PeachParts Mercedes-Benz Forum - View Single Post - Why do some diesels have glowplugs and some not?

Shorebilly · #6 02-03-2007, 06:27 AM

Quote:

Originally Posted by Brian Carlton

All of the 2 cycle Detroits that I'm familiar with never had any glow system. But, they wouldn't start below 32F. without ether unless they were brand spanking new.

I believe the need for glow plugs is mandatory on an IDI diesel due to the very cold environment of the prechamber. A DI diesel has an even chance of starting without glow plugs, but, it's no certainty on any of them when it gets really cold. Ether is the mode of choice to get them going and it doesn't appear to have any negative consequences if used judiciously.

The OM617 type of injection uses a pre-combustion chamber (Indirect Injection).....

The injector does not spray a pattern as most do...instead it "spritzes" a straight stream....

The stream of fuel oil is designed to hit a little ball within the pre-combustion chamber....

This little ball is also designed to retain heat when the engine is running....

The straight shot of fuel oil is vaporized upon contact with the HOT little ball......

The pencil type of glow plug heats this little ball...unsure as to how the older loop style work, for certain....

So when the engine is cold, the glow plug heats the little ball (initially), the fuel is squirted onto the ball, and vaporized.....and combustion occurs when the compression rises to it's ignition point.....after the engine is running the heat of combustion maintains the little ball temperature.....

SB

Note: I think (note think!) that the reason we get the nailing issue is because a piece of carbon (or other trash) causes a portion of the injected fuel to miss the little ball....and to ignite further into the combustion chamber.....and at a slightly later time.....