In this article, we will talk about the electronic
management of the Mercedes MR engine and one
of its most common failures.
In this PLD injection system (pump, pipe and
injector), a failure in one of the cylinder banks is very common. This failure
can be related to the control unit but, before reaching such conclusion, it is
important to perform several checkings.
MR systems are installed
in Mercedes trucks, in models Actros, Axor, Atego, Econic, Unimog, etc.,
in Buses and even in Off-Highway vehicles and stationary engines. The control
unit of these systems manages the activation of the unit pumps from all the
cylinders in two banks:
- In 4-cylinder engines (inline engines OM 904/924 LA). Bank 1 is made up of unit pumps 1 and 2, and unit pumps 3 and 4 form bank 2.
Inline 4-cylinder engine
- In 6-cylinder engines, in the two variants installed by Mercedes (inline engines 0M 906/926 LA and V engines OM 501/541 LA), bank 1 is formed by unit pumps 1, 2 and 3 and bank 2 is formed by unit pumps 4, 5 and 6.
Inline 6-cylinder engine
V 6-cylinder engine
- In V 8-cylinder engines (engines OM502/542 LA), bank 1 is made up of unit pumps 1, 3, 7 and 8 and bank 2 is formed by unit pumps 2, 4, 5 and 6.
V 8-cylinder engine
o
With Jaltest, perform a
compression test to confirm there are not mechanical problems in the affected
cylinders.
o
With the help of the wiring diagram provided by the diagnosis device,
check the conditions of the electrical installation from the MR control unit to
the damaged unit pumps.
o
Verify the resistance value of the coils from the
affected pumps. In this case, Jaltest also provides
additional information about the resistance values that such coils should have.
From our Technical Assistance Department in Cojali, and with the
experience of its members, it has been confirmed that, if after following the
steps described before, no failures have been found, the MR
control unit has to be checked and repaired.
MR
control unit
Cojali has a highly
qualified professional team in the Electronics department to
deal with this kind of repairs in just 24 hours. Thanks to the reliability of
such repair works, warranties of up to 1 year can be offered in the repair of
this type of MR control units.
Damián Muñoz
Technical Assistance Department
Hie,Iam Godfrey and I'm experiencing the same problem on om906 engine,when i start the vehicle there is a misfire in bank one,cylinders 1,2,3 but after running for about 10 minutes cylinder 2 and 3 start to work abit reducing the misfire but cylinder one is dead from what I have seen I think it's the MR that has the fault
ReplyDeleteYeah may be
ReplyDeleteMine does the same
ReplyDeleteI need Mr complete fault codes
ReplyDeleteDoes atego has star point for diagnosis, I can find were it was, I old help me out
ReplyDeleteWhat can be the cause of miss firing in the three injection unit
ReplyDeleteWhat can be the cause of miss firing in the three injection unit
ReplyDeleteMy Atego 1823 is misfiring and has no power...what may be the cause?
ReplyDeleteHi, I have a fault MR 0684,what is that?
ReplyDeleteHi i have a v6 misfir8ng when starting up dine all the injectors and done a diagnostic test it tells me error4806 fuel solenoid on valvebank 1 short circuit what can i do
ReplyDeleteHi Is this also applicable for Citaro OM906HLA? we have increase failure of MR fault code with 101 and 104. please advise
ReplyDeleteI same problem with Actros mp1, when the engine is warm its misfiring, please help me out.
ReplyDeleteWhen the engine is warm, misfiring starts, please what could be the problem?
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