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COLD WEATHER DIESEL
When temperatures drop, several things happen that can make a diesel hard to start. First, the oil in the crankcase thickens. At the same time, battery output drops, reducing the number of amps available to crank the engine. The 15W-40 multi-viscosity motor oil, a popular warm weather choice with many diesel owners these days, may become too thick when temperatures go below freezing or plunge to zero or below. Straight 30- or 40-weight oils would definitely be too thick. The increased drag created by the cold oil can reduce cranking speed to the point where the engine may not generate enough cranking compression and/or fuel pressure to light the fire.
One of the first things you should check when diagnosing a "hard to start" complaint, therefore, is the dipstick. If the oil is thick and globby, it may not be the correct viscosity for winter use. Switching to a lighter oil such as a 10W-30 (never anything lighter in a conventional oil!) may be all that's needed to improve cold cranking. Just make sure it is oil rated for diesel engines An even better oil would be a synthetic motor oil.
The next thing that needs to be checked is minimum cranking speed. The rpm needed to light the fire will vary according to the engine brand. If the engine isn't cranking fast enough, check battery charge and condition, as well as the cable connections and the starter's amp draw. Problems in any of these areas can make any engine hard to start. If the battery is low, recharge it and check the output of the charging system, too.
GLOW PLUGS and DIESEL STARTING PROBLEMS
If slow cranking isn't the problem, perhaps there's something wrong with the glow plug system. Most diesels have glow plugs to assist cold starts. The glow plugs are powered by a relay and timer that routes voltage to the plugs for the prescribed number of seconds. When the timer runs out, the relay is supposed to turn off the voltage. But relays sometime stick and continue to feed voltage to the glow plugs causing them to burn out. Many people use them manually and end up also burning them out by keeping them on too long.
Starting A Diesel Generator In Cold Weather
In cold weather fuel does not vaporize very well in the combustion chamber and this makes starting difficult.
Modern diesel engines designed for cold weather use a pre-heater or glow plugs. Glow plugs are heating elements that warm up the air that enters the engine. They work on a timed circuit or are manually activated just before the engine is started. The colder it gets, the longer those glow plugs need to stay on to preheat the combustion chamber for a smooth start.
Using the decompression lever on a diesel engine will open up the exhaust valve and keep it open so you can crank faster. Seconds later you release the valve and the momentum of the engine often results in higher compression and speed necessary for starting under difficult conditions.
Gasoline engines that use a carburetor also suffer from difficult starting on cold weather. The cold air and cold cylinder walls prevent the fuel from vaporizing correctly to permit combustion.
Using Engine Starting Fluid is a very effective method to starting both gas and diesel engines in sub zero temperature.
Starting Fluids are made from Ether and petroleum distillates blended together. This starting fluid has a low freezing point and easily ignites even at temperatures as low as -65 F Many starting fluids have added lubricant and anti-corrosive additives. You can buy a spray-can of it at most gas stations and automotive stores. Use caution, it does not require much and over use often causes engine damage. It will 100% void your warranty and is easy to detect if it has been used.