Hi all.
My 2000 E320, with 55K miles, has developed a curious problem.
It had stalled on me twice today when coming to a stop. I was able to restart it and drive away after about 10 minutes. After the second stall I got on the highway and drove it for about 30 minutes without any problems. When it stalled the first time I checked the fuel pressure and there was no fuel coming from the valve at the end of the fuel line. I also checked for spark and I didn't seem to hear/see any spark when I pulled off the boot and inserted a screwdriver grounding it against the block. After the second stall I didn't immediately checked the pressure, I tried to start it a few times, waited about 10 minutes and then checked the pressure. This time there was pressure and car started right away.

I did search and found that most people seem to have a problem with the flywheel sensor. Is there a way to test the sensor or should I just replace it as it is not too expensive?
Also, would the lack of fuel pressure after the first stall indicate a faulty fuel pressure regulator / fuel pump / fuel pump relay? If so where is it (the regulator and the relay) and how can I test it/them? The fuel filter may have never been changed on the car. This is the first time I use a different brand of gasoline in the car, might be just a coincidence, or could the attendant have put in lower octane which would cause the knock sensor retard the ignition to the max and hence stall the engine?

Thank you for your help.

Alex