Engine - Compression Test

86volvo01

SECTION GROUP NO.

21 117
DATE JANUARY 1986 RE:
COMPRESSION TEST


4-cyl. engines
THIS BULLETIN APPLIES TO THE U.S. AND CANADA. This information modifies the compression pressures listed in various "Specifications" and "Engine-Repairs and Maintenance" Service Manuals.


The main purpose of compression testing is to determine that sufficient compression is available for proper combustion. An important requirement is that the difference between individual cylinders within the same engine not be too great.



TESTING COMPRESSION (hot engine)

- Disconnect wire from terminal 1 A1 of ignition coil


CAUTION: If ignition coil terminal 1 wire is not disconnected on cars with LH-jetronic injection, ignition voltage sparkover may occur, which can damage ignition system control unit or Hall integrated circuit in the distributor.


- remove spark plugs



- measure compression A2

NOTE: Engine must be hot and throttle fully open with a starter motor cranking speed of 4.2-5.0 r/s (250-300 rpm)

Specification:

Minimum value 0.9 MPa (128 psi)

Max. difference between
cylinders of same

engine 0.2 MPa (28 psi)

- install spark plugs. Torque to 25 +/- 5 N-m (18 +/- 4 ft.lbs.)
Results may be influenced by:

- battery voltage (affects starter motor speed)
- tolerances in different measuring equipment
- carbon deposits in combustion chambers