Compression Inspection
WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
- Hot engines and oil can cause severe burns. Be careful not to burn yourself during removal/installation of each component.
- Verify that the battery is fully charged. Charge it again if necessary.
- Warm up the engine to the normal operating temperature.
- Stop the engine and allow it to cool off for about 10min.
- Perform FUEL PRESSURE RELEASE . Leave the fuel pump relay removed.
- Remove the spark plugs.
- Disconnect the ignition coil connector.
- Connect a compression gauge into the No.1 spark plug hole.
- Fully depress the accelerator pedal and crank the engine.
- Record the maximum gauge reading.
- Inspect each cylinder as indicated above.
- If the compression in one or more cylinders is low or the compression difference between cylinders exceeds the maximum, pour a small amount of clean engine oil into the cylinder and check the compression again.
- If the compression increases, the piston, piston rings, or cylinder wall may be worn and overhaul is required.
- If the compression stays low, a valve may be stuck or improperly seated and overhaul is required.
- If the compression in adjacent cylinders stays low, the cylinder head gasket may be damaged or the cylinder head is distorted and overhaul is required.
- Disconnect the compression gauge.
- Connect the ignition coil connector.
- Install the fuel pump relay.
- Install the spark plugs.
Tightening Torque
15-22 N.m {1.5-2.3 kgf.m, 11-16 ft.lbf}