Part of the normal noises from the engine preparing to start is a "click" from the SOV and a sort of "tok" sound from the fuel rack cycling and releasing.

These sounds may be almost simultaneous but they can be heard if you have the window or door open. I would listen for these sounds each try at starting and if any are absent, you can start to determine why.

Once cranking, the ECU will advance the rack forward slowly until the engine catches and then the rack moves back to an idle position where it's regulated by the ECU. This can be observed if the side cover is removed from the IP.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250