Removal and install of Stanadyne DB2 and DB4 Pumps

Removal and install of Stanadyne DB2 and DB4 Pumps


To remove the Stanadyne DB2 or DB4 injection pump:

  1. Clean the exterior of the injection pump and mounting surfaces.
  2. Disconnect the shut-off cable, speed control linkage, and electrical connections.
  3. Disconnect all high-pressure injection lines using a backup wrench.
  4. Disconnect the fuel return line and fuel supply line.
  5. Remove the injection pump drive gear cover.
  6. Using a gear puller, remove the drive gear from the tapered shaft.

 Inspect DB2 -DB4 Pump

To inspect the injection pump:

  1. Check for timing marks on the pump mounting flange and the front cover.
  2. Remove the injection pump mounting nuts and take out the pump from the mounting studs.
  3. Inspect the injection pump mounting hole and surface for cleanliness and smoothness.
  4. Check the injection pump drive shaft for metal transfer and damage to the index pin.



To install the injection pump:

1. Install the seal into the groove on the front face of the pump mounting flange.
2. Align the pump shaft and index pin with the pump drive gear key slot.
3. Ensure the pump sits squarely and solidly on the mounting pad.
4. Finger-tighten the mounting stud nuts with the index pin engaged in the drive gear key slot.
5. Push the pump drive gear firmly onto the shaft taper and tighten the retaining nut to the specified torque.


 Housing Timed Injection Pumps


  1. Align the timing mark on the pump flange with the timing mark on the front plate.
    7. Tighten the mounting nuts/bolts securely.
    8. Install the injection lines, leaving the injector ends loose.
    9. Reconnect the fuel inlet and return lines, leaving the inlet line loose for bleeding procedures.
    10. Reconnect the shut-off solenoid and throttle linkage.

Install DB2 DB4 Injection pump

To prime and start the engine:

  1. Open the bleeder screw on the secondary filter and operate the hand primer to bleed the air from the system.

 To prime and start the engine

  1. Tighten the fuel inlet line at the injection pump when fuel flows freely.
  2. Leave the shut-off disconnected or in the off position and crank the engine for 10 seconds.
  3. Connect the electrical shut-off solenoid.
  4. Crank the engine to start.
  5. If the engine does not start, loosen the injection lines at the injectors one at a time, crank the engine until fuel free of bubbles flows from the injector, and tighten the injection line.

Note: Use two wrenches if needed and avoid cranking the engine with all injection lines loose to prevent airlocks.


Use two open ended wrenches if if needed.

DB2 DB4 Install

You can experience an airlock while trying to bleed the fuel system if all the injection lines are loose at one time while cranking the engine.



Back to blog

Leave a comment

Please note, comments need to be approved before they are published.