Gabriel S. wrote:
Is leaving your diesel idling really all that bad? I suspect it isn't. I'll tell you this much, my boat has a Straight 6 Volvo Diesel and I idle that thing all day long when trolling for fish and still no ill effects. I don't know what it is about my car, but even though she lights up on the first crank I still find it harder to start than a gasser, who knows, maybe its the effort required to turn the key on a Benz thats harder, all I can say is that I tend to leave her running when possible.
Prolonged idling a diesel engine is NOT desirable. Mercedes cautioned in the owner's manual of my '60s diesels that if it was anticipated that the engine would be idling for more than 2 minutes, then the engine should be shut down and then restarted. The same is true of today's diesels. The running of diesels at very low loads has many damaging consequences both to the engine and to the environment. There are of course times when idling is necessary, but it should be done with the knowledge that the engine is likely to sustain much more wear/damage than if it were pulling a full load at near maximum speed.
As to your engine being "harder" to start than a gas car - that's largely because it's primarily spark that initiates combustion in a gasoline car while the combustion of a diesel is initiated by compression. A diesel engine must be tight enough to permit the compression to develop and the starter must work more than twice as hard in a Mercedes diesel vs a Mercedes gasoline car because of the greater compression ratio of the diesel.
For whatever reason, compared to other Mercedes diesels, OM601 engines are VERY easy to start in VERY cold weather (most will start on the 1st compression stroke of the first cylinder once the plugs approach 1100 deg. C), OM602s are harder to start and OM603 engines are much harder to start. Most of the OM61x engines (both 4 and 5 cylinder) I've owned fell in with the 602 engines as far a starting ease goes. If you allow them sufficient time to reach maximal glow plug temp, they start on the 2nd or 3rd compression stroke (until temps get down to or below zero F).
I believe that the difference between the 4, 5 and 6 cylinder OM60x engines is because the battery, starter and the wiring capacity (current capacity) for the glow plugs are all the same in these engines. So the available battery power is divided into 4 cylinders for the 601 engine, into 5 cylinders for the 602 engine and into 6 cylinders for the 603 engine. Remember, the voltage drop within the battery and wiring to the plugs dissipate almost 20% of the available power. The voltage drop within the battery (all the same sized batteries in MY cars) and wiring to the plugs is least in the 601 (going to 4 plugs) and most in the 603 (going to 6 plugs). Finally, identical starters and batteries to power them are turning and generating compression in 4, 5 and 6 cylinders every two revolutions resulting in the least load (and fastest cranking speed) for the 4 cylinder engine.
With OM61x engines, it's critical that before temps drop below freezing the valves be checked for sufficient clearance so that there is NO leakage even at the coldest anticipated temperatures. Improperly adjusted valves is the second most common cause of poor/no cold starting reported in Mercedes OM61x or older diesels.
Marshall -- Marshall Booth Ph.D. Ass't Prof. (ret.) Univ of Pittsburgh School of Medicine Department of Pharmacology 1300 BST Pittsburgh PA 15261 USA [EMAIL PROTECTED]
