Author Topic: Adding Fast Idle? (4104)  (Read 663 times)

Offline Nova Eona

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Adding Fast Idle? (4104)
« on: October 18, 2019, 08:13:50 PM »
Still in the process of familiarizing myself with the new 4104, but one thing I've found it does not seem to have which I wish it did is a fast idle setting.  I think I've heard these came from the factory with a hand throttle which doubled as a fast idle and cruise control, but this particular bus has been changed out to an air operated throttle, so I'm not sure if that remains an option.  Anyone have any advice or opinions on adding a fast idle option?  Am I best off looking at an aftermarket cruise control system?  If so, which one?  Thanks all.

Offline chessie4905

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Re: Adding Fast Idle? (4104)
« Reply #1 on: October 19, 2019, 04:02:46 AM »
You could spend to add the Cruise King or King Cruise control. Cruise King is new name since it was bought out. It comes with adjustable fast idle, is somewhat spendy new, but new owner is good for any assistance. I recently had an issue with an installation of an old unit. Cruise is great to have even on an 4104 on the level, lol. Hand throttle sucks. You can't  keep fast idle constant. It creeps up as engine warms up.
GMC h8h 649#028 (4905)
Pennsylvania-central

Offline Geoff

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Re: Adding Fast Idle? (4104)
« Reply #2 on: October 21, 2019, 02:18:55 PM »
Fast idle on an air controlled throttle wouldn't be hard..  You need to find a 70's-80's bus that has an air throttle with fast idle, it will be a V71 or V92.  it is mounted on an aluminum plate that bolts to the top of the governor.

It has a fast idle plunger and another plunger controlled by an electric over air Skinner valve.  You just adapt it to your engine.  However, if you are not familiar with working on Detroits this may may be a daunting task.

--Geoff
Geoff
'82 RTS AZ

Offline TomC

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Re: Adding Fast Idle? (4104)
« Reply #3 on: October 21, 2019, 04:26:07 PM »
I have a King Cruise on my air throttle. Because I have a V730, I wanted the throttle depressed with the cruise control since the throttle modulator on the transmission works off the air throttle. Hence, I simply mounted an extension piece of metal with a bigger than the cable hole (so it would slide through when I'm using the pedal). I mounted the control on the right side of the dash inside the cabinet facing down with the cable looping under the bus coming up to pull down on the accelerator. Works well and is pretty accurate. I can use it as a fast idle also. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline chessie4905

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Re: Adding Fast Idle? (4104)
« Reply #4 on: October 21, 2019, 05:30:46 PM »
I set mine up the same way.
GMC h8h 649#028 (4905)
Pennsylvania-central

Online dtcerrato

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Re: Adding Fast Idle? (4104)
« Reply #5 on: October 21, 2019, 07:23:14 PM »
We have the original mechanical throttle cable and hand throttle cable on our 4104. It works really well through lots of years except for when it gets below freezing. Need to pull and clean & lubricate the hand throttle cable. Just a little PM.  :)
Dan & Sandy
PD4104-129 since 1979

Offline Lin

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Re: Adding Fast Idle? (4104)
« Reply #6 on: October 22, 2019, 10:04:47 AM »
We had fast idle until we installed Jakes.  The Jake buffer switch for fast idle was rather expensive.  I rarely need fast idle, so now I wedge a hiking stick between the pedal and the seat when I do.  It works but takes some adjusting.
You don't have to believe everything you think.

Offline HB of CJ

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Re: Adding Fast Idle? (4104)
« Reply #7 on: October 22, 2019, 01:28:17 PM »
Or ... you could just sit behind the wheel watching the various gages, (or lack thereof) while gently pressing down on the gas pedal while building air.  Once you have established oil and air pressure then begin another fun wild ride with your cool 4104.

But ... how would you then do that required safety check walk around?  It might take two people to do this.  Your trusty co pilot?  Dunno.

Offline Geoff

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Re: Adding Fast Idle? (4104)
« Reply #8 on: October 22, 2019, 02:34:37 PM »
That reminds me that my factory fast idle is run off the accessory (3rd) tank.  So the fast idle only works after 5-10 minutes (60 psi) of slow idle at which point the 3rd air tank is fed air.  I need to move the fast idle to the wet tank with the throttle feed.
Geoff
'82 RTS AZ

Offline richard5933

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Re: Adding Fast Idle? (4104)
« Reply #9 on: October 22, 2019, 02:57:47 PM »
That reminds me that my factory fast idle is run off the accessory (3rd) tank.  So the fast idle only works after 5-10 minutes (60 psi) of slow idle at which point the 3rd air tank is fed air.  I need to move the fast idle to the wet tank with the throttle feed.

Funny - mine is the opposite. The fast idle will work when there is about 20-30 psi. The throttle won't work until I'm above 90 psi, and then it will continue to work even if the pressure drops back to below 90 psi.

It's almost as if they 'wired' each of the air systems just a little differently, depending on the configuration and options installed.
Richard
1974 GMC P8M4108a-125 (Custom Coach "Land Cruiser")
1964 GM PD4106-2412 (Former Bus)
Located in beautiful Wisconsin
KD9GRB

Offline chessie4905

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Re: Adding Fast Idle? (4104)
« Reply #10 on: October 22, 2019, 03:54:23 PM »
Another reason for an onboard standby compressor.
GMC h8h 649#028 (4905)
Pennsylvania-central

Offline Geoff

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Re: Adding Fast Idle? (4104)
« Reply #11 on: October 22, 2019, 04:43:48 PM »
Another reason for an onboard standby compressor.

I've upset many campers in RV parks when I have to let my bus run for 15 minutes before I can leave.  My portable air compressor is louder than the bus engine.
Geoff
'82 RTS AZ

Online dtcerrato

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Re: Adding Fast Idle? (4104)
« Reply #12 on: October 22, 2019, 04:44:39 PM »
Or better yet a SCUBA tank. That's right, a SCUBA tank. Holds over 93 cu ft of air @ over 3500 psi. When dropped down to 100 psi by the first stage of any standard SCUBA regulator there's enough air to run the whole bus down hilling using brakes for a long long time. We're gonna put one in besides the aux. Electric compressor cause we love redundancy... No need to start engine nor aux. compressor with the genny, just a whole lotta air in one small compact cylinder...  8)
Dan & Sandy
PD4104-129 since 1979

Offline chessie4905

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Re: Adding Fast Idle? (4104)
« Reply #13 on: October 22, 2019, 04:45:38 PM »
You can't mount it on the roof!😳
GMC h8h 649#028 (4905)
Pennsylvania-central

Online dtcerrato

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Re: Adding Fast Idle? (4104)
« Reply #14 on: October 22, 2019, 05:55:14 PM »
It would look kinda neat up there!
Dan & Sandy
PD4104-129 since 1979