Detroit Diesel — Compression Testing
Testing & diagnosis · Cylinder / cylinder head
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- Coolant temperature must be between 70-95°C (158-203°F).
Procedure
- Set the parking brake and chock the tires; run the engine until it reaches operating temperature, then shut down.
- Remove the fuel injector nozzle.
- Insert the compression test adaptor J-46386 (or J-45392 tensioning adapter) into the cylinder head.
- Attach the compression tester J-6692-B to the test adaptor.
- Remove the electrical connectors from the MCM/unit pumps so the engine will not start.
- Crank the engine at least 8 engine revolutions per cylinder and compare gauge to specifications.
- Reinstall nozzle holder and tighten retaining bolt to 50 N·m (37 lb·ft); repeat for each cylinder.
Tools required
- Compression test adaptor J-46386 Amazon
- Compression gage J-6692-B Amazon
- Tensioning adapter J-45392 Amazon
- DDDL 7.0 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Minimum compression 2800 kPa (406 psi)
- Permissible difference 400 kPa (58 psi)
- Retaining bolt 50 N·m (37 lb·ft)
Source: Detroit Diesel 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.