For a couple of days after my car sits unstarted for a week, the starter engages fine but the car will not start until I turn the key on/off several times. When it does not start, the glow plug indicator light does not come on but the aux. fan in front of the radiator DOES come on.

At the lucky turn of the key that does allow the car to start, the glow plug light comes on and the aux. fan does not come on.

I'm pretty sure that something (e.g., a bad relay, sensor, or something) is closing the fuel shutoff valve. I think this something is moisture related since I only see this problem after the car sits for a week or so.

A few more details:

This can happen if the car is hot or cold.

I don't think it's key related as I understand the key-related start-problems did not start until M-B introduced fancy keys in 1998.

After starting, the car runs normally.

Do you guys know what what failed relay, sensor, etc. would cause the glow plug light to not come on, no fuel flow, and the aux. fan to come on?

NOTE: Also posted in diesel discussion

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)