Stanadyne DB2 and DB4 Pump Removal and Installation


All Stanadyne DB4 and most DB2 injection pumps will have a retained drive shaft ( the shaft stays in the pump when the pump is removed from engine). Clean the exterior of the injection pump and mounting surfaces.
IMPORTANT: Never steam clean or pour cold water on an injection pump while the pump is running or while it is warm. Doing so may cause seizure of the injection pump.
1. Disconnect shut-off cable and speed control linkage, if equipped.
2. Disconnect electrical connection to shut-off solenoid or throttle positioning solenoid, if equipped.
3. Disconnect cold start switch, if equipped. Tag electrical wires for correct reassembly.
4. Disconnect all high-pressure injection lines.
5. Disconnect fuel return line and fuel supply line.
6. Remove injection pump drive gear cover.
7. Remove injection pump drive gear cover. Remove drive gear retaining nut and washer from end of pump shaft. Be careful not to let the washer fall inside timing gear cover.
NOTE: The injection pump drive gear fits snugly onto a tapered drive shaft and is indexed by a hollow pin or Woodruff key installed in drive shaft.
8. Use a gear puller to remove the drive gear from the tapered shaft. Be careful to not damage the end of the injection pump drive shaft. Check to make sure marks are present and lined up on both the pump mounting flange (B) and on the front cover (A). If the timing mark is not clearly visible, scribe a line on the front cover that matches the timing line on the injection pump.
9. Remove the injection pump mounting nuts and remove the injection pump from the mounting


1. Install seal into groove on front face of pump mounting flange. Slide injection pump onto mounting studs while inserting pump shaft into drive gear. IMPORTANT: Most drive shafts have a “Dot to Dot” type set up on the drive.
2. Check pump shaft and index pin for proper alignment with pump drive gear key slot. IMPORTANT: Shaft roll pin may be easily damaged if improperly assembled. Pump drive gear should not move when initially installing pump index pin into drive gear key slot.
3. Pump should sit squarely and solidly on mounting pad when slight pressure is applied.
IMPORTANT: DO NOT use tightening force of pump mounting stud nuts to pull pump shaft into drive gear.
4. With the pump shaft index pin properly engaged in the drive gear key slot, finger-tighten mounting stud nuts.
5. Push pump drive gear firmly onto shaft taper. Install washer and retaining nut (C) onto end of shaft. Tighten retaining nut to the specified torque, per your engine service manual. Install access cover plate using a new O-ring, if needed.
6. Align timing mark on pump flange with timing mark on front plate.
7. Tighten the mounting nuts/bolts securely.
8. Then install the injection lines, but leave the injector ends loose.
9. Reconnect the fuel inlet and return line, leaving the inlet line loose for bleeding procedures.
10. Reconnect the shutoff solenoid (if equipped).
11. Reconnect the throttle linkage.

Priming and Starting

1. Open the bleeder screw on the secondary filter (if equipped) and operate the hand primer to bleed the air from the system.
2. When fuel flows freely from the fuel inlet line, tighten the fuel inlet line at the injection pump.
3. Leave the shut-off disconnected or in the off position and crank the engine over for 10 seconds.
4. Connect the electrical shut off solenoid.
5. Crank the engine to start.
6. If the engine will not start, loosen the injection lines at the injectors, one line at a time. Crank the engine over until fuel free of bubbles flows from the injector, tighten the injection line.
If you have any questions about the information covered in this guide, please contact
Diesel Care & Performance
at 901-343-6453 or