Hey there i currently just got a great condition 1991 deville fleetwood, and everytime the car is off, some strange motor inside the engine starts working, kinda like a compressor, can anyone tell me what it is, we curently disconnected it for now
It's the self leveling suspension compressor. Pumps up some air shocks in the rear until the car sits level. If it's running all the time the system probably has a leak. If it's only running for a few seconds, it's just doing it's job.
Most upper-tier GM cars have SLS. Not sure how the '91 is wired to work. My '87 runs for about 10 seconds after the car has first been started, but I seem to remember a post here about some that operate after the car is shut down. Running for minutes doesn't sound right to me though. You might want to check your owners manual to see how it's supposed to operate.
BTW - is this a front drive Fleetwood? You may be in the wrong section.