Bus Conversions dot Com Bulletin Board
September 01, 2014, 02:46:40 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an E-Mag Subscription: You can zoom in to make the text larger and easier to read.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1]   Go Down
  Print  
Author Topic: Bus wont go off fast idle!  (Read 1008 times)
trey
Newbie
*
Offline Offline

Posts: 8




Ignore
« on: July 24, 2007, 05:22:57 PM »

I have an MCI 9 with detroit 8v92tt and it wont go off fast idle. on the engine there is this pill bottle size thing that pushes out a little pin that keeps the throttle from moving/stuck on fast idle. I have to push the brakes a lot letting all the air out before this little pin will go back in. what is this and whats wrong with my bus that causes it to get stuck on fast idle? Im new to the bus/diesel engine world can anybody help me out?
thanks
trey
Logged
Barn Owl
Roanoke, VA
Hero Member
*****
Offline Offline

Posts: 2046


PD4106-1063 "Wheezy Bus"




Ignore
« Reply #1 on: July 24, 2007, 05:33:31 PM »

Your electric/air solenoid valve up stream is stuck in the open position. At the moment, my mind is blank on the name of that thing. Someone help! Starts with an S.
« Last Edit: July 24, 2007, 07:56:31 PM by Barn Owl » Logged

L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
Its the education gained, and the ability to apply, and share, what we learn.
Have fun, be great, that way you have Great Fun!
Barn Owl
Roanoke, VA
Hero Member
*****
Offline Offline

Posts: 2046


PD4106-1063 "Wheezy Bus"




Ignore
« Reply #2 on: July 24, 2007, 05:39:43 PM »

I remember! It's a skinner valve.
Logged

L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
Its the education gained, and the ability to apply, and share, what we learn.
Have fun, be great, that way you have Great Fun!
Dreamscape
Guest

« Reply #3 on: July 24, 2007, 07:18:39 PM »

Barn Owl is right, that pill bottle thingy is a small pneumatic cylinder that works off the skinner valve. It is probably all gummed up and wont' let the air dump when you take power off the skinner valve. HTH.

Happy Trails,

Paul

Dreamscape
Logged
FloridaCliff
Hero Member
*****
Offline Offline

Posts: 2458


"The Mighty GMC"




Ignore
« Reply #4 on: July 24, 2007, 07:22:31 PM »

Remember, its broke.

Not much to take apart and clean up.

This is all heavy duty and rebuildable equipment and most are very simple to rebuild.

Give it a try!

Cliff
« Last Edit: July 24, 2007, 07:26:14 PM by FloridaCliff » Logged

1975 GMC  P8M4905A-1160    North Central Florida

"There are basically two types of people. People who accomplish things, and people who claim to have accomplished things. The first group is less crowded."
Mark Twain
RJ
Former Giant Greenbrier Owner
Hero Member
*****
Offline Offline

Posts: 2799





Ignore
« Reply #5 on: July 24, 2007, 10:01:51 PM »

Trey -

To elaborate a little more:

The unit on the engine that pushes on the throttle lever can be removed, disassembled, cleaned and reassembled easily.  Lube it with something other than WD-40, use 3-in-1 or similar.

Next, follow the air line that attaches to the piston assembly you just cleaned back to the engine bulkhead.  Here you'll find the skinner valve, and chances are it's stuck.  A little more complex to clean, sometimes it's better to replace, they're not that expensive.  (Of course, you can try the "cheap" method first - with the engine running on fast idle, switch off the F/I.  If it doesn't drop, then rap on the skinner valve with a rubber dead blow mallet to see if that unsticks the valve.  Regardless of the results, order a new one!)

FWIW & HTH. . .

 Wink
Logged

RJ Long
PD4106-2784 No More
Fresno CA
Dreamscape
Guest

« Reply #6 on: July 25, 2007, 02:05:29 AM »

Can someone post some phone numbers for Trey? I suggest replaceing the parts as that is the best way to go. I am traveling and don't have these available.

Paul
Logged
Don4107
Sr. Member
****
Offline Offline

Posts: 407





Ignore
« Reply #7 on: July 25, 2007, 11:16:25 AM »

Trey,

Are you sure that the fast idle switch is not turned on?  Could have been bumped.

Sounds like the cylinder is working since when you pump down the air it retracts and allows the engine to idle.  Indicates the problem is the skinner valve.  It is stuck or power is being applied to activate it.  Trace the air line back from the cylinder to the skinner valve. 

Check to see if power is being applied to the valve.  It should only have power when the fast idle is turned on.  If there is no power, try tapping on it.  If that causes it to close, plan on changing it anyway.  It will stick again.

Good luck

Don 4107
Logged

Don 4107 Eastern Washington
1975 MCI 5B
1966 GM PD 4107 for sale
1968 GMC Carpenter
Stan
Hero Member
*****
Offline Offline

Posts: 973




Ignore
« Reply #8 on: July 25, 2007, 12:06:15 PM »

I don't know what the costs are now on Skinner valves, but when I was working with them a lot, a rebuild kit was about 10% of the cost of a new valve. With the valve in a vise, it is about a ten minute job to replace the plunger and gaskets. I guess the decision to repair or replace is determined by how much you value your labor.
Logged
FloridaCliff
Hero Member
*****
Offline Offline

Posts: 2458


"The Mighty GMC"




Ignore
« Reply #9 on: July 25, 2007, 01:22:54 PM »

Stan,

I bought one new and rebuilt my used one.

You are 100% right on the price difference.

Found this out a little to late the first time.

I now have a good spare, and will rebuild any future ones.

Cliff
Logged

1975 GMC  P8M4905A-1160    North Central Florida

"There are basically two types of people. People who accomplish things, and people who claim to have accomplished things. The first group is less crowded."
Mark Twain
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!