June 25, 2018, 06:41:43 AM

Author Topic: Fast Idle on MC 9 8V71 engine  (Read 2098 times)

Offline berrybus

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Fast Idle on MC 9 8V71 engine
« on: January 09, 2013, 06:15:59 PM »
We recently put on an air throttle and we relocated the shutoff cylinder.  Do we need to relocate the fast idle cylinder?  We do not have jake brakes. 
I guess my real question is just how important is the Fast Idle? Any suggestions?

Thanks again for any information!
Jim
"No man is a bus."

Offline hargreaves

  • 1987 MCI 102A3
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Re: Fast Idle on MC 9 8V71 engine
« Reply #1 on: January 10, 2013, 02:04:36 PM »
Fast idle is mainly used for over the road A/C. It does help build air faster but thats no biggy.  Cheers Gerry.
now as of Feb 2012 series 50 B400  . Sunshine Coast British Columbia

Offline bevans6

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Re: Fast Idle on MC 9 8V71 engine
« Reply #2 on: January 10, 2013, 02:05:21 PM »
It depends to some degree on where your fast idle cylinder is located.  Mine is part of the buffer screw (I do have jakes so there is also a jake switch in the deal) so it is completely separate from any other control on the governor like shut-down or throttle speed.  If you have it I would leave it.  It's main use is to speed the engine so that the OTR original air conditioning and heating system can run.  They draw too much current for the alternator to supply at low idle.  Without the AC, all I use mine for is to speed up the airing up process from a cold start.

Brian
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Tatamagouche, Nova Scotia

Offline flynbanjo

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Re: Fast Idle on MC 9 8V71 engine
« Reply #3 on: January 10, 2013, 06:05:37 PM »
The fast idle for diesel engines is used to keep the oil pressure up for extended idle times.  If you don't idle the engine for very long then it is not necessary to use.  If you intend to idle the engine for several minutes or longer then it would be necessary. 
Steven
81 MCI MC9
Hudson, Florida

Offline lostagain

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Re: Fast Idle on MC 9 8V71 engine
« Reply #4 on: January 10, 2013, 06:29:40 PM »
Yea, it is kind of nice to see some oil pressure at fast idle. I hate it when I see no pressure at slow idle when hot. I guess there has to be at least 8 psi, or the safety feature would shut it down, but still.

JC
JC
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1977 MC5C, 6V92/HT740

Offline TomC

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Re: Fast Idle on MC 9 8V71 engine
« Reply #5 on: January 10, 2013, 10:24:31 PM »
I took my fast idle out when I put in the Jake brake-chose not to use the very expensive double fast idle/Jake brake switch. I have a King Cruise control that works just fine as a fast idle. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.