Cylinder Contribution Tests

PURPOSE
To test individual power cylinders and injectors to determine if all are contributing equally to engine performance. This is a test performed by the Powertrain Control Module (PCM) after a standard Key On Engine Running (KOER)test is performed.

Connecting Test Equipment:

RECOMMENDED PROCEDURE
- Perform a standard KOER test. Note pre-conditions for test.
- After the PCM performs the step tests the cylinder contribution test will automatically start.
- The PCM will alternately cut off and then overfuel each cylinder and measure the change in fuel demanded by the remaining cylinders. A non-contributing power cylinder will have little effect on idle quality during this test.
- Code 51 through code 58 will be displayed during this test to indicate to the operator which cylinder is being tested (the last digit indicates the cylinder).
- At the end of this test codes 51 through 58 will be displayed to indicate which cylinders have been tested and either a PASS will be generated (111) or a code 941 through 948 will be generated (last digit indicates cylinder) to indicate the cylinder that failed this test.
- If any cylinder fails this test, perform a crankcase pressure test to verify base engine condition.

NOTE: The engine will operate at an elevated low idle speed and will run rough during this test.

POSSIBLE CAUSES
Failing this test could indicate mechanical engine problems such as broken compression rings, leaking or bent valves, bent push rods, bent connecting rods.

- Perform a crankcase pressure test to verify base engine condition.
- Remove the valve cover and inspect the valve train to determine valve train condition.
- Remove an injector, measure to the top of the piston at TDC and compare it to an adjacent cylinder to determine if the rods are bent.

If the base engine condition meets specifications, the injector may not be functioning correctly and will need replacement. The solenoid and wiring should have been checked in earlier tests. If the KOEO Injector Buzz Test was skipped, go back to perform that test before proceeding.

TOOLS REQUIRED
Rotunda Super STAR II tester 007-0041B