Air throttle

[BillC]

   Is there a diagram or any info hooking up a Williams air pedal, like where to put the air lines.   My cable broke and I have had this Williams air pedal for 3 or 4 years with the 3/8 air line already in the tunnel, but have lost the info with it.  So i need the modulator # for the trans and where to bye it and any thing else i need for the install.  Its going in a 83 Eagle model 10s with a 6v92 and 740 trans.   Bill C 

[JackConrad]

Bill,
   I purchased my modulator from Luke at US Coach. I ran a 3/8 line from the accessory tank under the driver's seat to an adjustable pressure regulator and a 3/8 line from the regulator to the IN port on the foot valve. I also ran a 3/8 line from the foot valve exhaust port through the floor. The third port on the foot valve connects to the 3/8 line going to the engine compartment. In the engine compartment install a T in the 3/8 line from the front of the bus. From this T, use 2 3/8 lines that are exactly the same length. Attach one of these to the air control unit on the governor and the other line to the air modulator on the transmission.  Jack

[BillC]

Thank you Jack I will call Luke Monday,  do I  just remove the cable and linkage and the govener will take its place.       Is there a big difference between the cable and air throttle?   Thanks again    Bill C

[chris4905]

Bill,

Take a look at:
http://www.wmco.com/products/throttle_controls_catalog.pdf

Special attention probably to page #16.

I have only had an air throttle.  I understand a cable throttle is "immediate" response.  You probably know better than I.  With an air throttle there is a short (maybe 1-2 second delay from pressure on the throttle until response at the engine.

Hope this helps.

Chris

[JackConrad]

Thank you Jack I will call Luke Monday,  do I  just remove the cable and linkage and the govener will take its place.       Is there a big difference between the cable and air throttle?   Thanks again    Bill C

   Air throttle is different than cable. Much less back pressure on throttle pedal. My problem is that with so little back pressure, I find myself driving faster than I want to. There is a slight lag between throttle application and engine response to throttle.  I got used to it pretty quick.
     I removed the cable and the modulator, installed the air modulator (I used the same clamp to hold the new modulator in place), and connected the air line to the air modulator. NOTE: have a drain pan under the transmission when you pulled the old modulator out (don't ask how I know this LOL).  Make sure the little pin does not come out when you remove the cable modulator. Lube the O ring on the new modulator before installing it, being careful not to nick or cut the O ring.  The throttle actuator sits on top of the governor and connects to the throttle shaft that sticks up through the gevernor top plate. Jack
    Here a few phots of the air modulator and 2 differnet styles of air throttle actuator linkage on an 8V71 governor.

     

[chris4905]

Here's a photo of the actuator on my 6V92.

[mccarlk]

in the pic with the red engine there is a air controled valve to the left, in the pic you can only see part of it , what is it, and were should it get its air from, thanks

[JackConrad]

in the pic with the red engine there is a air controled valve to the left, in the pic you can only see part of it , what is it, and were should it get its air from, thanks

That is the fast Idle and receives air pressure from the fast idle solenoid that in located next to the engine stop solenoid. The fast idle solenoid also provides air pressure to the piston shown in the upper right corner of the photo directly above the red engine photo (same post by me). This piston is to prevent manual throttle application when fast idle is engaged.  Jack

[mccarlk]

thanks jack, i have been looing in all my books with no answer, i thought the one on top was the only fast idle, im so close to starting this beast it hurts,

[JackConrad]

thanks jack, i have been looing in all my books with no answer, i thought the one on top was the only fast idle, im so close to starting this beast it hurts,

The fast idle assembly on the left of the red engine governor is removed to install a Jake Brake buffer switch (which is why most people lose fast idle when Jakes are installed). Jake sells a buffer switch that includes fast idle but it is rahtrer $$$.  Jack

[Airbag]

FWIW make sure you have locking features on the hardware for those throttles. I had a bus with a run away Williams air throttle on a front engine bus while exiting the freeway with a load of kids. The linkage failed because a bolt backed out and did not allow the engine to throttle down from 1800 rpms. It got my attention. I probably did not handle the situation properly but the brakes did the job without having to put the transmission in neutral and letting the engine over rev. They did not teach a proper procedure for this in class. The mechanic later told me it usually ends in disaster. Your probably thinking the throttle should be spring loaded to idle but there are several bolts involved and if this particular one comes out it won't allow it to idle. I know the Cummings set up is different than DD but just be safe, star washers, split washers, and cotterpins or safety wire are cheap.