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D6-8U improper idle

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2 months 1 day ago #239721 by Pete P
D6-8U improper idle was created by Pete P
Stumped a bit by my D6-8U.  She starts and runs fine, hits nice and hard on all 6 cylinders under load but when at a slow idle she'll slow down too much (maybe half what it should be) and then 'catch' herself and go back to normal idle -- except for sometimes and then she'll stall.  If I open the throttle just a little (maybe 1/8 throttle) she's fine and keeps a steady idle.

I changed the fuel filters, which were horrible, cleaned the filter housing, bled the system and it's better but not corrected. Ran her skidding logs for about 8 hrs and no change, positive or negative.   I was thinking an injector may be having issues but it hits perfectly on all six under load and is fine idling at even a slightly advanced throttle setting.   

Thoughts?  

Thanks in advance,

Pete P. 
Harborcreek, Penna. 

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2 months 1 day ago #239723 by Old Magnet
Replied by Old Magnet on topic D6-8U improper idle
What rpm do you have the idle set to?
What your describing sounds more like worn governor parts.

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2 months 1 day ago #239725 by Pete P
Replied by Pete P on topic D6-8U improper idle
Not sure on the low idle setting -- I've never messed with it and the machine does not have a tach. By ear it might be 600? 700? not real fast but in summer, once the engine is hot she would putter along at dead slow idle for hours.

I've never rebuilt a governor either -- any idea how bad parts are to get?

Thanks

Pete P.

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2 months 1 day ago #239726 by Old Magnet
Replied by Old Magnet on topic D6-8U improper idle
Low idle is 550 RPM
I've sort of lost track of governor parts but what is available from Cat is expensive and I don't think governor springs are available any more.

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2 months 1 day ago #239732 by Ray54
Replied by Ray54 on topic D6-8U improper idle
The Cat way to check RPM is at the hour meter with a hand held tach. No idea if one of the new electronic one would work off the little stub. But the hour meter is running half speed of engine RPM,

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2 months 19 hours ago #239741 by trainzkid88
Replied by trainzkid88 on topic D6-8U improper idle
optical tachs are not expensive if you can see the crank pulley you can possibly place a bit of the reflective tape on there and get a reading. abw tools put out one and there's a couple of others almost identical. from memory around 100 bucks

we used a optical tach when we were having govenor issues on a southern cross model yb we had fun getting the right sort of pressure spring to make her run smoothly without surging.

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1 month 2 weeks ago #240091 by TractorDanD2
Replied by TractorDanD2 on topic D6-8U improper idle
Hi, How's the engine oil pressure under load and at idle? Both cold and hot! The pump could be bleeding some oil pressure internally around the safety for the fuel rack. How's the engine oil? Any signs of fuel dilution ? Cheers
Dan

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1 month 2 weeks ago #240096 by kracked1
Replied by kracked1 on topic D6-8U improper idle
Turn the idle up a little. Its very easy to do. There is a half moon cover on top of the governor housing. Remove the cover and the screw twords the front of the machine is low idle. Screw it counter clockwise until it idles smooth at the speed you like. Every time you turn the screw you need to raise the throttle and bring back to idle. The cover locks the screw when you are done.

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1 month 2 weeks ago #240101 by Rome K/G
Replied by Rome K/G on topic D6-8U improper idle

Hi, How's the engine oil pressure under load and at idle? Both cold and hot! The pump could be bleeding some oil pressure internally around the safety for the fuel rack. How's the engine oil? Any signs of fuel dilution ? Cheers
Dan
D318 Dozer engines dont have an oil controlled governor.
 

The following user(s) said Thank You: kracked1

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1 month 2 weeks ago #240169 by TractorDanD2
Replied by TractorDanD2 on topic D6-8U improper idle
I apologize for that. I got the serial number prefix mixed up. Dan

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