Cummins/Onan JWC4-10S-3 — Setting Ignition Timing
Adjustments · ignition unit / distributor
For the Cummins/Onan JWC4-10S-3, from the Cummins/Onan service manual.
Browse Cummins/Onan generators & specs →
Procedure
- Remove cover from timing hole on flywheel housing.
- Crank engine slowly until No. 1 piston is coming up on compression and IGN mark is centered in timing hole.
- Place distributor rotor arm in line with No. 1 tower so breaker contacts are just opening.
- Set unit in place, engage driving lug, push down and install hold-down screw.
- Rotate case until contacts are just breaking and lock clamp screw.
- Start engine and recheck timing with neon timing light; retard spark if pinging knock occurs.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Breaker contacts open .020 in
- IGN mark centered in timing hole
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.