1988 deville starting problems
 

The fan in this car constantly runs and the previous owner installed a switch under the hood to turn this on and off so this does not drain the battery. (???)
However, the car does not start consistently. It jumps when started. The battery is not dead.

Is this a ignition problem?

Alternator problem?

Jumps
 

Do you have the Diagnostic center on that car?? Can you pull the codes.Sounds like it could be a timing issue. If you have the throttle position sensor, that could need adjustment. I'm sure you already know but just in case you don't, when you start the car with the throttle position sensor on a vehicle you shouldn't use any throttle till it fires up. Doing so will throw it out of timing.Are you getting good spark at the plugs??