Cruze

Engine Compression Test

Special Tools

EN-48248 Cylinder Compression Pressure Gauge

For equivalent regional tools, refer to Special Tools .

1. Ensure that the vehicle's batteries are in good condition, and fully charged.
2. Operate the vehicle until the engine is at normal operating temperature.
3. Shut off engine.
4. Disconnect the crankshaft position sensor.
5. Remove the fuel pump relay from the underhood fuse block.
6. Remove all 4 fuel injectors. All 4 fuel injectors must be removed from the engine during each cylinder test to obtain valid test results.

Note: The engine cranking time for the compression test should be less then 10 seconds and at 30 second intervals.

7. Crank the engine with the starter motor for 5 seconds to remove any foreign substances from the cylinders.
8. Prior to taking a compression reading, verify the cranking speed is greater than 140 RPM. If the cranking speed is below 140 RPM, repair the slow cranking speed condition before continuing with the compression test. Refer to Engine Cranks Slowly .
9. Install EN-48248 gauge in the fuel injector hole for the cylinder that is being checked.
10. Using the vehicle's starter motor, rotate or crank the engine for 4 compression strokes, puffs, for the cylinder being tested.
11. Observe the compression gauge and note the reading as the compression test is being performed. A normal cylinder reading will be indicated if compression builds up quickly and evenly to the specified level. An abnormal reading will be indicated if compression is low on the first compression stroke, starts increasing on the following compression strokes but does not reach the specified level.
12. Record the compression reading for the cylinder just tested.
13. Disconnect the compression gauge from the fuel injector hole.
14. Repeat steps 9-13 for all remaining cylinders. All 4 cylinders must be tested to obtain valid test results. Record the readings.
15. The normal compression in any one cylinder is 2600 kPa (377 psi). There should not be more than 260 kPa (37 psi) difference between a suspect cylinder and the average compression of all 4 cylinders.

•	Normal - Compression builds up quickly and evenly to the specified compression for each cylinder.

•	Piston rings leaking - Compression is low on the first stroke. Compression builds up with the following strokes but does not reach normal.

•	Valves leaking - Compression is low on the first stroke. Compression usually does not build up on the following strokes.