Compression Check: Testing and Inspection

Compression testing

Special tools: 9689, 115 8263, 175 8540

Ignition system





WARNING: The ignition system operates at high power, with dangerous voltages in both the low-tension and high-tension circuits.

Dangerous voltage levels occur in all parts of the ignition system, including connectors and similar fittings.





Measure compression at full throttle with engine hot
Normal value: 0.9-1.1 MPa (131-160 psi)

NOTE: Above value applies when engine is hot, throttle is fully open and engine is turned at 4.2-5.0 r/s (250-300 rpm) using starter motor.





Disconnect:
- lead from terminal 1 on ignition coil (to prevent flashover to electrical system wiring)
- injector connectors (to prevent flooding of engine and dilution of engine oil)





Remove:
- ignition lead cover plate
- ignition leads from plugs
- plugs from cylinder head

Clean spark plug wells as required before removing plugs. Check condition of plugs.

NOTE: Always grip ignition leads by caps when removing to avoid damage to leads.





Lock throttle in fully open position
Use tool such as screwdriver for this purpose.





Connect starter switch
Use special tool 115 8263-4.

Connect switch in series with alternator (+) and service point on left-hand wheel housing.





Measure compression
Use compression tester 9689 and extension sleeve 115 8540.

Measure compression in all cylinders.





Disconnect/remove:
- starter switch
- throttle 'lock'

Check that throttle cable is seated in pulley groove.





Reconnect:
- injector connectors
- lead to terminal 1 on ignition coil





Install spark plugs
Screw in each plug until sealing ring is in firm contact with cylinder head.

Alt. 1
Tighten new plugs through further 90°.
Tighten used plugs through further 30°.

Alt. 2
Tightening torque 25 ± 5 Nm (18.5 ± 4 ft.lb)





Install:
- ignition leads (in correct firing order)
- ignition lead cover plate