C3.4B Engines for Caterpillar Built Machines Caterpillar

The cylinder compression test should only be used in order to compare the cylinders of an engine. If one or more cylinders vary by more than 350 kPa (51 psi), the cylinder and related components may need to be repaired.

A compression test should not be the only method which is used to determine the condition of an engine. Other tests should also be conducted in order to determine if the adjustment or the replacement of components is required.

Before the performance of the compression test, make sure that the following conditions exist:

• The battery is in good condition.

• The battery is fully charged.

• The starting motor operates correctly.

• The valve lash is correct.

• All glow plugs are removed.

• The ECM is powered.

• The fuel pressure sensor is connected.

• The suction control valve is connected.

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Illustration 1	g03698266
Typical example

1. Remove the glow plug (1). Refer to Disassembly and Assembly, "Glow Plugs - Remove and Install" for the correct procedure.

2. Install a suitable gauge for measuring the cylinder compression in the hole for the glow plug (2).

3. Remove the fuse for the glow plugs.

4. Operate the starting motor in order to turn the engine. Record the maximum pressure which is indicated on the compression gauge.

5. Repeat steps 2 and 4 for all cylinders.

6. Install the fuse for the glow plugs.