Fuel tank venting?

[jjorgensen52]

I think this is the right forum.... anyhow.
My truck has started developing pressure in the gas tank. The longer I drive the worse it gets, to the point that when you open the tank it hisses pretty loudly for 5 - 10 seconds. It started doing that right about the same time I started having idle problems, so I don't know whats going on at all. I thought it might have been because a leak in the return drawing air, but fixed that and it got worse. Could it be that the charcoal canister is toast?

 

[Black Knight]

Re: Fuel tank venting?

possibly, just unhook the canister and see if it gets any better, make sure to plug the vacuum line at the TB, I think its at the TB youll just have to follow it back.

 

[QUICK STORM]

Re: Fuel tank venting?

i would suggest charcoal canister

 

[gjp]

Re: Fuel tank venting?

Mine did that once. I removed the canister Blew on it and air went throught it. I guess its ok. I re-installed. My truck still has a hickup at idle every so often. Soon as I get on it a few times it stops.
The canister vac line does go to the front TB under the linkage. There should be a check valve also.

 

[Syborg Twin Turbo]

Re: Fuel tank venting?

anyone have the plumbing diagram

 

[Don W.]

Re: Fuel tank venting?

Well I'm looking at it does that help? Anyway, it looks fairly simple. line from tank to canister. Line from canister to TB. HOWEVER there is a restriction shown in the line from the tank. Can't tell where that restrictor might be.

Based on your description I'd suggest that your "purge" valve on the canister is not working or the vac line to the TB is bad or the ck valve between the canister and TB is bad.

And why do I think there's a check valve in the vent line at the tank?

There's some good smog guys here that can prolly do better than the above mumbo-jumbo.:rotf:

 

[kentuc]

Re: Fuel tank venting?

Check valve prevents the engine vacuum from sucking gas out of the tank when it`s near full.

 

[jjorgensen52]

Re: Fuel tank venting?

Well I'm looking at it does that help? Anyway, it looks fairly simple. line from tank to canister. Line from canister to TB. HOWEVER there is a restriction shown in the line from the tank. Can't tell where that restrictor might be.

Based on your description I'd suggest that your "purge" valve on the canister is not working or the vac line to the TB is bad or the ck valve between the canister and TB is bad.

And why do I think there's a check valve in the vent line at the tank?

There's some good smog guys here that can prolly do better than the above mumbo-jumbo.:rotf:

I know there is no restriction in the vent line, it's been replaced and now it's just a piece of 3/8" stainless hardline... I have not disconnected the canister, I will see if that fixes the problem...

 

[VermontTy]

Re: Fuel tank venting?

What does the piece of 3/4" hose that runs next to the filler pipe do? I always thought that vented the tank somehow....

 

[kentuc]

Re: Fuel tank venting?

That vents the tank when it`s full to the top.

 

[jjorgensen52]

Re: Fuel tank venting?

What does the piece of 3/4" hose that runs next to the filler pipe do? I always thought that vented the tank somehow....

I figured that vent was for when you're filling it up. Now that I think about it, I'm not sure there's a check valve on the vacuum running to the can. Could that cause the motor to splutter at WOT / make some noises that sounded sorta like backfiring?