Cat D6 Idle Question

ACEd · Dec 14, 2013

I have an older D6 9U that starts and runs good except when you idle it down. At half to full throttle it seems fine, but if you drop down to idle while waiting, RPM varies up and down with puffs of white smoke with about a 3 to 5 second cycle repeat. In regular use it does not use oil to any significant degree, but I've only recently noticed the idle issue. Any suggestions welcomed.

Thanks Ed

Billy NY · Dec 14, 2013

Wild guess, its fuel system related, white smoke is uncombusted fuel, first thing I would think of is injector nozzle, and the fine atmomization/spray pattern.

Does any of the cylinders miss under load ?

Has it sat a long time in the past, something in the injector pump system, like in the rack sticking ?

Wild guess, someone will know more about that 6 cylinder fuel system than I, the little I do know is more than dangerous LOL !

MMEd · Dec 14, 2013

Runs great under load - which is what has me stumped - is there a difference in idle fuel circuit or ???

dpendzic · Dec 14, 2013

I would look at transfer pump output pressure--may be too low at idle

Anonymous-0 · Dec 14, 2013

Ed,the white puff is a misfire of one cyl. Get the engine running like that and crack the lines one at a time to find the misfiring cyl. Then swap the fuel nozzle with a good cyl and see what happens. If the puff of white smoke follows the nozzle it's the nozzle if not it's the cyl. The puff is either poor atomizing of the fuel or poor compression. It takes heat to fire the fuel and a hard working engine has more heat and will fire poorer atomized fuel or less compressed air in the cyl.
Later Bob

MMEd · Dec 16, 2013

Thanks - I'll try that - seems to be more prone to do this in colder weather. best, ed

Cat D6 Idle Question

ACEd

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Billy NY

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MMEd

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dpendzic

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Anonymous-0

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MMEd

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