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With a diesel engine and constant speed governor , does a diesel with a constant speed governor start the engine at wot

Clarify please

Bertrrr said:

Clarify please

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Does adjusting the throttle while cranking make a engine start better ?

In my experience I would say no, I have been around a good number of farm tractor diesels we had to do winter starts both with heaters and cold start with and without glow plugs. It scares me to have the throttle anymore than 5-10% if any during start up. To get that momentary rev-up clattering before you back it off scares me. I do have Kubota diesels on a Grasshopper and a Bobcat Skid loader. Both of those I start with throttle in idle position, above 40 dg. and below 40dg. I either use pre-heat glow plugs or block heaters to bring them up to smooth starting temperature, In my opinion idle starts using some sort of pre-heat/block heat below 50 dg. helps extend diesel life.

If it spins over good and smoke is coming out of the exhaust, you're getting fuel to the combustion chamber, if you need starting fluid to make it fire all the time you may have a compression problem

BWH said:

In my experience I would say no, I have been around a good number of farm tractor diesels we had to do winter starts both with heaters and cold start with and without glow plugs. It scares me to have the throttle anymore than 5-10% if any during start up. To get that momentary rev-up clattering before you back it off scares me. I do have Kubota diesels on a Grasshopper and a Bobcat Skid loader. Both of those I start with throttle in idle position, above 40 dg. and below 40dg. I either use pre-heat glow plugs or block heaters to bring them up to smooth starting temperature, In my opinion idle starts using some sort of pre-heat/block heat below 50 dg. helps extend diesel life.

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I agree with your assessment. Have a Kubota D902 in a Ditch Witch Mini skid that is a pain to start cold below 40 degrees. I take that back. Fires easily with glow plug but because of the hydraulics kills the engine. The Kubota owners manual says to start at half throttle, which I hate. Below 30 forget about it. Come back when it is warmer. You can get it started with multiple crank cycles and lots of white smoke.

Gas engines are at WOT at cranking RPM . Is a diesel the same ?

SeniorCitizen said:

Gas engines are at WOT at cranking RPM . Is a diesel the same ?

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Many small petrol engines, on things like mowers, usually require choke to be applied by moving the throttle lever past the max rpm position - this is the main reason why they go to WOT at start.
There is another factor - the governor moves to WOT when the engine is stopped. The governor will react instantly to return the engine to the governed rpm BUT if the throttle spring is in the max rpm position it will remain at max rpm, until the operator reduces throttle. REDUCE throttle, to fast idle, immediately after start.

Larger engines often have a separate choke - with these it is best to have no/minimal throttle at start - on start up, slowly reduce choke, while slightly increasing throttle, to prevent the engine stalling.

With the exception of some generator & pump installations (where throttle is fixed open to operating RPM) diesel engines should be started at or slightly above idle. In most (older type) installations there will be a pre start sequenced, usually involving some sort of fuel heating system (eg glow plugs).

NOTE:
It is not good for any engine to go from cold start to high rpm, before the engine warms up. This will cause accelerated wear in all sorts of locations.
ALWAYS warm your engine before asking it to go to work (fast idle).
ALWAYS cool (fast to slow idle) your engine after work & before shutting down.