Cummins/Onan — Timing the PLB Pump - Depth Micrometer Method
Adjustments · PLB injection pump
From a Cummins/Onan service manual covering: 2.5A, 2.5L, 2.7 AJ, 4.0CCK, 6.0CCKB, 6.5 NH, JC - 3CR / 96 T. Check it applies to your exact model before use.
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Before you start
- Injection pump must be timed on the compression stroke, not the exhaust stroke.
Procedure
- Install pump tappet in its recess and position flywheel port closing mark at timing pointer on compression stroke.
- Measure distance from pump mounting pad to tappet center with a depth micrometer.
- Subtract the depth from the 4.670-inch (42.4 mm) port closing dimension to get shim thickness.
- Select correct shims and install pump.
Tools required
- Depth micrometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Port closing dimension 4.670 inch (42.4 mm)
- Shim thickness 0.006 to 0.052 inch (0.15 to 1.32 mm)
Source: Cummins/Onan 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.