Fast Idle?

[dreamchasers]

I am trying to determine how to enable the fast idle mode on my, new to me, Prevost Country Coach. On my American Eagle, I would depress the cruise control 'resume' button and the Cummins idle would increase to around 1000 RPM. I used the feature to let the engine warm up while doing my final walk around before departure. On my maiden voyage of bringing the Prevost coach to Texas, I could not figure out how to enable the fast idle feature on the Allison -Detroit combination. I read through the provided Country Coach instruction manual, but to no avail.

I know this is a very simple question and I promise to make my questions more difficult in the future. HA!

By the way, I read the article on 'suspension system repairs' by Jon. What a great job! I think I will follow his advice of component replacement to solve the 'leans'.

Hector
1995, Prevost 45 XL, Country Coach

[Jon Wehrenberg]

Hector,

To enable the fast idle you need to be in neutral and the parking brake needs to be on. If that does not do it something is open in the circuit.

If you are going to follow the article on the suspension repairs use your coach for a while and see how things work. Just before Branson for the first time since I owned my coach (3 years) it decided to lean. It was a single incident because it hasn't leaned since. I'm still going to go through it this winter just because everything else under it is new except the valves.

The hardest part of solving a coach problem is not knowing the history. If you have the maintenance records you have a starting point. Without the records you need to create a starting point, so that is why I suggest getting to know the coach before you dive right in. You may fix something that ain't broke.

[truk4u]

Hector,

My previous Marathon and current Country Coach has a button on the console next to your left arm marked "idle". Not sure about your vinatage, but others may jump in here.

[dalej]

Mine is left of the steer console by my left knee. Fast Idle is the far left of the four buttons, two stage jake is next

[Ray Davis]

My '93 Country Coach had the idle button on the left side near the jake brake and cruise control buttons. As I remember it was about third button down on the left hand row of buttons, and would be labled something like Idle.

You do have to be in neutral for sure, and probably the parking brake on as Jon mentioned.


Ray

[rickdesilva]

mine is on the left side dash....it has a 'bunny rabbit" on the toggle switch

[Jim_Scoggins]

parking brake on
tranny in neutral
cruise control on/set

[Ray Davis]

parking brake on
tranny in neutral
cruise control on/set

It's interesting that a couple of you have mentioned using the cruise control. I had spoken last month with Nick Hessler and he mentioned that procedure, but it was to check the cruise control. I didn't get the impression that it was there in lieu of a fast idle button?

Ray

[garyde]

As Jon said, there should be a idlle relay for fast idle. It should be turned on and off by a switch on your dash. My switch has a rabbit icon.

[Jim_Scoggins]

parking brake on
tranny in neutral
cruise control on/set

Heck guys--bad scoop on my part--the cruise control thing was the way it was done on my last two coaches--one a Detroit and one a Cummins.

What was I thinking? Or not.

Current Coach has a switch jobby as others have inferred.

My coach is still not here with me. Still down at Parliament for the re-do--hope to go get it this month.

Homeless in Virginia.

[Alek&Lucia]

In my 1996 Country Coach the switch is on the left side panel by the window.
Here is the photo, switch is marked RPM.

[dreamchasers]

The latest on the fast idle issue is Country Coach and Prevost are both scratching their heads. The service technician I spoke with today at Country Coach stated that the individual that could assist in this vintage coach was off work today, Friday, and would return Monday. He stated that Monday we should have the answer.

Concerning the picture from Alex&Lucia, my controls looks exactly like yours, except your lower button marked "RPM", is marked "Emergency Engine Override" on my coach. According to the previous owner, the button could be used to override any shutdowns from the DDEC to allow the coach to be moved to a safe location?!!

I will let all know the outcome Monday.

Thanks,

Hector
www.dreamchasers.us

[Ray Davis]

So, you do not have a RPM button in that grouping?

In remembering my CC it had 10 buttons, and the RPM button was
opposite the engine override button, 4th down on the left.

Have you tried the cruise control technique?

[Jon Wehrenberg]

Based on the reported service level others have had with Country Coach did they specify which Monday?

[truk4u]

My last conversation with CC about a minor issue was, "gee, we don't build many of those, we'll get back to you". Hmm, still waiting.. Thanks to Nick, we sorted it out.

[dreamchasers]

The Fast Idle issue remains unsolved and is put on a back burner, at least for now. Country Coach states that the fast idle is activiated by depressing the set (cruise control) button while the coach is stopped and in neutral. This programing to allow the Allison cruise control system to reconize this feature is done at the Country Coach facility. According to Country Coach, if the Allison CPU was disconnected (for body welding or any other reasons) and restarted to its default program, this program change would have been lost.

The resolution is to communicate with the Country Coach's software programming team, then go to an Allison dealer and have this change done.

I think I will wait until I am in Country Coach territory and have them fix this.

Seems so simple, but so complicated.


Thanks for everybody's input.

Hector

[Jon Wehrenberg]

I don't think that the fast idle is a critical issue on a coach that does not have OTR air.

When an OTR air equipped coach is idling, the alternator does not seem to put out enough juice to keep the batteries charged due to the load from the AC system motors. Since there is likely no OTR on your coach there is really no need to let it idle such as in a rest area and even if you did you probably will not discharge your batteries

Fast idle may be important if you are ever required to run the bus engine to stay warm because at low idle the engine may not develop enough heat to warm the coach, such as if a Webasto should fail. Just carry a concrete block to sit on the accelerator pedal.

[truk4u]

Hector,

The bunch as CC has plastic on the brain. I had an 02 and an 04 CC plastic and the fast idle worked via the cruise as you stated. I don't think any of the Prevosts are set up that way, but it seems strange you are missing the button that I believe is a Prevost item.

[MangoMike]

As I recall from one of the seminars at POG IV you always need to use fast idle when idling to (I believe) keep the engine running hotter, not for the Webasto but to burn off excessive fuel in the cylinders.

Mike

[dale farley]

I don't know about the Series 60, but DD told me to never idle the 8V92 for more than one minute without the fast idle engaged. It will accumulate excess oil and fuel. I am pretty sure the Prevost manual said the same thing.

The instructions for my Dodge dually says never slow idle the diesel engine for more than a few minutes, because it will run too cool and will build up carbon deposits on the valves and cylinder walls.

[Jon Wehrenberg]

OK, listen up guys. I'm with Gore on this one......

If you don't need heat or AC why would you let your engine idle? Is it a macho trucker thing?

Dale....idling is not good because of the low temps and the sooting, but where did the minute come from? Did the advisor that told you that ever drive one of these in the real world, and if so has he never been stuck in slow moving traffic?

BTW, a parallel to this is the generator. If you are going to run your generator, load it up and make it work. They will work best under load and unless loaded they also will load up with soot. If you do not often get the chance to load it, on occasion run it with all ACs and the toe space or Webasto heaters on to pull as heavy a load as possible.

[Denny]

Mango

You are correct. At POG IV, someone (I believe the man from Prevost) said to always idle at fast RPM. When starting a cold engine let it slow idle for a few minutes to get the fluids flowing and then kick in fast idle. But always idle at fast idle.

[dale farley]

Jon, I may be wrong, but I do believe my manual said go to fast idle after about a minute. The DD tech did say that the exception would be when sitting in traffic. I think this is more of a general guideline, so that the driver is aware that the 8V92 shouldn't be slow idled for extended periods of time.

[MangoMike]

Nothing better than an undertaker back you up.

Thanks Denny.

mm

[Orren Zook]

You've also got to have enough air up to engage fast idle - 60 or so pounds, I think.

[Denny]

Mango

As I have said before, "I'll be the last to let you down."

[MangoMike]

This is great.

When I die, I might have to be buried in Ohio.

Will a bus conga line fit into the cemetery?
mm

[Jon Wehrenberg]

I was waiting for Denny to try to take credit for that.

He's a rare funeral director because in his case he is the last one to let you down because he actually handles the burial vaults. But as a former burial vault maker who used to provide them to funeral directors we were the last ones to let you down.

Any body else had any weird businesses (that they can talk about in mixed company)?

[win42]

To end the idle argument: Watch your oil pressure guage on your dash at slow idle and then at fast idle. That should tell you your engine is suffering at slow idle.

[Joe Cannarozzi]

I'm with Jon, shut it off.

Harry you are correct about oil pressure at an idle but that preset mark of 1000 or even 900rpm on high idle is way more than necessary for the strait sixs. 100 rpm over idle gets the oil press to jump up, and fuel ain't gettin any cheaper either.

The high idle for us is used for warm-up and sometimes a quick stop to go to the bathroom with the OTR a/c runnin, otherwise I shut it off. We have the 8V but I exercise the same habits with my Truck, it's a strait six.

[ratherBcycling]

This is an old thread but I have an issue on topic so maybe someone can help. 2000 H3 today when I stopped and turned on the fast idle switch, no change to the idle. When I got to the end of my trip I tried again and the high idle was not coming on. I have not done any trouble shooting yet as I am trying to get some suggestions on what it might be. Thanks for any help

[Gil_J]

The emergency brake signal may not be getting to the fast idle circuit.

[ratherBcycling]

So Gil is that something I need to have a shop look at or a simple fix that someone without a lot of mechanical know how can do?

[Gil_J]

I'm currently traveling. When I return I can look at the electrical drawings to see if there's any simply maintenance action if you'd like. Ultimately, it may need to go to a shop for repair.

[ratherBcycling]

Thanks Safe travels

[Pete]

Make sure you have it in neutral, with the emergency brake pulled up. I know that sounds elementary, but it has happened to me before.

[GoneCrazy]

Make sure you have it in neutral, with the emergency brake pulled up. I know that sounds elementary, but it has happened to me before.
I have stopped before and pulled the parking brake and the fast idle has kicked on. When I looked down at the switch it was left in the ON position. When the parking brake is turned off , the engine cuts down to low idle. There has to be a signal sent from the parking brake to to the fast idle switch or relay somehow.
Could someone give Us the short version of how this works please ?

[Gil_J]

Rocky,

As Pete said, the parking/emergency brake must be on and the transmission in neutral for fast idle to work. Depending on model and year, the parking brake also signals the brake lights.

I'm sitting on a plane or I would have already looked up the wiring diagram. BTW, I don't recommend spending the night at an airport. Sadly, there were no hotel rooms left. Travelling with our coach is so much better than what flying has become.

[GoneCrazy]

Rocky,

As Pete said, the parking/emergency brake must be on and the transmission in neutral for fast idle to work. Depending on model and year, the parking brake also signals the brake lights.

I'm sitting on a plane or I would have already looked up the wiring diagram. BTW, I don't recommend spending the night at an airport. Sadly, there were no hotel rooms left. Travelling with our coach is so much better than what flying has become.
Gil,
Yes Sir I understand how the switch and parking brake work with the high idle. I was just sharing how My experience of forgetting to turn off the paddle switch and dis-engaging the parking brake will bring it back down to low idle. A good safety feature IMO. I was wondering how it is all tied together I guess You would say. Like all Electric via a common relay, Or electric and air ? The DDEC is probbably in the mix too maybe ? Mine is working fine now. Just trying to understand the path of it all while the subject was at hand.
Airports are the worst anymore.

[Donnie Myers]

So it is working now? I posted some wiring diagrams for you on Face Book....

[Gil_J]

Here you go.

On page 5.1, lower or far right side of the drawing shows the fast idle circuit.

I can see that Relay 7 is energized when the Fast idle switch is on which completes the circuit from the transmission neutral switch and the parking brake switch.

Once Relay 7 is energized RS1 and RS2 simulate changing the Trottle position sensor such that it will run at 1,000 rpm.

If Relay 7 is not energizing when the parking brake is on, the transmission is in nuetral, and the fast idle switch is on:

With the parking brake on and the Fast Idle switch on, you should 24V on Pin 86 or R7. If you don't find it there, check at pin 2B on the Fast Idle switch. If not there, check Fuse 7 and the parking brake pressure switch.

With the transmission in Neutral, pin 85 on relay 7 should have a ground. If not check the VIMN relay for the transmission.

If Relay 7 is energizing, check RS1 and RS2 and their connection to the trottle position switch.

14655
14656
14657

[Gil_J]

Based on your brake light not working, check fuse 7 and the parking brake switch.

[ratherBcycling]

Gil, thank you for your time on this. I am going to take it to someone. Donnie helped me troubleshoot quite a bit more and now on the dash I am not getting the “P” that the parking brake is on even though I am in neutral and the brake is pulled up. The red indicator light on the leveling system is illuminating “not in Park” when I try to level. Thank you I really do appreciate your time. I told Donnie I wish I knew 1/10th of what you guys did.

[Gil_J]

George,

If you can use a multimeter, you can probably identify the problem. Too bad I didn't live closer or I'd help you out.

[Russ]

We recently had the fast idle stop working for no apparent reason and I finally got back to investigating it after completing the bedroom re do. As Gil mentioned relay 7 (in our case on the old XL, r 77) is where to start looking. According to the electrical drwgs relay 77 is in the fast idle circuit but it was not found in the front or aft junction box leaving me scratching. Eventually I located it under the dash right side in our case, seems like there ar many configurations. Swapped it out and fast idle works perfectly. Another step up the learning/confidence curve accomplished. Thanks again to those responding and helping out others.