OM642 Cranking problem at warm engine
10-04-2020, 02:37 AM
#1
Newbie
Thread Starter
Join Date: Sep 2020
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
W251
OM642 Cranking problem at warm engine
Hi!
W251 is my first modern Mercedes (had W123 10 years ago).
I have problem that nobody knows how to fix and why it's appearing.
When car is cold - engine starting normaly, no smoke etc.
When is hot - turned of hot, and turned on after 5-10 minutes- same.
When I turn off the engine hot and wait 20-30mins starter motor is starting turning the engine, then something is blocking it (the engine) and after half of second it's turning normaly and starting. Sometimes it's not blocking, its turning slower for eg. 2 strokes and then normaly and starting.
Battery was changed by previous owner half of year ago. When I measuring voltage on positive connector under the hood when cranking normaly is falling to 9v, when cranking slower or blocking to 6v and positive connector getting really hot. When engine start after blocking or slower cranking and then I turned it off its starting normaly. There is no smoke from the exhaust (DPF removed).
Starter motor was removed, cleaned and checked by 3 different guys doing only starters and alternators.
Do you have any sugestion what should I check?
W251 is my first modern Mercedes (had W123 10 years ago).
I have problem that nobody knows how to fix and why it's appearing.
When car is cold - engine starting normaly, no smoke etc.
When is hot - turned of hot, and turned on after 5-10 minutes- same.
When I turn off the engine hot and wait 20-30mins starter motor is starting turning the engine, then something is blocking it (the engine) and after half of second it's turning normaly and starting. Sometimes it's not blocking, its turning slower for eg. 2 strokes and then normaly and starting.
Battery was changed by previous owner half of year ago. When I measuring voltage on positive connector under the hood when cranking normaly is falling to 9v, when cranking slower or blocking to 6v and positive connector getting really hot. When engine start after blocking or slower cranking and then I turned it off its starting normaly. There is no smoke from the exhaust (DPF removed).
Starter motor was removed, cleaned and checked by 3 different guys doing only starters and alternators.
Do you have any sugestion what should I check?
