1989 beaver Marquis 6v92 Detroit idle adjustment

[Sigbert All III]

Need to adjust idle up some on my Detroit so alt will charge 12 volts only showing 11 volts unless give a little throttle and was wondering where idle adjuster is on engine

[Eric Maclean]

Sigbert
The idle on your Detroit diesel is controlled by the mechanical governor, that governor controls the fuel racks on the injectors via series of linkages.
There are three adjustments available in the governor
1) idle speed ( or low speed ) screw.      used to set the low speed idle
2) idle buffer screw.                        Used to dampen the idle movement to help control idle roll or surge (not used to set idle speed)
3) high speed or maximum RPM         used to set engine Maximum governed RPM

If you decide to make any adjustments be VERY CAREFUL as a mistake in this venture can end in a runaway and or severe engine damage there fore it is important to understand the governor operation before attempting any adjustments.

The governor on a 6V-92 is located at the front top of the engine with the throttle linkage connected to the top of it
The adjustments are located under a cylindrical shaped cover on the side of the governor housing, this cover is held on by two small machine screws and once removed the adjustments are acceptable.
If your coach has an air throttle it is connected as part of that cover and complicates the process some what.
I have included videos showing both a standard mechanical throttle and an air throttle for reference.

The idle adjustment is made will the engine warm at operating temperature running at idle by unlocking the small lock nut on the Allen headed screw and turning the screw clockwise (in) to increase idle speed and counter clockwise ( out ) to decrease idle speed make any adjustments with very small movements 1/16 of a turn or less and give the engine several seconds to react and settle before making another adjustment. Remember to tighten the lock nut after your done .
DO NOT make any adjustments to the outer.barrel with the larger hex end as this is the high speed adjustment and will change the engines maximum RPM

Here are a couple of video links which may help you understand the whole governor operation.
Although the engines in these videos are not 6V-92s the adjustments are similar.

https://youtu.be/z-jjTaZlu28

https://youtu.be/rvB1Qc5yaj4

https://youtu.be/zLL6YCVRCGY

Hope this helps
Eric