Can this really happen?

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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.
http://cartalk.cars.com/Radio/Show/Audio/200350/RA/s05.ram
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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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 http://www.ditmire.com 609-641-3392
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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started with compressed air, some trucks used a compressed air powered starter motor but these truck engines have been replaced by computer controlled engines.
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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.
--
Robert Hancock Saskatoon, SK, Canada
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Switching the ignition off would switch the power off, and older diesels have no essential electrical compnonents.
cp
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Robert Calvert wrote:

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...
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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.
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that's different, the actual engine has no need for electronics to function.
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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.
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You guys are forgetting a very important point. How do you preglow the cylinders without electricity.
No preglow! No Start!
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wrote:

snipped
In the example that the original poster referred to, the engine was already running and then lost an alt belt and subsequently the battery.
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i have a '85 300sd and it starts fine (maybe a bit rough) with NO glow plugs, I checked.
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My cousin has a generator that uses a small deisel engine. Starts with a hand crank. Has no electrical system. Cute little thing.
Don't forget that early cars started with hand crank, airplane with a turn of the prop and even current lawn mowers have no stored electricity, but generate enough once turning to run, so even if you needed glow plugs, throretically you could push it fast enough to generate enough elecricity to still start it.....
Fred Mertz wrote:

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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.
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I knew one guy who had a diesel bulldozer and, according to him, it used a small bottle of ether to cold start the engine. But do diesels even use glow plugs anymore?
Robert

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Robert Calvert wrote:

Only itty-bitty ones, and not all of those. The whole glow-plug/prechamber design is much less efficient than direct injection and has largely been abandoned.
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Fred Mertz wrote:

Only toy engines have glow-plugs, no real diesels need them because they use direct injection instead of a goofy pre-chamber. You wont find glow-plugs in any truck, bus, front-end loader, locomotive, etc. Not even most of the diesel pickup trucks- The Cummins in the Ram has an intake air heater, but its not necessary. Just makes starting a little easier. I think the Powerstroke is the same way- direct injection, no glow-plugs. The earlier Ford diesel had plugs, as did the gone-and-not-missed GM 6.2/6.5.
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Steve wrote:

I have three diesel farm tractors. One has glow plugs, one has ether injection, and one has an intake tract heater. The latter two also have block heaters. The only one that you can count on starting on really cold days; unless you use the block heaters; is the one with the glow plugs.
Ed
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The GM Duramax engine uses glow plugs with a direct injection system - they're controlled by the ECM, and can also run for a brief period after cold start to help clean up white smoke or rough idle after cold starting.
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I believe my girlfriends new VW TDI has glow plugs, at least there's a preheater idiot light on the dash that I assume is for the plugs.
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