Pressure in the gas tank

[Scarab]

I notice when I take the gas cap off I have pressure coming out of the tank. I found the metal line under the hood that has a 90 degree turn up that A hose that used to go to the charcoal canister when to and I tried blowing air through it and I could not blow air through it. Does it have a one way check valve? Maybe that is why I cant blow through it but it should vent I would think. Just trying to find out why it is not venting.

 

[Royal-T-Ltd]

Could be a bad gas cap. They go bad and the venting doesn’t work. Worth a shot - it’s a cheap fix.


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[pacecarta]

cap is not supposed to vent , if you dont require to be smogged you could replace with a vented one
there is a poppet valve on the vent in the hat of the sender with a light spring but it should allow air in and with 1-2psi should vent

vent line is mostlikely plugged with rust

 

[Scarab]

Could be a bad gas cap. They go bad and the venting doesn’t work. Worth a shot - it’s a cheap fix.


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I bought a replacement from Napa and it was a vented cap, but I think it is only vented for vaccum and not pressure as it will let air into the tank but not out. I went back and checked and this is the cap they show for the GN. I even thought about drilling a hole in it. LOL back in the late 80's I used to watch video of my car leaving the line and gas running out of the tank. Wish I had that old cap from back then.

 

[Royal-T-Ltd]

I bought a replacement from Napa and it was a vented cap, but I think it is only vented for vaccum and not pressure as it will let air into the tank but not out. I went back and checked and this is the cap they show for the GN. I even thought about drilling a hole in it. LOL back in the late 80's I used to watch video of my car leaving the line and gas running out of the tank. Wish I had that old cap from back then.

Also forgot to mention - yes there is a check valve on the hose that leads to the charcoal canister.... Make sure its facing the correct direction.

aaron

 

[pacecarta]

Also forgot to mention - yes there is a check valve on the hose that leads to the charcoal canister.... Make sure its facing the correct direction.

aaron

check valve should be replaced if its bad but you cant pressurize the tank with a bad check valve to the solenoid ..the canister is open at bottom

 

[mikes86ttop]

Check out the rubber line from pump to sender... Mike

 

[Scarab]

There is no canister on this car, just a metal line with a 90 in it pointing straight up near
the air filter. Cant blow through it. New cap bought for GN and it is vented but only to vaccum not to outside. What I am saying it can draw air in but will not let it out if pressure is built up. So no hose on this car. I was thinking the metal line may have had a check valve in it at the tank, but if not then it could be clogged up.

 

[pacecarta]

the 5/16 line above axle with spring clamps is the vent you can disconnect it under the shield and see if problem persists . if you want you could put a vacuum brake filter on end (its charcoal filled )

 

[Royal-T-Ltd]

There is no canister on this car, just a metal line with a 90 in it pointing straight up near
the air filter. Cant blow through it. New cap bought for GN and it is vented but only to vaccum not to outside. What I am saying it can draw air in but will not let it out if pressure is built up. So no hose on this car. I was thinking the metal line may have had a check valve in it at the tank, but if not then it could be clogged up.

I guess blow pressurized air through the vent - at least that way your sure there’s no blockage and your not second guessing yourself. Maybe first follow the vent line and make sure it didn’t get crimped along the rails or anywhere else. - aaron


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[Chuck Leeper]

DO NOT reverse blow that line. If it's plugged w/ crap, it goes in the tank!

 

[Royal-T-Ltd]

DO NOT reverse blow that line. If it's plugged w/ crap, it goes in the tank!

Yeah ONLY blow from the back forward.... i hope he understood that from my post.

i guess these days you have to be very specific.

 

[hensleyt]

Mine was plugged,I tried blowing both ways tank off with 125 psi could not get it unplugged.
I run the canaster so I ran a fuel line front to back solved the problem.I do not have any idea where to vent to safety but a lot of people through the canaster away.

 

[Scarab]

ok guest I will pull the line off at the tank and run a vent hose up near the tag and put a filter on the end of it. Anyway to tell which hose it is under the heat shield without tracing lines all the way to the front?

 

[pacecarta]

nobody listens anymore and everyone has their opinions
..its 5/16 with spring clamps as i posted earlier
return is 1/4" with single hose clamp, feed is 3/8 with dual hose clamps

 

[Royal-T-Ltd]

ok guest I will pull the line off at the tank and run a vent hose up near the tag and put a filter on the end of it. Anyway to tell which hose it is under the heat shield without tracing lines all the way to the front?

The biggest one is feed - the second biggest is Vent the smallest is return..... yeah don't ask why.


Just like pacecarta mentioned.