N14 Base Engine Troubleshooting and Repair Manual – 006-046   STC Oil Delivery System Blockage

Check the STC plumbing.

NOTE: Make sure the STC oil supply line is plumbed between the STC valve oil outlet fitting and the STC rocker housing connection.

Check for a collapsed or restricted oil supply line from the STC valve to the STC rocker housing connection.

Check the STC valve calibration. Refer to Procedure

006-037-001.

Remove the shutoff valve from the STC rocker housing connecting.

Install a shop air line regulator, Part No. ST-990-40, and a 0-1109 kPa [0-160 psi] pressure gauge, Part No. 3375275, to the STC rocker housing connection.

Remove the rocker lever cover assembly. Refer to Procedure

003-011-002.

Apply 278 kPa [40 psi] air pressure to the STC oil manifold to push oil out of the lines.

Lower the pressure to 69 kPa [10 psi].

Air will leak around each injector link.

If the air leakage around a link is excessive, check the injector overhead adjustment. Refer to Procedure

003-004-010.

If air does

not
leak around each injector tappet link, remove the injector. Refer to Procedure

006-026-002.

Once the injector is removed, air

must
leak at the STC oil supply tube.

If air does

not
leak at the oil supply tube, check the oil transfer tube and oil supply tube for restriction at the problem cylinder.

Listen for large air leaks at joints between the STC oil manifold and transfer tubes, or transfer tubes and injectors. This will indicate a missing or cut o-ring, or leaking oil plumbing.

Replace the defective part(s).

Remove the pressure gauge, tee fitting, and shutoff valve from the STC rocker housing connection.

Connect the oil supply line to the STC rocker housing connection.