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?
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started with compressed air, some trucks used a compressed air powered starter motor but these truck engines have been replaced by computer controlled engines.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.
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.
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
Glow-plugs make starting a cold diesel easier, but they *ARE NOT* vital to the process - Case in point: an 80-something F350 diesel that we use for grunt work here on the ranch. Its glow-plugs (and in fact, the entire wiring harness that used to power the glow plugs) are toasted, and have been for years. Result: Y'gotta crank it and crank it and crank it and then crank it some more, and perhaps even crank it a little bit more than that before it fires on the first start of the day, but it runs just fine. Once there's some residual heat in the block/heads from the first run of the day, you can shut it down, and it will restart so quick you'd be left totally clueless about the fact that the glow-plugs don't work.
"Your falcon must have a timing issue" is about all I can say. Gas engines with a stick behind 'em are, in general, kiddy-play to push-start unless the timing is off. As a prime example, my '82 Mazda
626 push-starts in reverse with three feet or less of backwards roll, or in third with about 8-10 feet of forward roll - first time, every time, no sweat at all.
That's *EXACTLY* what's being said. The key is getting the air in the cylinder compressed quickly enough to produce an in-cylinder temperature that's at or above the flash-point of the fuel. Glow-plugs (and the associated wiring/power supply) make the process easier by raising the head/block temperature, which in turn raises the temperature of the air charge in the cylinder, but they *ARE NOT* mandatory. The same effect can be achieved (and in fact, this is specifically recommended in some cases) by playing a blowtorch on the head for a while before trying to start the engine.
Lemme give the old diesel a push to get it rolling down the hill, and I'm gone... :)
Fact: Some heavy equipment with diesel engines, like 2 of the 3 ancient (30s? 40s? 50s? They truly are ancient beasts) dozers our hay grower uses for farming his rice, have *NO* electrical system whatsoever on them. *NOTHING* electrical. They don't have a single wire, no alternator, no generator, no battery, no cord to plug into 110 or 220, or any other kind of electrical stuff on the main engine. They DO have a "pony motor" alongside, which, in this particular case, runs on gas (and as such, has the requisite electrical ignition system to make a spark) and starts by way of pure human power - either hand-crank like an old Model T, or pull-start like a lawn mower, depending on which of the two you're trying to fire up. Neither one has anything that even resembles a glow-plug, although I have seen cases where the exhaust from the pony is routed through galleries in, or ductwork around, the head to perform exactly the same function glow-plugs would serve. To start either one of these two Cats, you start the pony, by either cranking or pulling as needed, get it running happy, pull a lever, and the pony spins the main engine until it fires. Then you crawl down on the track, shut down the pony, and go about the day's work.
Alternatively, there are the "air-start" versions - they start from compressed air supplied by either a pressure tank that they pump up while they're running, or an external air compressor. Again, not a wire, battery, alternator, or glow-plug to be seen anywhere on them.
In summary: With a diesel that isn't computer-controlled, electricity, in any form, is *COMPLETELY* optional. Nothing about them requires anything electrical to be attached for them to run, although having glow-plugs does tend to make starting them for the first time each day a fair bit easier.
I believe youi have the aluminum head, so if you can't find any leaks then you probably have a warped head leaking coolant into the combusion chamber, which burns it out so hot you don't see the moisture in the exhaust fumes. I had a similar problem with a 242 Volvo, I pulled the head off, got a fine tooth flat file, and carefully shaved the high spots off the head with the flat file. (For all you naysayers, this technique will not gouge the surface of the head). Then I put it back together with a new head gasket, tune up and so on and my water usage problem was solved with many, many more miles on the engine.
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?
Only relatively recent diesels with things like computer-controlled injection or HEUI (hydraulically activated electronically-controlled unit injection) need electrical power to run. Many older ones did have an electrical solenoid to hold the fuel supply open, but other than that would run with no electrical power. Most older machinery diesels had a mechanical cable to shut down fuel and could run with absolutely zero electrical power.
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.
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.
Nope, direct injection diesels just have a lot higher compression ratio than prechamber/glow-plug diesels, and can start without aid because the air in the cylinders gets much much hotter just from compression. Sometimes a heater is added in the intake plumbing (eg. Dodge Ram) so that the driver doesn't notice longer crank times at lower temps, but its not really necessary. Just a luxury.
Absolutely no electrical power is needed for a diesel engine to work, as long as there is fuel, air and a way to start the engine. Modern diesel use an electrical pump to transfer fuel to the high pressure injection pump, but it is not really needed. Same goes for control system of the HP pump. Engine, like in a modern pick up, will have a electrical motor to control the fuel HP pump, but it is strictly an accessory, and a replacement for a throttle cable / also an easy way to meet emissions, because it can be controlled by a computer. When you turn off the key on a car, you de-activate a fuel shut off solenoid. Convenient but not necessary for the engine operation.
I used to drive a dumper truck which had a single cylinder diesel engine fed by gravity from fuel tank. You had to crank it relly quickly while keeping a big valve in the head open then suddenly close the valve to allow the thing to work. No electricity anywhere and no fuel pump either.
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