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OM603 Idle Speed
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Posted 6/10/2010 10:28 PM
Extreme Veteran

Date registered: Oct 2008
Location: Northeast Texas
Vehicle(s): 1994 G350DT, 1972 Triumph TR6
Posts: 386
OM603 Idle Speed

I normally post on the G Class forum but since there aren't many diesel G's I thought I would ask on this forum.
I am wondering what the idle speed should be on my 94 G350DT with an OM603 engine?
The reason why I am wondering is the fact that it has a loping cold idle (could be several things I know)
The normal idle speed on mine is around 550-600 rpm, I have noticed that if I use the throttle and bump it up just a bit during the loping idle to maybe 650-750 rpm the idle smooths out.
The other reason why I am asking is this, one time last summer and again last weekend during a long hot stretch on the highway (mid to high 90's) the engine died after coming to stop on the exit ramp after getting off of the interstate.
The engine restarts just fine and runs normally after that, the engine is not running hot (stays around 90-100C on my gauge)
It never does this in cooler weather and I can drive around all day long in stop and go traffic during the hottest days without any problem. It has also only done it twice in the 18 months I have owned it and they have both been after several hours of highway driving on a hot day.
I am having some occasional problems with my Klima Relay and the A/C is obviously on when this has happened, is there any type of idle stabilization incorporated in the Klima Relay that might occasionally cause this?

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Posted 8/6/2010 5:12 AM

Date registered: Apr 2006
Location: Cape Town ( deep south )
Vehicle(s): W460 *1, W123 *2, W124
Posts: 1315
Re: OM603 Idle Speed

my OM603 in my W124 also has an irregular idle when cold for a few seconds. I t has electronic idle speed control and I suspect it has something to do with the closed loop control circuit.
When conditions are quite hot ( temp above 30 degC ambient ) the idle speed ramps up to around 2000 rpm. There is a fault in the electronics which buts full electrical siginal onto the injector pump. If you remove this signal when hot idle is back to normal ( however it will battle to idle when cold! )

Seems you also have issues with the electronics idle circuit !
#175635 - in reply to #173436
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Posted 8/22/2010 5:12 PM
New user

Date registered: Aug 2010
Location: Nottingham, England
Vehicle(s): '93 300TD, '88 230TE
Posts: 1

RE: OM603 Idle Speed

my 93 300TD has a 603 with electronic idle system (ELR), (non a/c) now I've sorted the ELR it ticks over at about 650 rpm steady as a rock. Mine had a broken crank sensor AND a duff ELR ECU....this ECU is replaced by klima if you have factory a/c, and possibly by ARA if it has anti-jerk (whatever that is...) The tickover stop should tickover about 550, the ELR holds it at 650and smooths it a lot. Also stops a/c when kickdown is in use, and so forth.
You need a klima test -


looks like it is for your setup, time to get the multimeter out mate!


Edited by balge 8/22/2010 5:15 PM
#176469 - in reply to #173436
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