Compression; Inspection - Mazda MX-5 1990 Workshop Manual

B
COMPRESSION
COMPRESSION
If the engine exhibits low power, poor fuel economy, or poor idle, check the following:
1. Ignition system (Refer to page G-17.)
2. Compression
3. Fuel system (Refer to page F-100.)
8-10
05UOBX-017
INSPECTION
1. Check that the battery is fully charged. Recharge it if neces-
sary. (Refer to page G-S.)
2. Warm up the engine to the normal operating temperature.
3. Turn the engine OFF.
4. Remove all spark plugs.
5. Disconnect the ignition coil connector.
6. Connect a compression gauge to the No.1 spark plug hole.
7. Fully depress the accelerator pedal and crank the engine.
S. Record the maximum gauge reading.
9. Check each cylinder.
Compression:
1,324 kPa (13.5 kg/cm
2
,
192 psi) • 300 rpm
Minimum:
932 kPa (9.5 kg/cm
2
,
135 pSi) • 300 rpm
Differential limit between cylinders:
196 kPa (2.0 kg/cm
2
,
28 psi)
10. If the compression in one or more cylinders is low, pour a
small amount of engine oil into the cylinder and recheck
the compression.
(1) If the compression increases, the piston, piston rings,
or cylinder wall may be worn.
(2) If the compression stays low, the valve may be stuck
or seating
imprope~ly.
(3) If the compression ih adjacent cylinders stays low, the
cylinder head gasket may be defective or the cylinder
head distorted.
11. Connect the ignition coil connector.
05UOBX-020
12. Apply antiseize compound or molybdenum-based lubricant
to the spark plug threads.
13. Install the spark plugs.
Tightening torque:
15-23 N·m (1.5-2.3 m-kg, 11-17 ft-Ib)