Cummins/Onan — Governor Service
Testing & diagnosis · Electronic governor control, actuator and speed pickup
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDGDA, Cummins/Onan MDGDB
Procedure
- Push the fuel injection pump lever to full power by hand; there should be no binding in the linkage.
- If the actuator does not drive to full power, disconnect the two actuator leads and connect battery voltage across them; replace the actuator or control unit as indicated.
- If speed is still unstable, reinstall the magnetic speed pickup: bar the engine until a gear tooth aligns, thread the unit in by hand, back out one quarter turn and set the locknut.
- Measure speed pickup output voltage while cranking with leads reconnected via bare wire links and fuel solenoid disconnected.
- Replace the speed pickup if the meter indicates less than 2.5 volts; replace the control unit if voltage is at least 2.5 volts.
- Follow each lead out of the governor control unit to its connector; tighten or repair any loose, dirty or corroded connector and try to start.
Tools required
- AC voltmeter (at least 5000 ohms/volt impedance) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Replace the speed pickup unit if output is less than 2.5 volts
- Replace the control unit if voltage is at least 2.5 volts
Full service-parts list: Cummins/Onan MDGDA →, Cummins/Onan MDGDB →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.