Cummins/Onan — Injectors Replacement
Repair & overhaul
From a Cummins/Onan owner's manual covering: 4B3.9, 4BT 3.9, 4BTA 3.9, 6B5.9, 6BT 5.9, 6BTA5.9, B5.9-160, B5.9-175, B5.9-190, B5.9-210, B5.9-230. Check it applies to your exact model before use.
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Before you start
- Injector must not rotate in bore of cylinder head; damage to cylinder head will result.
Procedure
- Thoroughly clean around injectors.
- Disconnect high pressure fuel lines. Disconnect fuel drain manifold.
- Remove injectors. Hold injector body with 16 mm wrench while loosening hold-down nut with 24 mm box end wrench.
- Clean injector nozzle bore using Service Tool No. 3822509.
- Remove injector hold-down nut and apply anti-seize compound to injector surface. Avoid getting in fuel drain hole.
- Install new o-ring in hold-down nut. Apply anti-seize to threads.
- Assemble injector and new copper washer. Use only one copper washer.
- Install injectors; protrusion on nozzle fits notch in head.
- Tighten injector nozzle nuts. Torque 60 N·m [44 ft-lb].
- Install fuel drain manifold. Torque 9 N·m [7 ft-lb].
- Install high pressure fuel lines. Torque 30 N·m [22 ft-lb].
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Injector nozzle nut 60 N·m [44 ft-lb]
- Fuel drain manifold 9 N·m [7 ft-lb]
- High pressure fuel lines 30 N·m [22 ft-lb]
Source: Cummins/Onan owner's 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.