My 560SL has 40,300 actual miles and is in outstanding mechanical condition--except I am having problems with the fuel delivery system. Twice in the past month the car would not start after having been driven lightly for 30 minutes or so. In both instances, the fuel pump was apparently not getting any power, since I could not hear the normal hum of the pump after the key is turned on.

My independent tech replaced the fuel pump relay after the first incident. It occurred again several days later and he then replaced the fuel pump (only has 1 pump--not 2). Yesterday it happened again, but this time it died at a stop sign while it was idling.

When these events occur, the car actually starts for about a second when the starter is engaged, but immediately dies. What do you think is causing this? Could I have another "bad" relay? I know from looking at the wiring diagram that the CIS-E Control Unit and the Electronic Ignition Control Unit are involved in the fuel delivery function. How likely is it that either of these "budget busters" are the culprit? Thanks for any advice.