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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Old 11-27-2013
Mechsmith
 
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Diesel overview

I have been working on agricultural equipment for many years. Hopefully some of my experience (s) will help.

A diesel is compression ignition. This means that the temperature generated by the piston coming up must be high enough to light the kerosene. Cranking speed must be fast enough so that the cylinder doesn't cool before it fires.
Good battery, cables,and starter and oil viscosity are important.

Compression must be high enough so that the heat in the cylinder will light it.
Valves, rings and head gaskets are important here. Minimum of about 600 psi. Most are much higher.

The injection pump puts a tiny amount of fuel in the cylinder at very nearly the top of the stroke. This is atomized by the injector at pressures of up to about 2400 psi.

Basically in smaller diesels there are two types of compression chambers. (the space atop the piston) Direct injection-- in which the fuel is injected directly atop the piston (or thereabouts) Semi-direct injection in which the fuel is injected into a "pre combustion" chamber connected by a small passage to the main combustion chamber.

The direct injection type can usually use a starting fluid (ether) This is usually factory installed with a control from the operators station. I have seen them on John Deere, International, and Fiats. But some direct injections have glow plugs.

The glow plugs are also several types. In semi-direct injection they are simple heating elements that keeps the fuel vaporized til it fires. The fuel sprays onto it. Now a days they are usually on a temperature controlled timer, but I have seen a "Push to heat" button on some. Sometimes these are in series so if one goes out they all do. Not good. (International; English)


In direct ignition you could have an electric heater that warms up the intake manifold with an electric coil. Perhaps even two of them. (Caterpillar;Gehl Kubota.)

OR you could have an electrical heat element that actually boils and then sets the fuel on fire in the intake manifold. This valve-element combination works a lot like the battery starter on the "Kero-Sun room heaters. When you press the button the element gets hot and passes fuel over it which then lights and warms things up. (David Brown and Case; English and Zetor and Long from eastern Europe.) These tend to put out a gray smoke while cranking (actually vapor) just before it starts.

Basically this is how those systems are supposed to work.

NEVER use a starting fluid on a diesel that has an electrical pre heater. If you are lucky you will merely lose the skin on your hand. Sometimes it will break off the starter but if your diesel was equipped with an ether start go ahead and use it. It will do no harm if it was designed for it.

There are several kinds of engine warmers available. One is magnetically attached to the oil pan. A tank type can go into any fittings that will circulate through 5/8" or 3/4". another fits into the freeze plug holes. another into a radiator hose. Worst thing is (to date) I have only seen 120 volt types.

Knowing how its supposed to work is the first step in figgering out why it doesn't.
ericirvine, rikhall and casioqv like this.
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Old 11-28-2013
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Re: Diesel overview

Thanks for the post. Nice overview!
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