Runaway diesels

VERY LITTLE is ever mentioned about runaway diesel engines, despite the fact that most sailboats have diesel auxiliaries these days. I guess that's because runaways are very rare; but it can be a very frightening experience when it does happen.

It's particularly scary because the engine races out of control and you can't shut it down in the normal way. It will rev up and run out of control until it overheats and seizes or, more likely, starts to disintegrate and throw red-hot pieces of shrapnel at you.

The trouble is that it's not burning diesel fuel. It's firing on its own lubricating oil from leaky seals, an overfilled sump, or badly worn piston rings. It is a very traumatic experience and no amount of fiddling with the throttle or cut-off knob will make any difference, since the injectors are not providing the fuel.

Now you have to remember that a diesel requires three things for combustion: very high compression, fuel, and oxygen.  So one answer to the problem is to cut off the air that supplies the oxygen.  Some engine manufacturers, aware of the possibility of a runaway engine and its potentially disastrous consequences, provide slides or flaps over the air intake that can be brought into action in an emergency.  You can do the same thing by holding a piece of plywood or aluminum sheet against the air intake to close it off, or even a pillow or some substantial piece of cloth — but remember, the suction will be terrific.

The best way I know to stop a runaway is to fire a carbon dioxide fire extinguisher at the air intake. It must be large enough to operate continuously until the engine has come to a dead stop, of course.

It's also possible to stop a runaway by operating a valve lifter, which removes the necessary compression from the cylinders.  But not all engines have valve lifters and in any case most authorities warn you not to try it because the unregulated engine will be spinning so fast by the time you think of it that releasing compression might cause great harm, not only to the engine itself but to you, too.

I should add by way of reassurance that the chances of this happening to you are about the same as your chances of winning the jackpot. But it could happen, and a good sailor should be aware of the possibility. And it would be a good idea to have a carbon dioxide fire extinguisher on board in any case.

Today's Thought

It is questionable if all the mechanical inventions yet made have lightened the day's toil of any human being.
— J. S. Mill, Principles of Political Economy.

Tailpiece

After a hard day's work at a Far East Reconciliation Conference in New York, a group consisting of a South Korean, a Vietnamese, a Burmese, a Japanese, and a Cambodian headed off to a nightclub for relaxation. They were halted by the doorman. "Sorry, gentlemen," he said, "but you can't come in here without a Thai."

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

The Toyota Syndrome

(Stop by here every Monday, Wednesday, and Friday for a new Mainly about Boats column by John Vigor.)

WHILE TOYOTA RECALLS millions of cars to fix a problem with engines racing out of control, the makers of diesel engines for boats are purposefully keeping very mum and looking the other way.

You might be interested to know what’s going through their minds. It’s the fact that it’s possible for most of your engines to develop the Toyota Syndrome, too. And there’s little more frightening than a runaway diesel on a boat.

As is the case with Toyota cars, the problem is comparatively rare. Well, all right, extremely rare. But if it can happen at all, a good skipper like you ought to be aware of the possibility and what to do about it.

The first thing to understand is that a runaway diesel is running on oil, not diesel fuel, so you can wiggle the throttle and pull the stop button all you like and it won’t make any difference. The oil comes from an overfilled sump pan, or a seal that’s no longer doing its job, or oil somehow getting into the air intake.

Your first clue comes when the engine runs faster and faster until it is a bomb ready to explode. It roars and vibrates and tries to blow a piston through the cylinder head with the force of a landmine. None of the usual controls will stop it.

Now, before this happens to you, think about the three basic things a diesel engine needs to operate. It needs fuel. It needs air. And it needs compression, lots of compression. If you can deprive it of any one of these three things, it will cease to run.

Well, there’s not much you can do about the fuel since it’s stealing its own from the engine’s lubrication system, not the fuel tank. As for compression, some engines have little levers that release the compression in the cylinders, but if you release the compression at runaway speeds you’re likely to do serious damage to the engine, and possibly to yourself. Some engines have glow-plugs, and if you unscrew each glow plug you may be able to decompress the engine completely, but at the cost of the plugs being shot out at lightning speed with lethal force.

So we come down to air. Now some engine manufacturers, knowing full well the possibility that their engines might some day suffer the Toyota Syndrome, even before Toyota thought of it, provide metal plates, flaps, or sliding gates that can be moved to cover the air intake and starve the engine of the oxygen it needs to run. Most manufacturers do not.

Nevertheless, you can achieve the same result by blocking your engine’s air intake with a piece of plywood, or plastic, a big towel, or a small cat. (This is, after all, an extreme emergency.)

This could be much more difficult than it sounds. A roaring engine is a very frightening thing to be in close contact with. But there is an easier way to calm the roaring beast. What you need is a carbon-dioxide fire extinguisher. Aim it at the air intake and keep firing until the runaway engine gasps and dies. Which it will, fairly rapidly.

So now all you have to do is: 1. Buy a carbon-dioxide extinguisher, and 2. Find out where to squirt it. It’s probable that your air intake, like mine, is on the aft end of the engine hidden from view, squeezed under the cockpit, and almost inaccessible to a normal-sized human being, certainly one paralyzed with fear.

So get out the manual or make the calls, and be sure you know where your engine sucks in air. Then you can sigh with relief as the Toyota Syndrome becomes just one more item you can scratch off your list of possible boating disasters. Now you have the time to worry about the rest.

Today’s Thought
The misfortunes hardest to bear are those which never come.
— J. R. Lowell, Democracy: Address

Boaters’ Rules of Thumb #16
Bilge pumps. No matter how many electrical or mechanical bilge pumps are installed, you still need at least two manual pumps. One must be accessible from the helm and both must be fitted with easily reached strum boxes perforated with small holes.

Tailpiece
The treasurer of the British Royal Academy at one time was a very polite architect named Sir Edward Maufe.

One evening he arrived late for a dinner. He quietly took his vacant seat, turned to his neighbor, and introduced himself, saying “I’m Maufe.”

The neighbor was astonished. “But you’ve only just arrived,” he said.