Charcoal Canister

[87-944S]

What are you guys doing with the hose from the fuel tank, the valve under the hood by the M/C and the hose that goes to the charcoal canister under the driver's fender? I'm trying to tie up all the loose ends.

[Bridar]

Funny, I asked the very same question some time ago on the PHB and no one answered it there either.

What I have learned is that you really don't have to do anything with it (which, I suspect, is what most people do). The vacuum canister is there to collect the fumes from the gas tank that would otherwise pollute the atmosphere as well as cause a fuel odor around the car or in your garage. You cannot just plug the hose comming from the charcoal canister, because it will need to vent the pressure, otherwise the extra pressure can screw up the running of your car. I suppose you could change the fuel cap to one of the old venting style ones, but again the fuel odor may be objectionable. What I did was to remove the Porsche vacuum valve and solenoid valve that are on the Charcoal Canister hose near the master cylinder. I then extended the hose to mate it with the solenoid valve that is attached to the LS1 head around the valve cover near cylinders 1 and 3. This seems to work fine, as I haven't had any fuel smell, though I have not tested it for all conditions---i.e.. for cold weather, after being parked in very hot weather, etc. As a side note, be aware that the LS1 computers had several different emissions control sensors for the fuel vapor system, including the charcoal canister. The GM cars had the ability to isolate the vapor system from the tank and then pressurize it and then test it for leak down. If it did not pass, it would throw a code. My understanding is that these codes can be programmed out of the computer and still keep the circuit that activates the charcoal cannister vent solenoid active.

Whew.....I must rest my keyboard now.

[87-944S]

Thanks for the reply, so did you use a tee fitting to connect the LS1 solenoid control to the canister and the fuel tank? That was what I was thinking of, would appreciate a pic if you have one.

Mike

[Bridar]

Mike,
No tee fitting is needed as it is just a straight hose. Refering to the picture, I removed hose 12 from vacuum valve 15 and solenoid valve 14. I then fit an extension hose onto hose 12 to allow it to mate to the cannister vent valve on the LS1 engine. The LS1 PCM controls the LS1 solenoid similarly to how the original Porsche set up was controlled, so it should work just fine. Of course, if you ever think that it is causing your engine to stumble, just unplug it and leave it open to the atmosphere (the tank side, that is). The engine solenoid side you may hav eto plug so as to avoid a vacuum leak.