88 260E ANY HELP APPRECIATED

I'm trying to determine if my car stauling problem is the fuel relay or pump/pumps.Stops on me once or twice a week, and take a few turns before it starts up again. I changed the filter and the problem still persists.A mechanic told me a way to check it. When it stalls, put it in park, raise the hood and turn the ignition on, only far enough to hear the pump kick in repriming the fuel line. If you dont hear it trying to pump for a second or two, then the relay is bad, no fire going to the pump. And if you hear it kick in, then its the pump, maybe its sticking. Does this test sound accurate? I will do this test, been 3 days now has'nt happened again yet.Is there a better way to check it, without getting drained by the dealers, wanting to fix everything under the hood? For original question and symptoms see past post on 10-03-05 (88 MERCEDES