a gas tank!

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I wonder if the vent hose is kinked or plugged, and gas is trying to vent out the filler hose ( if you even have a vent hose)

ALSO - Not sure about the year on your Chinook,

I would think, If you have a charcoal canaster, your gas system should be sealed so all venting happens thru the canister.. if you don't have a canister, I suspect it would be vented.

JD may have better info on this?

JOhn Mc

88 Dolphin 4 Auto

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It's a 78. Not sure if the tank is vented.

I was wondering about the charcoal canister.

Have people dropped their gas tanks in these trucks? I could do it no problem in my 83 4x4, but I could sit up under that truck. I can just barely slide myself under the Chinook, but I don't know that there's space to drop the tank without jacking it up. I didn't have much luck trying to get this thing up on jack stands last I tried...

So I'll blow into the charcoal canister to see if its plugged, and see if I can find out about a gas tank vent. I want to drop the tank and free up/clean the screen and sending unit this summer anyway, since my gauge drops to empty once I get below 3/4 tank.

Thanks!

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I doubt a 78 has a canister?

the tank may be just vented to atmosphere, and placing a sealed cap on it may be aggravating your problem.

John Mc

88 Dolphin 4 Auto

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it should have a canister on the fire wall maybe on the left side when standing in front. BUT do you still have your old gas cap if you put it back on and no problem it could be the cap . they may have sold you the wrong cap not vented write for that app might not show up in colder whether

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Any chance you filled it with cold gasoline from an underground tank and it then got warm and expanded? It's happened to me many times but stops leaking once I burn up some gas.

I just had the tank out of my 78 and there are no extra lines going to it. Just the fuel filler neck with a big and little pipe. The fuel pump module only has the pressure exit hose for fuel delivery. If you keep getting bubbles I'd suspect your electric fuel pump in the tank is leaking pressure where it's not supposed to.

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No idea! I did only notice it do this on my last fill. Didn't seem to do it the whole weekend on a fresh tank of gas, but has been after the last fill up.

I'll check things out.

I'll be looking into a new fuel pump anyways, just for insurance...

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