Scootin159

does anyone know where I could get a brief outline of how the system works?

potent951turbo

When you say "open" are you referring to the purge valve opening? I am talking about removing the purge valve and having the line from the tank going straight to the cannister.

Just trying to clarify here.

Spidey944

As I understand it, the Purge valve opens with the vehicle reaches a set temperature, and the vehicle it at cruising speeds, or on throttle closed deceleration (dont quote me on that 100%). The temp sender under the intake opens and allows vacuum to reach the purge valve near the fuse box. When the valve opens, fumes from the tank are vented into the charcoal cannister, and expelled.

Scootin: I will try and find you some print info on this system.

potent951turbo

If that is correct, then I don't see where there would be any problems from venting the tank straight to the charcoal cannister. Then you could remove the purge valve, vacuum lines, and the tube running to the j-boot. If there is a problem with this then someone feel free to correct me.

eniac

Because your 20 year old canister is probably half to fully clogged and needs vacuum to pull anything through it. ATM pressure alone might not be enough to let it vent. That is why I opted to remove everything all the way back to the tank. I saved quite a bit of weight as well.

Spidey944

Thanks Stephen for the help. Also, if your cannister is blocked off everywhere except the line from the tank, and there is no help drawing the fuel vapors into it, why would the fumes not just stay in the tank? It needs some help from engine vacuum to circulate.

Scott: i dont have any literature on the system in print. Just a diagram showing flow etc.

EDIT: the system also purges on initial start up to vent vapors that occur while not running.

Spidey944

After looking at the diagram for a while, it would appear that the vapors get pulled through the cannister then gets sent back into the j-boot to be recycled. One would think that on a turbo car this would mess with AFR's a little bit as it is being added AFTER the AFM/MAF.

potent951turbo

Well here is another question, if you pull off the rubber line that connects to the hard line on the firewall is the tank free to vent from that hard line or do you need to remove more stuff at the tank end?

Spidey944

Vapors will escape slowly, and only as they build up enough to force themselves out. You need engine vacuum.

shiners780

As I understand it: When the engine isn't running at temp, the expanding pressure in the fuel tank pushes fuel vapor into the charcoal canister. Once the engine is up to temp, the thermal valve opens causing the purge valve to open, which in turn causes the fuel vapor to be diverted into the intake to be burned off.

I removed everything back to number 30, and stuck a small filter (similar to the one pictured) on the end to prevent it from getting plugged up.

The only thing the vacuum does is divert the fuel vapor into the intake instead of allowing it to go into the charcoal canister. The fuel tank will still vent off excess pressure without the vacuum system in place.

UncleMaz

That looks like a clean solution. Did you also use a vented cap or is that redundant?

shiners780

Your post wasn't directed at me, but if I may: As long as the vent line coming off the fuel tank isn't blocked off, you don't need a vented gas cap.

potent951turbo

Thankyou for this info!

Everyone was talking about removing everything and then trying to say you need vacuum, which didn't make sense if your talking about removing the stuff.

UncleMaz

Thank you Shiners

eniac

It is a closed system(sort of) and that is one of the reasons I removed the purge system and the crankcase recirculate system so they now both vent to atm rather then affecting my AFR. As long as they are vented, then pressure in my crankcase and my gas tank will always be equal to atm pressure. This is quite fine. I do not want a negative pressure in either one and of course positive pressure would be a very bad thing as well.

If you car is not running and the tank builds excessive pressure, it will still vent to atm.

Yes, I did something similar to Shiners below, one because I felt the extra line was not needed and two, because if I was going to get a fuel vapor smell, I did not want that coming from the engine compartment.

So far I have not had any fuel smell coming from any part of the car.

This is exactly what I did as well except I used a cute little red filter from the ricer isle at pepboys. It's like a mini K&N. This is my anti-rice since it now sits just above my gas tank where no one but me will see it. lol