John Deere — Check and Adjust Slow Idle Speed—Denso Fuel Injection Pump
Adjustments · Denso injection pump governor
From a John Deere service manual covering: 4045, 4045TF120, 6068, 6068TF120, 6068TF250, T06068TF220, T06068TF250, T06068TFM50. Check it applies to your exact model before use.
Applies to: John Deere 4045, John Deere 4045TF120, John Deere 6068, John Deere 6068TF120, John Deere 6068TF250, John Deere POWERTECH 4.5 L & 6.8 L Diesel Engines (4045 / 6068) engine
Before you start
- ALWAYS STOP ENGINE before making adjustments.
- Bumper spring screw should not be used by itself to change engine speed more than 50 rpm.
Procedure
- With engine running, pull governor control lever rearward to slow idle speed position; check speed.
- Remove slow idle stop screw cover.
- Loosen lock nut and back out bumper spring adjusting screw three turns.
- Loosen lock nut and adjust slow idle stop screw to obtain idle 30—50 rpm less than desired slow idle setting.
- Turn bumper spring adjusting screw in to increase engine speed a maximum of 30—50 rpm to desired slow idle.
- If surging persists, replace bumper spring and adjustment screw.
- Recheck fast and slow idle speeds; readjust slow idle if needed.
- Check all adjusting screw lock nuts for tightness; install covers.
- Connect fuel shut-off cable and speed control rod.
Tools required
- Tachometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: John Deere 4045 →, John Deere 6068 →, John Deere 6068TF250 →
Source: John Deere 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.