Pressure in fuel tank-goes "pop"

[SquareRoot]

I recently added new 87 baffled tanks and replaced the ENTIRE fuel system to support my PF-4 EFI. One thing I noticed shortly thereafter was that my new tank would "pop" aka "tincan" anywhere from 20 seconds to 2 minutes after I shut the engine off.

Recently I have left the gas cap slightly loose and it seems to have fixed the issue. I have several different caps laying around so I tried several and get the same result.

I have been reading that gas caps only vent in one direction, sucking, e.g., allowing air in but not out. If true, my system should be completely sealed and the pressure is building up. I have a vapor cannister and it work's well. However, I "think" it has a vacuum valve that opens when the engine is started and then pulls the fumes from the tank vent line.

Anyone else ever dealt with this? I suppose the short answer is drill a hole in the gas cap. It's really not hurting anything, but it's annoying me knowing the tank is building pressure.

 

[rpcraft]

Maybe you have nothing but unvented gas caps and need a vented one? I'm no gas cap exert though.

 

[Bextreme04]

It sounds like you might have a plugged vent line. I suggest you see if air can actually freely make it to the vapor canister, you could have a clogged line or a bad canister that is keeping it from properly venting. Too many cycles of it pressurizing and releasing can cause the tank to fail and split.

 

[Vbb199]

I dunno which sender you're using. Or if it's dual, or a single. Or a big burb or k5 tank, but my single, 87 tank in my c10 I leave vented.

 

[bucket]

Vented caps are the answer for anything, IMHO. Except for a bunch of old cars with rear tanks and the filler is down low behind the license plate. That can be a problem under acceleration.

 

[CalSgt]

Vented caps are the answer for anything, IMHO. Except for a bunch of old cars with rear tanks and the filler is down low behind the license plate. That can be a problem under acceleration.

"How dare you"

You must be registered for see images attach

LOL

 

[Camar068]

It sounds like you might have a plugged vent line. I suggest you see if air can actually freely make it to the vapor canister, you could have a clogged line or a bad canister that is keeping it from properly venting. Too many cycles of it pressurizing and releasing can cause the tank to fail and split.

yup....I believe I have the same tank w/sender for the tank. My sender has 2 vent lines. You sure you didn't run one to the other and depending on the vent cap for vent?

[edit] sorry mine is the rear 'burb tank, but I would expect 2 vent lines coming off the sender.

 

[SirRobyn0]

Plugged vent line or something in the canister system not working right.

Keep in mind that yes the quick fix is drilling a hole in the gas cap, but you'll also invite moisture and stuff you don't want in there. With gas prices these days do you want to pay from some of it that ends up evaporating off.

Like Eric said you can check to make sure air will travel though the line, but beyond that whatever you have controlling the canister vent would be my suspect, and then of course the canister itself.

 

[Ricko1966]

I prefer a sealed system with properly working evap. That way I get to burn my gas instead of letting it evaporate and I don't pull moisture into the tank. Darn it I should have read Robynos post before I replied

 

[rpcraft]

I prefer a sealed system with properly working evap. That way I get to burn my gas instead of letting it evaporate and I don't pull moisture into the tank. Darn it I should have read Robynos post before I replied

Well, you only had 6 months. Things shouldn't be rushed right?

 

[Ricko1966]

Lol,sorry I keep forgetting to look at dates.Ill be looking at new posts and see the similar posts thing and tap it,forgetting thats not a new post.Gotta break my self of that habit.

 

[SirRobyn0]

Lol,sorry I keep forgetting to look at dates.Ill be looking at new posts and see the similar posts thing and tap it,forgetting thats not a new post.Gotta break my self of that habit.

Hey Richard, you have dug up a few older ones recently, but I think that's ok, even if the person has already solved their problem someone in the future might see it an find it useful. That's how I look at it anyway. I got to say I agree burn you gas! Don't vent it. it's to expensive to just vent off!

 

[rpcraft]

Sometimes people need to dig up old threads because the original poster never posted what solved their issue.