Re: What makes a tractor hard to start in the cold

Posted by Joe Evans on October 07, 2004 at 05:31:28 from (209.41.233.76):

In Reply to: What makes a tractor hard to start in the cold? posted by Bob Spooner on October 07, 2004 at 05:04:37:

Diesel engines get their ignition from compression. A cold block will 'sink' compression heat into it until enough cranking revolutions generate enough compression heat cycles to overcome this. Thus the use of glow plugs on direct start diesels.

In cold temps, there is a vicious cycle of having to crank the engine a lot to build heat, and at lower temps batteries that are not A-1 don't deliver the cold cranking amps. Add to this cranking torque in cold weather connected auxiliary devices--oil pumps and hydraulic pumps trying to push cold, sluggish oil. Don't forget the drain on the battery's power delivery for cranking when you ask it to also heat up glow plugs.

Diesel fuel cooks-off at roughly 700 deg F. Ether has a lower cook-off temp of about half this allowing the engine to fire way before enough ignition temp is generated through compression for diesel fuel ignition. Glow plugs pre-heat cylinders so that fewer compression cycles are needed for starting. They almost act like spark plugs.

If compression is the ingredient for diesel ingnition, then you can assume on an engine that id balky at starting may have suspect compression from age and wear and/or glow plug problems.

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