Re: Governors on 345/392 engines...

[eldon_mcf@domain.elided (Eldon L McFarling)]

     < jmbrodsky@domain.elided>  wrote:

  <<  The questions is:  How does the governor work to limit the revs at 
     3900 for the 345 and 3600 for the 392?  Is it electrical, and if 
     so, can I use it to power a tach drive?  If it's mechanical 
     how-d-hell do they do it?  It seems to really drop off quick in 
     power when I get around 3500rpm, but it doesn't sound like it's 
     cutting the ignition.>>

  Joel,  

      There are two types of governors used on IH gas engines,  both
operate similarly. The main difference is how the control part of the
system operates, either a centrifugal valve is used in the distributor,
or an electric solenoid valve, and electronic control unit are used to
control vacuum applied to the governor diaphragm.  The (primary) throttle
plates  are opened by a spring, and closed by the mechanical linkage
connected to the accelerator, or by a vacuum diaphragm (governor
diaphragm) on the carburetor. The vacuum diaphragm can override the
mechanical linkage, so the speed can be controlled regardless of the
accelerator position.  

     Vacuum is supplied thru a passage in the carburetor body to the
governor diaphragm, and to the centrifugal valve, or solenoid valve.
Below governed speed the valves remain open, and no governor action is
produced. when governed speed is reached, the centrifugal, or solenoid
valve is closed, and vacuum is applied to  the governor diaphragm closing
the throttle plates, and thus limiting the engine speed.

      For the electronic system an electronic control unit that looks
similar to a "gold box" ignition module, is connected to the negative
side of the coil to sense the engine rpm. This is connected to  the same
terminal on the coil that  you would use to connect an electric
tachometer.  The tachometer  should be connected to the coil terminal,
not the ECU wiring.

    If you have the distributor controlled governor there will be 1, or 2
vacuum lines between the carb, and distributor (besides the vacuum
advance). The valve in the distributor can be adjusted to change the
governed speed.

      If you have the electronic governor the ECU module is mounted to
the firewall,  and the solenoid is attached to the carb. The ECU has a
preset speed, and cannot be adjusted.

good luck


Eldon McFarling
Ceresco, NE
'80 Scout II Turbo Diesel
Eldon_McF@domain.elided
IH SCOUT DIESEL PAGE    http://members.aol.com/EldonMcf/scoutd.html