Mercury MerCruiser Service Manual page 83

Step
1 Was the Visual/Physical Check completed?
2 Did the onboard diagnostic (OBD) system check complete?
Is the engine propped to operate in the recommended
3
operating RPM range?
Check the spark plugs for:
• Proper type (refer to Section 1C ‑ Maintenance)
4
• Proper gap (refer to Section 1C ‑ Maintenance)
• Damage
Was a problem found?
Check the spark plug wires for continuity or damage.
5
Was a problem found?
• Check for contaminated fuel.
• Check fuel filters and the water‑separating fuel filter.
6
• Check for poor fuel quality and improper octane rating.
Was a problem found?
Check for proper fuel pressure while the condition exists.
7
Was a problem found?
Is the engine operating above the normal temperature
8
range?
Check for obvious overheating issues:
• Loose serpentine belt
• Faulty or incorrect seawater pump
9
• Restriction in the cooling system
• Faulty or incorrect thermostat
Was a problem found?
10
Is a scan tool being used?
Check for an ECT sensor shifted in value.
With the engine completely cool, measure the resistance of the
ECT sensor.
Refer to PCM 112–Section 3A ‑ Component testing Sensor.
11
Compare the approximate temperature of the ECT sensor to an
accurate reading of ambient air temperature.
Are the readings similar?
Check for an ECT sensor shifted in value.
Using the scan tool with the engine completely cool, compare
12 the ECT sensor temperature with an accurate reading of
ambient air temperature.
Are the temperatures within 5.5° C (10° F) of each other?
13 Check for loose fasteners, sensors, and connections.
Check for the following:
• Low compression
• Leaking cylinder head gaskets
14
• Worn camshaft
• Improper valve timing or valve train problem
• Restricted exhaust system
Was a problem found?
90-8M0099748 eng DECEMBER 2015
Action Yes
Go to step 2.
Go to step 3.
Go to step 4.
Replace the problem spark
plugs with those specified for
the application.
Replace the questionable
spark plug wire.
Retest the system.
Use known good fuel.
Replace the fuel filters.
Go to Chart T3.
Go to step 9.
Repair or replace.
Retest the system.
Go to step 12.
Go to step 13.
Go to step 13.
Tighten and secure.
Engine mechanical problem,
refer to Section 3 ‑ Engine
Mechanical.
© 2016 Mercury Marine
Troubleshooting
No
Go to the Visual/Physical
Check.
Connect the CDS G3
service tool and scan for
faults.
Check propping
procedures.
Go to step 5.
Go to step 6.
Go to step 7.
Go to step 8.
Go to step 10.
Go to step 10.
Go to step 11.
Replace the ECT sensor.
Retest the system.
Replace the ECT sensor.
Retest the system.
Go to step 14.
Go to step 15.
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