Re: [diesel_mercedes] Re: Sub Freezing-- won't start '83 SD

In a word, no. Full throttle with a diesel engine is like closing the choke with a petrol engine. You need more fuel to start a cold engine, no matter the fuel. Petrol engines use a choke, diesel engines use the throttle.

If a diesel engine slows down while cranking, or does not start, with full throttle, no matter the weather, there is something else wrong. Diesels very nearly cannot flood. Flooding would cause a hydraulic lock and you'd have a bent rod faster than you can say "350SD".

What happens with a cold engine is that the cylinders cool the charge too much for an easy start, necessitating more fuel. More fuel reduces the combustion chamber's effective area, thereby increasing the compression, and that increases the temperature enough to allow a start. Glow plugs by and large eliminate the need for increased fuel, but get temperatures low enough (Chicago, 0 degrees now), and both are necessary. I have started many diesels in this cold weather, some which had sat outside for days, and this technique has virtually never failed with a good engine. I have also started Merc diesels in slightly warmer weather without glow plugs by cranking with full throttle. Once there is enough fuel in the chamber to increase compression/temperature, they start.

 

Overall, somehow, this reminds me of the motorcyclist who insisted that counter-steering did not work with HIS bike: apparently the laws of physics weren't installed on HIS bike.

 

Jeff

A little help from our engineers out there:  Does the gasoline engine "pump to the floor . . . floods my cylinders" theory hold true for diesel fuel systems?  Does holding the pedal to the floor cause flooding of the cylinders? Is there any connection between the gas and diesel "pumping the pedal" and "flooding" inthat we are talking two different systems  for firing up and engine?

Someone wrote:
"Reason The pump to the floor does not work. I think it floods my cylinders."

brian

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