Yesterday my '89 300CE refused to start after shutting engine off for short time. Car started up fine cold after sitting a day but I had to return back home as I forgot to take something. Turned car off for 30 seconds- 1 minute and then went to restart but it just cranked and would not start. I went and wiggled the fuel pump relay and went back to try and it started right back up. How do these things go bad? I hear them causing problems when they get older so I want to replace mine right away. What brand is best? Looks like there are a couple to choose from including Kaehler, Kostal (OEM) and Mercedes.

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1989 300CE