I bought a 1988 560SL in 2011 with 134k miles that now has 147k miles. It was well-maintained, but I just replaced the factory fuel filter last year - my Mercedes-only mechanic said it still had some of the "goo" spray on it from when it was shipped from Germany. Regardless, while it always starts right up, even after storing it for 6 months, it occasionally would not start if I tried to start it again shortly after shutting it down at operating temperature. I just thought I was flooding it and would wait a while, then try again and it always started again. However, after about a 125-mile drive yesterday, which included two stops, I got home and shut it off in the driveway, then went back to move it and it wouldn't start. Turns over fine and fires just a little bit at the initial turn-over, but won't keep running. When I took off the air cleaner to vent it, that didn't help, but I found it would fire if I splashed a little fuel in the intake, but only until the fuel was gone. I know I need fuel and spark, and that I have the spark if I manually add a little fuel, but is there a good way to confirm the fuel pump is the problem, versus an electrical problem not powering the pump?