I bought a 08 GL320 earlier last year and it has always been slow to turn over. Sometimes it turns over so slow it acts like it wont start but always does. Have had a few times where it cranks too long and times out and have to crank it again (keyless go). Battery is new and connections are good and tight. Today I measured amp draw with my clamp meter and its pulling 395 amps. This seems to high but want to make sure. If it is too high, I assume it is starter replacement time. No way to really check the connections at the starter without removing it, at least no way I can tell. In fact, I can barely see the starter from above, or with it on the lift from below.


Anybody got any tips or instructions on 642 GL starter replacement?

I rechecked it this time with glow plugs disabled. Unfortunately this meter is somewhat hard to read while its cranking but it appeared to be mid 200 amps. I then used my new electronic battery tester connected to the charge points under the hood and it tested the battery as bad and to replace. Used my old school tester as well and it showed low also. I am not going to condemn the starter yet. I have the charger on the car and will check it again tomorrow. The battery is about a year old and figured it was good, but may just replace it anyway since I need batteries for other cars anyway.

I have an om642 in a 06 Jeep GC and had similar issues with sometimes slow cranking and then behaving for a few days and then back to slow again.
First thought was battery as most slow starts were with a cold engine at 4-5deg c here in UK.
After a few weeks of off and on cold starting one morning it was hardly turning over and then burst into life with me thinking I will put my spare battery on later and see if it fixes it, well it didn't and it would not turn over any more … key to relay and power to solenoid all. checked out good so that left starter motor.
Well I removed it and replaced with new I had ready ( on the Jeep its removed from above / support engine and remove engine mount to get starter body out ) the autopsy on the removed stater found that the solenoid functioned ok but the main motors brushes were worn completely out with two being just slivers and the other two about 4mm thick.
These starter motors are very small palm of hand size with the solenoid body nearly a third the size of the motor itself and I could not figure how a motor this size could possibly start an engine this size … well there is a set of reduction gears inside so the motor spins at very high speed and the gears create enough torque needed to turn engine over.
I have read that the om642 needs 200rpm minimum before ecu will fire injectors.

So as above I removed engine mount which was four bolts out of block and then one long bolt and nut in the frame rail supporting side.. the starter was just two 15mm bolts through the bell housing and easy to get to… when refitting engine mount raise the engine up slightly more and fix the mount to block before letting down and securing to chassis as this ensures you do not get mount / block bolts cross threaded… I could not see two of mine and did them by feel , I had no access from underneath as front diff blocks all access although I could have removed wheel arch liner and gone in that way to access it… but the starter is tiny and not at all hard to handle.
On the Jeeps they do have a fault where the solenoid wire corrodes and causes problems at the solenoid connection so do rule that out.

I had a starting problem in my 2009 E320 with OM642. Bought a new starter and all was well. Took the old starter apart. Brushes worn out. Bought new brushes and installed them. Starter is now on the shelf as a spare.

They're not often easy to remove but if you're interested, taking one apart and cleaning it , replacing the brushes and adding a little bit of grease will usually bring them right back t life unless you've been grinding away at it for a year or so, -sometimes- in that case you'll discover it's fried, no worries, just button it back up and exchange it .

Only use BOSCH branded rebuilt starts or expect to come back here complaining again....

The box and the label on it should say 'BOSCH REBUILT' and the part number will end with an X .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better