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Author Topic: Tag Axle Low Air indicator light on. Can't reverse  (Read 2743 times)
topfrog007
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« on: February 20, 2012, 11:45:17 AM »

Hi All,

86 MCI 102A3. Was going to take for a quick spin, it's been sitting for a few months while we demo the interior.

Turned on, aired up and noticed the Tag Axle Low Air light illuminated on dash. Went back to check air on them and they both seemed plenty full of air with no audible leaks.

A pin under the accelerator locked into place anytime we put it into reverse, this prevents the peddle from being depressed.

Does anyone know what the problem might be? I read in the archives that there are some drain valves that are meant to drain our moisture from the air system. Could this be the problem? I'm not sure where they are located on my bus.

Thanks!
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #1 on: February 20, 2012, 01:27:16 PM »

Locked throttle pedal in reverse?

What is the temperature? If you don't know where your drains are, all bets are off.

One on each of your 4 air tanks, and the discharge muffler drain inside the rear right side engine access, mounted on the back side of the tag wheel fender.

But, if it is below freezing, what's going to come out?

In the troubleshooting thought process, the fast idle will inhibit the throttle pedal, or some door/kneeling/wheelchair interlock. Did the coach have any of these other features?

The fast idle is air powered on that vintage coach, so air system trouble back there with the tag axles and a wonky high idle circuit might be related.

Note the date on this thread:  http://www.busconversions.com/bbs/index.php?topic=21559.0

Use the search and read a ton about air system maintenance, usually in a thread about brakes sticking, won't air up and similar shrieks for help. Including my name in the search along with some of those other air system type words will help, I seem to be in most of them, the collective wisdom will be nearby...

happy coaching!
buswarrior

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topfrog007
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« Reply #2 on: February 21, 2012, 10:42:36 PM »

Hi Buswarrior,

Thanks for the response.

It has been in between 45 and 75 degrees the past few weeks here so freezing isnt an issue. Although it may have gotten down to 25ish once or twice this winter. This is the first time we've tried to move it in a few months. It has been turned on and idled for a few minutes once or twice a month.

I did have the fast Idle on, but thought I tried it with it off too. I will have to check on that.

If I shift into any of the forward gears the pin retracts and allows me to press the peddle, the second I shift into reverse the pin comes out and locks the peddle from being depressed.

I know of one air drain beneath the drivers chair/electrical panel and the muffler drain. I didn't know they had/could have moisture in them. Should I be draining these frequently?
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #3 on: February 22, 2012, 06:49:45 AM »

Idling a couple times a month is a waste of time. The engine will never come up to operating temp just sitting there, it must be driven to get it hot. You are better off just not starting it if you are not going to drive it a little bit. Especially with the DD 2 stroke, you are better off just running it long enough to build air, then put it in gear and drive it like you stole it.
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« Reply #4 on: February 22, 2012, 05:55:43 PM »

This pin under the accelerator.

Can you see it? What activates it? What powers it? Can you disable it, taking precautions for unintended movement, and see if it will back up?

Has anyone else been witness to this pin in their coach?

happy coaching!
buswarrior
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Ed Hackenbruch
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« Reply #5 on: February 22, 2012, 06:12:02 PM »

As Thomas said, if you fire it up, drive it for a while. When you shut it down, drain the tanks.
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« Reply #6 on: February 22, 2012, 06:27:39 PM »

I'm not sure how short idling the engine has made this problem.

Let's start another thread about the debate about what a busnut should or should not do with the engine during a time of static storage/during conversion while the coach is not able to go down the road.

From the sounds of it, we've got a busnut with some interesting and rare throttle inhibit, or a neat way of a newbie describing his experiential learning as he goes along, no matter, a thread that will help him, and us, and those who follow.

Not often that we read of strange and new thoughts or hardware these days.

topfrog, are there any of those other questions in my other post apply to your coach?

happy coaching!
buswarrior
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Scott Bennett
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« Reply #7 on: February 22, 2012, 06:37:43 PM »

pics pics pics....would SO be helpful...  Grin
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Scott & Heather
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« Reply #8 on: February 22, 2012, 06:47:25 PM »

yes, digital pictures, close and far away for context, you can't take too many, and if you don't know how to post them, e-mail them to me, I'll get them on here.

click on my pseudonym in blue for the address.

happy coaching!
buswarrior
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topfrog007
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« Reply #9 on: February 23, 2012, 07:50:26 AM »

This pin under the accelerator.

Can you see it? What activates it? What powers it? Can you disable it, taking precautions for unintended movement, and see if it will back up?

Has anyone else been witness to this pin in their coach?

happy coaching!
buswarrior

I can see the pin, it's maybe the size of a drinking straw and about 4-6" long. It's activated by putting the coach in reverse, other than that I can't get it to move any other way. It sounds like it's air powered. Not sure if I can disable it or not.

@Scott I will try and get some picturers soon.

I am definitely a noobie, there is no denying that!

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Preston - Dothan Alabama - 1986 MCI 102A3
topfrog007
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« Reply #10 on: February 23, 2012, 07:09:14 PM »

Guys,

Here are some pictures of the Pin in the down position, with the Bus off and in Neutral. The second I shift into reverse the pin shoots up and stops the accelerator from being pressed down. Shifting into Neutral, 1st, 2nd, 3rd, 4th and the pin stays down. Only blocks the pedal in reverse.

The pedal and the pin.


Another shot:


Close up of the pin and housing:


What do you think?
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #11 on: February 23, 2012, 07:40:19 PM »

If it were mine, it would be an unnecessary extra... and filed...
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« Reply #12 on: February 23, 2012, 07:43:12 PM »

Short work would be to remove the whole pin and air cylinder assembly.

Though it would be better to troubleshoot the throttle lock system and find out why it's deploying. Not having the operator's and maintenance manuals, I'd grind the pin off, and then destroy something really expensive. BTDT.
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luvrbus
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« Reply #13 on: February 23, 2012, 07:59:43 PM »

That should be a easy fix follow the 1/4 in line to the skinner valve and it is probably controlled by a micro switch on on the gear shift lever and the switch will have a spring looking deal on it.

That is the same cylinder used on the rear of the engine on the 2 strokes for fast idle hold and the shut down ,I would look for a switch to turn it off on the dash somewhere some older school buses had that setup that worked off the stop flag to keep drivers from backing up and hurting children walking behind the bus

good luck   
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Scott Bennett
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« Reply #14 on: February 24, 2012, 05:14:07 AM »

That should be a easy fix follow the 1/4 in line to the skinner valve and it is probably controlled by a micro switch on on the gear shift lever and the switch will have a spring looking deal on it.

That is the same cylinder used on the rear of the engine on the 2 strokes for fast idle hold and the shut down ,I would look for a switch to turn it off on the dash somewhere some older school buses had that setup that worked off the stop flag to keep drivers from backing up and hurting children walking behind the bus

good luck   

I'm with Cliff on this one...definitely some sort of add-on safety mechanism...not something that appears to be related to an actual mechanical issue. I'd disable it for now. But that's me...and I've kicked myself in the past every once in a while for doing that.  Roll Eyes
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Scott & Heather
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« Reply #15 on: February 24, 2012, 10:45:34 AM »

I'm a GM guy, so probably of little use here.  However, do you know the last operator of your coach when it was in passenger service?  If so, can you call and talk with their Superintendent of Maintenance to find out what it is?

I like Clifford's idea about the school service interlock.  These days, drivers are taught not to reverse, this could be some home-brewed device to prevent backing beyond dead idle speed.  I'm doing a lot of cost projections for private sector transit operators.  I just read a Request for Proposals where the public transit system won't allow bus drivers to back up, unless they call Dispatch first for permission.

Arthur
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Arthur Gaudet    Carrollton (Dallas area) Texas 
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« Reply #16 on: February 24, 2012, 11:50:57 AM »

I would expect to see the electrical signal that activates this arrangement to be tied into the circuit that illuminates the back-up tell tale on the dash.

The usual design and execution of a fleet level retrofit is to aim for simplest and cheapest, looking to tie into existing systems, rather than duplicate them.

It may be simply and immediately hobbled by pinching off, or otherwise disconnecting and plugging, the air line supplying it with air pressure. Follow the rest at your leisure?

As for Runcutter's comments, unfortunately, a grown adult, holding a commercial driver's licence, having to call in for permission to reverse...this seems to be inane direction the world is heading.

Let's see, that driver will reverse in a relaxed manner after just admitting to dispatch that they misjudged something?

Self fulfilling prophecy, they will hit more things, not less. Also, it often found that the same properties have poor reversing training to begin with, further promoting a backing accident.

If you can't back up by yourself, should you be allowed to drive forward by yourself?

harumph!

happy coaching!
buswarrior
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« Reply #17 on: February 25, 2012, 08:05:35 AM »

BW, I learned to drive as a fueler/hostler, we used to have to back across the driveway to park -  and overlap mirrors to get an extra bus in. (Today, unfortunately, I wouldn't be able to then squeeze out the door). 

Last year, I was on a city property that has a 100% reflective vest policy.  I walked over from the hotel, got to the security booth, and had to borrow a vest to walk across the parking lot to the office.  (Let's see, I have on a grey suit, blue tie - what color goes best -- the lime green or the bright yellow?)  One of the national management companies has the same policy.  I'd have to put on a vest, to walk 25 feet from my car to the front door.  In my day, we learned to be careful walking around buses -- not the other way around. 

BW raised a good point.  Learn to back up, learn to use your mirrors, learn how to use the pivot point of your bus.  Knowing how to back up, how to maneuver your bus, will make you a better driver in all cases.  There's another factor.  When I developed a presentation on Church Bus safety, I noticed that my church was driving its two vans forward into their chain link enclosure.  That meant, when they wanted to use the vans, they'd back out.  Since there's a day school with young kids, I had the policy changed -- back in, drive out.  Fewer crushed kiddies that way.  It also applies in supermarket parking lots, any environment.  Back in, drive out. 

Sorry to take the thread astray, but I've had to investigate and/or discipline for too damned many accidents.

Arthur
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Arthur Gaudet    Carrollton (Dallas area) Texas 
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Working in the bus industry provides us a great opportunity - to be of service to others
topfrog007
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« Reply #18 on: February 25, 2012, 02:21:14 PM »

Guys,

Tried to get it to go down again, tried all combination switches on dash. Nothing worked. Looked through the manual but couldn't find anything about this little gizmo.

Does anyone know what it might be called? I was hoping to find something in my MCI manual about it.

Thanks.
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #19 on: February 25, 2012, 03:54:49 PM »

Preston, again, I'm a GM guy.  However, in looking at the pictures and reading the responses, I'd wager that it'd be news to MCI.  That was the reason I suggested finding the last passenger-service operator of your coach, if at all possible. 

Here's the question -- can you back up at idle speed, even with the device, or is something else interlocked with it?

Arthur
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Arthur Gaudet    Carrollton (Dallas area) Texas 
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Working in the bus industry provides us a great opportunity - to be of service to others
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« Reply #20 on: February 25, 2012, 04:51:39 PM »

Preston, again, I'm a GM guy.  However, in looking at the pictures and reading the responses, I'd wager that it'd be news to MCI.  That was the reason I suggested finding the last passenger-service operator of your coach, if at all possible. 

Here's the question -- can you back up at idle speed, even with the device, or is something else interlocked with it?

Arthur

Arthur, I left a voicemail on the PO's machine. The bus does move while backing up at Idle, the problem is that I'm parked on a bit of a slope so it only goes so far until the slope becomes too high.

I guess I'm mainly worried about two things:

1. Is it possible the mechanism might be preventing damage to the bus by preventing reverse driving? And if I remove it I risk damaging the bus somehow.
2. I start taking it off and find out I need it later on, or that upon taking it apart that it's much more involved than anticipated.

Thanks,
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #21 on: February 25, 2012, 05:00:00 PM »

I would just disconnect the air line that feeds it and plug it,  or pinch it with ViseGrips. It will be accessible from the spare tire compartment under the floor. It is not hard to plug back in if you decide you need it again.

JC
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JC
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« Reply #22 on: February 25, 2012, 05:52:33 PM »

I did a Google search and learned some school buses have this same feature.  It prevents the driver from reversing (at least greater than idle speed) when the rear emergency door is open.  Do you have an emergency door on your bus?  Is there something else that has a switch on it that feeds a signal to this air solenoid? 

Brian S.
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Brian Shonk
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topfrog007
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« Reply #23 on: February 25, 2012, 06:47:13 PM »

@LostAgain - I think that'll be the way I end up going.

@Depewtee Ahh thats very interesting. Our bus has only one door, the main entrance door. It doesn't make sense that it would let us drive in any forward gear, just not in reverse. I tried every combo on the Dash and nothing seemed to unlock it while in reverse.

After purchasing the coach I believe we went into reverse without any problems at a gas station, for some reason neither of us can remember 100%
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Preston - Dothan Alabama - 1986 MCI 102A3
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« Reply #24 on: February 25, 2012, 08:36:27 PM »

Does that coach have steerable tags?  Try lubing it up it may be a spring loaded air activated switch that is 1/2 froze





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« Reply #25 on: February 27, 2012, 01:06:29 AM »

Why would there be a bypass switch accessible to the driver for some evil device such as this??

Someone smoking something illegal dreamed this accelerator inhibit up, in order to prevent the driver from doing something.

They are not going to then give the driver a switch to defeat it. Kind of a waste of time installing all of that, wouldn't it be?

Crawl into the spare tire compartment and neuter the stupid thing.

It's your bus now, none of us have that thing, or have ever seen one.

And get yourself reversed.

Shoot it before it procreates!

happy coaching!
buswarrior

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thomasinnv
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« Reply #26 on: February 27, 2012, 07:36:25 AM »

I agree with BW and some of the others...yank that stupid thing out and get on with your life. You drive the bus, don't let it drive you!
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
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