George993

2000 E320 wagon 185k miles. A few days ago turning the ignition key produced no click/no engine turning. Checked the ignition switch with a scanner - no errors, start signal given. The 10A fuse which controls the little fan for cooling the engine ECU/electronics is blown. I replace the fuse, the car starts and runs ok. I try to start the second time - fuse blown again. So I replace the little fan and now the fuse does not blow.

But the car still does not start, the starter is clicking, engaging but stops after the engine rotates by a few degrees. I check the starter relay just in case, try the relay from another good car, all good. I try a good battery from another car disconnecting the old one just in case it has some internal fault, nothing changes.

So I replace the starter, nothing changes.

Looks like even with a strong battery the result is the same as with an almost dead battery - lights dim, voltage drops, the starter does not have enough power to turn the engine past a few degrees. The starter's 40A fuse does not seem to go to +12V, or maybe it goes for so short that the voltmeter only registers a few volts.

Is something shorting? Where? Is that starter control board with 40A fuse busted and if so how to test it? Any suggestions? Thanks!!!

Badluck

Howdy, can you rotate the engine manually? only rotate correct direction, difficult to rotate if you have a fan mounted on your water pump. Can you remove your serpentine belt and then turn the engine by hand???

bbirdwell

Going from memory here...search the internet first; there is an MB bulletin stating you should apply grease (Lithium? Very small amount!) to the flywheel gear teeth. Seems too much friction would cause the Motor Electronics to detect a starter fault and shut down the start process before the engine could start. The other MB bulletin had to do with replacing a starter circuit 10-amp fuse with a 15-amp fuse as the smaller fuse would blow too easily. I'm in the middle of a bottle of very good red wine so please search and do not use this post as gospel!

To quote the X-Files, "The truth is out there".

George993

Problem solved - turns out the little fan which cools the ECU stopped working and it took down the K40 relay module with it. After replacing both the fan and the K40 unit everything is working fine. But it was a bit hard to troubleshoot and replacing the starter was totally unnecessary. Oh well, lesson learnt. A good troubleshoot is to short the starter relay - it causes the starter to turn demonstrating that the starter is fine, and the problem is with the electronics which turn it off

Thanks to all who replied with help.