An MD80's 'LT CSD OIL PRESS LOW' light illuminated during climb. The CSD was disconnected and because the APU would not start the crew declared an emergency and returned to the departure airport.

Narrative

We were scheduled to fly a leg west. Our original aircraft was taken out of service for a repeated auto throttle problem. After a significant delay; we were rewarded with aircraft. This aircraft also had auto throttle inoperative. Takeoff and climbout were uneventful until we were climbing through FL240 enroute to FL300. Approaching 24;500 FT the 'LT CSD OIL PRESS LOW' amber light kept flickering on and off and then came on steady. While we consulted the QRH; the 'LT GEN OFF' amber light came on. At this point the autopilot kicked off and I requested a descent back to FL240. I shut off the galley power and turned the APU master switch to run and waited 1 minute before starting the APU. The first attempted start was unsuccessful. QRH procedures were followed and LT CSD was disconnected. I requested a turn back towards our departure airport from ATC. We had inoperative auto throttle; the autopilot had disconnected and we were over 133;000 LBS. After the 5 minute cool period we attempted a second APU start which was unsuccessful. Called Dispatch and informed them of our intent to return to our departure airport. Our third and final attempt to start the APU proved unsuccessful. Declared an emergency with ATC and requested as a precaution Airfield Rescue and Fire Fighting equipment to be on the far end of the runway if we needed them. Notified Flight Attendants and made a PA to passengers. Got direct to the arrival. Approaching and landing at 130;000 LBS uneventful. Airfield Rescue and Fire Fighting noted no anomalies or smoke; fire etc; from main landing gear or aircraft. Taxied clear of the runway. Made PA to passengers on taxiway assuring them that the aircraft was ok and that we had an uneventful precautionary landing. Taxied back to gate.