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Author Topic: Tag Axle Low Air indicator light on. Can't reverse  (Read 2698 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
buswarrior
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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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Frozen North, Greater Toronto Area
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
thomasinnv
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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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buswarrior
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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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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
buswarrior
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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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Frozen North, Greater Toronto Area
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
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
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buswarrior
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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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Brassman
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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
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
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