How long will our diesels run without electricity?
 

One of the supposed advantages of our diesels is that the electrical system can fail (alternator quit, battery go dead, whatever) and the engine will keep on running. As long as it's daylight, you can make it home, or so the argument goes.

As I have come to know the various Mercedes diesel models better (thanks to this forum, of course :D) I realize that some of them may not run at all if the electrical system dies. For example, my wife's '96 E300D is fly-by-wire: pressing on the accelerator pedal pulls on a cable that turns a potentiometer. The potentiometer sends a signal to a computer that tells the IP to give the engine more fuel. No electricity, no signals.

If the failure is in the alternator, the battery will provide power for awhile. Using no accessories, anyone know how long the battery might last? Many hours, I would think.

The OM606 was first put in the '95 E300D and had a mechanical throttle. It should run just fine except for the idle system, which is part of the EDS "electronic diesel system" and smog equipment. I suppose the engine will run without it?

What about the W124 diesels? My '87 has EDS on its OM603 engine but is otherwise mechanical. I don't know anything about the later 300D 2.5 engines or the versions in the S-class cars.

Older cars like the W123 and older diesels should be fine. My '85 has the EDS on it but I would think it could be ignored. Will the engine stall if the EDS doesn't work to regulate the idle speed?

Anyway, I was just curious. How about the new cars, Bluetec and all that?

Jeremy

Don't know about the newer models, but I made it home (8 hours) with a fried alternator. Just make sure you're going in the daytime

Bluetec will defiantly give out when there is no power because of is Electric pump that provide constant fuel pressure for injector...

the car will last as long as the reserve capacity of the battery

The 124s? Until you shut it off. All 124s will lose idle control, not a big issue since the A/C compressor won't cut in and drop the idle.

One difference being the later ('91 or '92-up) 124s with the pressure-boost control, it is run by electric solenoids, if the car loses electrical power, it also loses boost.

I ran many hours without power on my way back from Florida 1.5 years ago.....crossed a few states. All because of a dead voltage regulator that I knew was going bad, but thought would be ok for the trip. I was wrong. Now I inspect everything prior to long trips. :o Roadside assistance helped us out though, and it wasn't a big deal....maybe a 2 hour wait/delay. A 617 runs and drives exactly the same with no power as it does with power. :D Minus the radio and gauges.....and so on.....no brake lights or blinkers either.

How long it will last depends on how quickly you notice and cut accessories to save the battery. I lost the alternator in the 93 SD 3.0. The battery couldn't power the turn signals within 5 miles. I don't know if the brake lights were still working at that point. Engine ran fine (converted to pressure actuator) but idle was low.

Sixto
87 300D

Wouldn't it get frightfully hot in the car with the monovalve stuck open and the windows and sunroof closed?

Does the sunroof crank in the trunk open as well as close?

Sixto
87 300D

W115, W116, W126 (80-85) and W123 diesel will run until it is out of fuel.

An OM601/2/3 will do the same, but without electricity to power the EDS it will idle at 500rpm. The idle speed can be manually adjusted to 750rpm if you plan on going electricless for a long time. 1995 OM606 will do the same since it was mechanical.

96+, you are SOL if you don't have 10+ volts.

Not from what I've tried. Turning it backwards will just loosen the nut.

A 123 should be able to keep running until it is out of fuel or you it is turned off. A mechanical vacuum valve next to the Ignition Switch turns the IP off. You only need the electricity for the Starter and Glow Plugs.

When I was in the Army they told us never to leave the Manual Transmissions in gear and when we pulled the Shutoff Handle/Cable out to leave it pulled out in the shutoff position. (And, of course to set the Parking Brake.)
We were told that with the shutoff in the run position and transmission left in gear if another vehicle ran into the back of the Truck and pushed (the Army has a lot of big heavy vehicles/equipment to do the pushing and accidents are common) it that it could start by itself just from being pushed.

Other Diesels have electric shutoff solenoids (like my Volvo) any you may or may not be able to run them a ways before they stop.

Not really.....since the blower doesn't work as well, and the flaps all close because the klima powers off.

Windshield defrost flaps and recirc flaps are open by default, closed in off mode when there's power. There's a good draft at 60 mph.

Sixto
87 300D

Huh....I didn't notice much of a draft.....when it happened to me.

A very good draft, I don't have to use my blower when I'm on the highway. I turn on the A/C knob (there is no compressor to run) and the natural airflow keeps me warm/cool. Its just another one of the many benefits of having manual climate control. :D

For all the complaints about it, the automatic klima works quite well....I just set mine at 22C and forget it, car is always comfortable......