Engine Compression Test

Engine Mechanical - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5527861 Single Use Fasteners and Components Glow Plug [6x] Special Tools EN-26999 Compression Gauge EN-46722 Compression Gauge Adapter Equivalent regional tools: Special Tools Technical Requirements Ensure that the vehicle battery is in good condition, and fully charged or the battery is connected to a battery charger. The battery voltage should be >12,5 V. Operate the vehicle until the engine is at normal operating temperature. The engine oil temperature should be >80°C (>176°F). Preliminary Procedures

Engine Compression Test — figure 1

1. Intake Manifold Cover Bolt (1) » Remove
2. Intake Manifold Cover (2) » Remove

Engine Compression Test — figure 2

3. Clamp (1) » Loosen [2x]
4. Charge Air Cooler Outlet Air Hose (2) » Remove

Engine Compression Test — figure 3

Note

Do NOT disconnect the throttle body electrical connector.

5. Throttle Body Bolt (3) » Remove [3x]
6. Throttle Body (1) » Position aside
7. Throttle Body Gasket (2) » Remove and DISCARD

Engine Compression Test — figure 4

8. Electrical Connector (1) @ Glow Plug » Disconnect [6x]

Engine Compression Test — figure 5

Caution

Ensure each glow plug is fully intact when removed from the cylinder head. A broken tip could remain within the combustion chamber, which may not be obvious during removal. Damage to the engine may result if a broken glow plug tip remains within the engine.

Note

Glow plugs must be discarded whenever removed, and replaced with NEW. Handle with extreme care, do not allow glow plugs to touch each other. Do not use power tools to install glow plugs. Use a suitable, commercially available glow plug socket. Cylinder head removal may be required to retrieve a broken tip.

9. Glow Plug (1) » Remove [6x]
10. Inspect each glow plug tip and ensure the glow plug is not broken. If a broken tip is suspected, inspect the combustion chamber for the glow plug tip.
11. Fuel Pump Relay » Remove For component location, refer to Engine Controls Schematics. For removal procedure, refer to Electrical Relay Replacement.

Warning

Refer to Eye Protection Warning.

12. Crank the engine with the starter motor for 5 seconds to remove any foreign substances from the cylinders.

Engine Compression Test — figure 6

13. Install the EN-26999 Compression Gauge and EN-46722 Compression Gauge Adapter in the glow plug hole for the cylinder being checked. Measurement Procedure

Warning

Refer to Eye Protection Warning.

Caution

Do not add oil to any cylinder during a compression test as extensive engine damage may result.

Note

A second technician is required.

1. Check the compression of cylinder 1: 1.1. Turn the ignition ON, with the engine OFF. 1.2. Using the vehicle starter motor to crank the engine. 1.3. Observe the gauge and note the reading as the compression test is being performed.

2. Repeat the procedure for all remaining cylinders.

3. Compare the compression value of all cylinders.

4. The minimum compression in any cylinder is 1800 kPa (261 psi). There should not be more than 10 percent difference between a suspect cylinder and the average compression of all 6  cylinders.

5. If one or more cylinders fails to meet the specified compression range, refer to Cylinder Leakage Test to find the leakage. Subsequent Procedures

6. Fuel Pump Relay » Install For component location, refer to Engine Controls Schematics. For installation procedure, refer to Electrical Relay Replacement.

7. Remove the EN-26999 Compression Gauge and EN-46722 Compression Gauge Adapter from the glow plug hole.

Caution

Refer to Fastener Caution.

Note

The ceramic glow plug technology is sensitive to collision, drops, or general impact Avoid side force or the bending of the tip during the installation in the head. Replace the glow plug if one or more of these conditions is suspected. Glow plugs must be discarded whenever removed, and replaced with NEW. Handle with extreme care, do not allow glow plugs to touch each other. Do not use power tools to install glow plugs. Use a suitable, commercially available glow plug socket. First install glow plugs by hand at least 3 turns into the cylinder head. Avoid canting of the glow plugs during the insertion process into the cylinder head.

3. Glow Plug (1) » Install and tighten [6x] — Fastener Specifications

4. Electrical Connector (1) @ Glow Plug » Connect [6x]

5. Throttle Body Gasket (2) » Install NEW

6. Throttle Body (1) » Install

7. Throttle Body Bolt (6) » Install and tighten [3x] — Fastener Specifications

8. Charge Air Cooler Outlet Air Hose (2) » Install

9. Clamp (1) » Install and tighten [2x] — Fastener Specifications

10. Intake Manifold Cover (2) » Install

11. Intake Manifold Cover Bolt (1) » Install and tighten — Fastener Specifications