Detroit Diesel — Adjust Idle Speed (Limiting Speed Mechanical Governor)
Adjustments
From a Detroit Diesel service manual — check it applies to your exact model before use.
Procedure
- With engine running at normal operating temperature and buffer screw backed out, turn idle speed adjusting screw until engine operates approximately 15 rpm below recommended idle speed.
- Hold idle screw and tighten lock nut.
- Install high-speed spring retainer cover and tighten the two bolts.
Tools required
- Tachometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Recommended idle speed 400-450 FridayParts $5324.98 rpm (may vary with application)
Source: Detroit Diesel 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.