Originally Posted by Injuneer

As pressure builds in the tank, the pressure control valve opens and allows the HC vapor to flow out of the tank and into the charcoal canister. The purge strategy:

-not operated under cold engine conditions
-not operated at idle
-operates after engine is warm
-operates after engine has been running for a specific period of time
-operates only above a programmed road speed
-operates only above a programmed throttle opening

Can't state with certainty, but I would assume that as throttle opening increases, the pulse width duty cycle will be increased. You could verify that by looking at the sample data log.

All this comes out of the factory manual (I referenced the 94 version, but I'm sure it's the same in 95). Download the copy from Gary's link on Firebird Nation. EVAP system description is in Volume 2 of 2, page 6E3-C3-1.

The consequence of not operating the purge valve will be a buildup of vapor in the canister, until it vents our of the air tube, increasing vehicle emissions. You will have a fuel smell at the driver's rear fender, and it will enter the passenger compartment if stopped at a light with the window down.

If you feel it is necessary to maintain the EVAP system as functional, I would suggest you have the programmer delete the purge function, since you will have to have the LS1 PCM programmed for your LT1/24X application anyway. Incorporate a manual switch to open the purge valve, and only use it briefly when you start to notice fuel odor at the rear of the vehicle. The PCM should use the short range fuel corrections to compensate for the flow of air/HC vapor through the purge solenoid.

Originally Posted by Strick

I'll use the solenoid on the tank instead of the one on the manifold. If that doesn't work I'll use the solenoid on the manifold.

Originally Posted by GaryDoug

I guess I didn't make this clear enough. The solenoid on the tank is not to a purge valve; it's to the vent valve. In a regular 98-02 LS1 car, the purge valve is on the engine, like the LT1 years.

Originally Posted by drptop70ss

So how to operate this system automatically and NOT using the PCM? In my case I am using the 24x system, LS1 PCM, but not the LS1 gas tank, so there are missing EVAP pieces..and so the EVAP has been programmed out of the PCM.
I want to use the 95 EVAP system but want to control the system like a non computer controlled car, and I think they used a thermal vacuum switch that opened once the car was at temp, that way there is no lean idle issue. Would having the vacuum being pulled all the time be a problem?