M104 Crank no start.
 

1993 300E with the m104 engine.

Sporadically the engine just wont start. Usually happens after making a short trip down the road then trying to restart minutes later. Can try and crank the vehicle for 5 minutes. Usually have to let the vehicle sit for 5 minutes then it will start.

The vehicle never starts while trying to continually crank it. When it does start it is as if it is starting normal, turn the key and it starts. Any ideas what to check?

Probably a bad OVP
 

I would first suspect a bad OVP (over-voltage protection) relay. A bad OVP will cause many things to happen - a non-starting problem, an idle problem, will cause your ABS and ASR lights to come on, will cause fault codes, etc. Check your OVP for the known bad part number, 000-540-52-45. If that is the part number on you ovp, get the new updated OVP - replacement number 000-540-67-45.

The OVP is behind the black plastic cover on the firewall side of the battery. You shouldn't be able to see it unless you remove the plastic cover.

It is silver (aluminum), has a clear plastic flip top on it, and has a tab on the both side of the canister for securing it to the mounting hole.

well i dont think it is the over voltage relay,i think it is the crank shaft sensor.it is the green cable that goes to the ignition control unit sensor is left rear of engine by (flywheel) tranny

The crank sensor should OHM out at approx 900! Check it when the car will start & then again when it won't!

Also the sensor should generate about 0.5 AMP a/c current with the starter turning if it is good!