Gas tank vent/emissions system

[Paully's5.0]

Hey guys, for many years now I've been having problems with getting a gas smell in my car. I was autoxing once and on a hard right turn gas actually poured out of my tank. This happens anytime I have a full tank and take a hard right turn. When I fill up there is a lot of pressure that releases after I start to remove the cap. I have replaced the gas cap many times, can't find one that is vented either. I have replaced the filler neck and seal, I just don't know where to look. Can someone explain what vents got to the fuel tank, and if they can be replaced/bypassed so I can avoid the gas smell? In this hot weather it gets a lot worse.

 

[18mustangs]

Hey guys, for many years now I've been having problems with getting a gas smell in my car. I was autoxing once and on a hard right turn gas actually poured out of my tank. This happens anytime I have a full tank and take a hard right turn. When I fill up there is a lot of pressure that releases after I start to remove the cap. I have replaced the gas cap many times, can't find one that is vented either. I have replaced the filler neck and seal, I just don't know where to look. Can someone explain what vents got to the fuel tank, and if they can be replaced/bypassed so I can avoid the gas smell? In this hot weather it gets a lot worse.

I'm no expert, but since you replaced the filler neck seal and gas cap I'd check to see if your vapor line from the top of the tank that runs to the charcoal canister is hooked up to the nipple on top of the tank. If it is I'd check the vacuum lines running to and from the cannister and to the intake manifold to make sure they're not cracked.
Tim

 

[jrichker]

Your problem is a misssing or non fuctional carbon canister. The carbon canister system vents the gas tank. Disable the canister system or plug the vent line and then the problems you describe start to happen.

Carbon canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel.

It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?

 

[Paully's5.0]

Ok so i'm trying to track down the problem, and I've got good vacuum to the valve, but I get nothing after the valve. When exactly does the valve open? Is it controlled by a specific RPM? After a certain amount of time at an RPM?

 

[HISSIN50]

Not sure if it is what you meant, but the purge solenoid opens while idling, etc, to vent the vapors into the intake.

 

[Paully's5.0]

So basically as soon as the engine is running the solenoid should open? and I should get a good vacuum reading? Whats the sense in a solenoid controlling the action when a direct connection to the canister would do the same?

Just trying to understand the system so I know how to diagnose the problem and fix it! Thanks!

Oh, anyone know what the voltage is for the solienoid? I could easily bipass the trigger to open and test it that way. Then I could see if that part is actually working.

 

[jrichker]

Solenoid uses 12 volts.

The computer provides the ground, the power comes from the injector power by way of the ECC relay.

 

[HISSIN50]

I am not sure if it was mentioned, but a quick thing to check is the vac line that goes under the front of the plenum. That line comes from the CC and is very prone to vulcanizing and allowing a leak.

At the CC, I would note that atleast one vac line has a different I.D. on one end vs the other (you might have trouble finding a new one so dont yank too hard on the stocker).

Good luck.

 

[Paully's5.0]

I checked for the vacuumon that line you are talking about, had a solid 17 so i don't think there are any leaks.