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Ignition
Troubleshooting without a Computer Diagnostic System (CDS)
Troubleshooting without the computer diagnostic system (CDS) is limited to checking resistance on some of the sensors.
Typical failures usually do not involve the PCM. Connectors, setup, or mechanical wear are most likely at fault.
•
Verify the ignition spark plug boots are securely installed (pushed in) onto the spark plugs.
•
The engine may not run or may not run above idle with the wrong spark plugs installed.
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Swap ignition coils to see if the problem follows the coil or stays with the particular cylinder.
IMPORTANT: Disconnecting a sensor while the engine is running may result in a fault recording in the PCM Fault History. Use
the CDS to view the PCM fault history when troubleshooting/repair is completed.
•
If all cylinders exhibit similar symptoms, the problem is with a sensor or harness input to the PCM.
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If problem is speed related or intermittent, it is probably connector or contact related. Inspect connectors for corrosion, loose
wires, or pins pushed back into the connector. Verify the connectors are properly seated.
•
Inspect the harness for damage: pinched or cut wires and chafing.
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Secure the grounds and all connections involving ring terminals. Apply Liquid Neoprene to all ring terminal connections.
Tube Ref No.
Liquid Neoprene
25
•
Inspect the fuel pump harness connector for corrosion, loose wires, or pins pushed back into the connector.
•
Check the fuel pump pressure.
•
Check the air compressor air pressure.
Troubleshooting with the Computer Diagnostic System (CDS)
The computer diagnostic system (CDS) is designed to help technicians diagnose and repair Mercury Marine 2 and 4 cycle engines.
Attach the diagnostic cable to the PCM diagnostic connector. This will enable the technician to monitor sensors, PCM data values,
and the real time status of the switches. Use the 3 m (10 ft.) extension cable between the CDS diagnostic connector and the PCM
adapter to monitor the engine system while at the helm.
The PCM program can help diagnose intermittent engine problems. It will record the state of the engine sensors and switches for
a period of time, and then can be played back to review the recorded information.
Refer to the computer diagnostic system reference manual for complete diagnostic procedures.
Computer Diagnostic System (CDS)
Extension Cable
Adapter Harness
Page 2A-10
Description
Where Used
All ring terminal connections
a -
Diagnostic terminal connector
a
39106
Order through SPX
84‑825003A 1
84‑822560A13
Part No.
92- 25711 3
90-8M0050731 MAY 2011
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Troubleshooting
