Can this really happen?

was wondering if a diesel engined car could really run with a dead electrical system.

Yup! The fuel pump is mechanical, and in those old cars a cable connected to a knob on the dash mechanically shuts off the fuel flow to stop the engine. In newer Mercedes with key-start, a vacuum device worked by a valve (not a switch) on the back of the ignition lock is used. In most brand-X Diesel cars, a dead electrical system will cause an electrical fuel shutoff to close, stopping the engine.

Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201 609-641-3392

The older diesels, once running, require no electrical power whatsoever. Their fuel pump is mechanical, combustion is from their own compression and, finally, if M-B, their shut down is controlled by a vacuum powered bellows that pulls the injection pump's fuel rack to OFF. That's their simple beauty and why they appeal to DIY owners.

Large ship propulsion diesels are typically started with compressed air, some trucks used a compressed air powered starter motor but these truck engines have been replaced by computer controlled engines.

I can't imagine a normal diesel-powered car being able to run with no electrical power, just because the ignition switch must control something (I'm assuming part of the injection pump, even on an engine with a mechanical injection system), and with no power it's just like the ignition switch was turned off.

In the early 70's I was in the Peace Corps in Africa working on a road building project. The first thing to go on all the trucks was the battery, either thru neglect or theft. Every night they'd park one of the dump trucks, (diesel, mostly Fiat and Mercedes, around 10 ton or so) at the top of a slight incline at the depot. The next morning they'd push- start it by hand and then use it to push-start the other diesel trucks, buses, etc. It was quite a sight to see...20 or 30 guys pushing this big truck. They used the one that they had found to be the easiest to start so it really wasn't all that difficult. Woe to the guy who killed the engine before they had started another truck (and AFTER it had rolled down the incline). It was even more of a sight to see them push it back up the incline...

The same applied to a number of the Mercedes diesel cars they had. The fuel pumps and injection pumps were all mechanical so no electrical power at all was needed.

So yes, it is possible...

Modern day diesel engines have electronic controls for emissions. the emissions are controlled by a computer that has maps. When the computer is not powered, the engine will not run.

At least on a Mercedes, the "ignition switch" is actually the "turn on juice to everything that wants it, and spin the starter" switch. Actual run/stop is controlled by a valve in a vac. line that opens/closes with the turning of the key - when the valve is open, vacuum holds the rack in the run position, which feeds the engine fuel. When the valve is closed, the vacuum is killed, and the rack "falls shut" to the off position, cutting off fuel flow to the cylinders. The only reason the engine needs electricity (other than the case of computer-controlled rigs) is to engage the solenoid/spin the starter to get it going to begin with. Once she's spinning, everything is purely mechanical, so you can pull the battery and alternator wires, and she'll keep right on turning until the tank runs dry or the fuel-kill is activated.

In this case, the electrical system is all about running the gadgets and turning the starter. Everything else about it would utterly fail to notice if electricity stopped working tomorrow.

Not only possible, but that was (and in at least some cases, still is) an absolutely flawless supposition.

I've owned 2 240D's with manual transmissions and I live on a good sized hill. If I had only used the car during the day the battery would have been unnecessary.

You guys are forgetting a very important point. How do you preglow the cylinders without electricity.

info.

WAIT A MINUTE where is the starting voltage coming from I thought diesels started from a electrically heated glow plug. I know NOTHING about diesels but, it seems to me, starting an engine with a compression ratio of 400 psi, should be harder than my old 60' Ford Falcon stick, unless there is some sort of piezo electric effect. Are you saying pushing a cold diesel, with no battery, down a sloped driveway would compress the fuel enough for it to combust? getouttahere!

I was told, in life boats they use diesel engines started by hand.

Can anybody confirm that?

Timothy

"Robert Calvert" schreef in bericht news: snipped-for-privacy@corp.supernews.com...

True, Also while in the army (British) I used to hand crank old generator sets 7 & 12.5 Kva, summer time that is, winter time put an old oily rag in the air filter place and set it alight, then crank her good. These did use a pre-compression lever, to relieve the compression of the engine untill you got up to speed and let it go. They usually started with a big black cloud of exhaust and took a few minutes to get up to speed, but they did run for ever. Colin D.

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: > Even though it is true that a diesel has no ignition system, I have always : > assumed that a diesel still used some kind of electrically operated : control : > system for the fuel pump. After all, even diesel cars have what would be : > regarded as an "ignition switch" in a gas powered car. Even though I doubt : > that a modern diesel could run without electrical, I suppose it is : possible : > that older diesels had some kind of mechanical linkage that controlled the : > fuel pump. Any comments? : >

: > Robert : >

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: :

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In the example that the original poster referred to, the engine was already running and then lost an alt belt and subsequently the battery.

My cousin has a generator that uses a small deisel engine. Starts with a hand crank. Has no electrical system. Cute little thing.

D>

Yes, this can happen. In fact, it happened today - the negative terminal cable came loose and off of the battery terminal, and as such I lost all electrical functions - no radio, lights, signals, wipers, NOTHING. But I still had power steering, brakes, and the engine ran without complaint. Scary stuff.

In alt.auto.mercedes Robert Calvert wrote: : After listening to last weeks puzzler, and hearing the answer on Car Talk, I : was wondering if a diesel engined car could really run with a dead : electrical system.

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: Even though it is true that a diesel has no ignition system, I have always : assumed that a diesel still used some kind of electrically operated control : system for the fuel pump. After all, even diesel cars have what would be : regarded as an "ignition switch" in a gas powered car. Even though I doubt : that a modern diesel could run without electrical, I suppose it is possible : that older diesels had some kind of mechanical linkage that controlled the : fuel pump. Any comments?

: Robert

Only some engines have glow plugs. Not all diesels have glow plugs. Takes longer to start in cold weather, but they all run.

Larry In the back yard, under the oak.

I've heard that diesels don't even use glow plugs anymore. I'm not exactly sure what they do, but I think the timing is either advanced or retarded during a cold start.

Robert

of course, for earlier engines. my dad put in a W115 300D engine into a Ford Econoline, the only electrical thing is the starter. 150,000KM so far and no problems

cp

Switching the ignition off would switch the power off, and older diesels have no essential electrical compnonents.

cp

that's different, the actual engine has no need for electronics to function.