Cummins/Onan — Starter Motor Checkout
Testing & diagnosis
From a Cummins/Onan service manual covering: JC 15.0, JC15, MDJC 10.0, MDJE 75, MJC15. Check it applies to your exact model before use.
Applies to: Cummins/Onan MDJC, Cummins/Onan MDJE, Cummins/Onan MDJF
Procedure
- With the starting motor operating, check voltage drops from battery ground terminal post to cylinder block, cylinder block to starting motor frame, and battery positive post to battery terminal stud o
- Normally each should be less than two volts.
- Thoroughly clean all connections in any part of the circuit showing excessively high voltage drops.
Tools required
- voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- less than two volts
Full service-parts list: Cummins/Onan MDJC →, Cummins/Onan MDJE →, Cummins/Onan MDJF →
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.