91 LS air sus questions

Im looking at buying a 91 LS as a project and it has factory air and its sitting all the way down right now and the fuel pump needs to be changed so i cant run the car to test it out. I got it to run with some starting fluid so i know the motor is good. My question is when does the air compressor kick on, does it run with just the ignition on or does the motor need to be running for it to kick on and does anyone have a diagram of the system and the electronics fot it?

Hello..

Usually, there is a sensor called a pressure switch. At normal operations for example, the storage tank will be at around 150psi.  Then if it drops down to like 130psi, the compressor will kick in and it will keep running till it reaches back to around 150psi. 

With your situation, it will probably kick in right away filling up the airlines and bags and the storage tank with air till it reaches its PSI setting.  Then it will turn off. 

I hope this helps!

If you find a wiring diagram, you can somewhat bypass the pressure switch (temporary) and run the compressor to fill in the lines/bags/tank with air. You will have to probably power it directly with a 12vdc supply, that way...you can also test it out and see if you have leaks. (use soapy water on and spray on the joints).

Good luck!

The motor needs to be on in order for the compressor to kick on and pump the air. Since there is no storage tank in the factory set up, the air will be pump directly into each of the bag. The pump will stop when the height of the car reaches the factory set level.