Detonation/Spark Knock Symptom - Mercury MerCruiser MCM 454 Mag MPI Service Manual

FUEL INJECTION SYSTEM TROUBLESHOOTING
Lack of Power, Sluggish or Spongy Symptom (Continued)
18
19

Detonation/Spark Knock Symptom

Step
Definition: A mild to severe ping, usually worse under acceleration. The engine makes
sharp metallic knocks that change with throttle opening.
1
2
3
4
Index
Page 5D-16
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1. Check for excessive resistance on
the bottom of the boat such as dirt,
barnacles, etc.
2. Check for proper propeller size and
pitch for that application.
3. If a problem is found, repair as
necessary.
Was a problem found?
1. Review all diagnostic procedures
within this table.
2. When all procedures have been
completed and no malfunctions are
found, review/inspect the following:
Visual/physical inspection.
Scan tool data.
All connections within a suspected
circuit and/or system.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
Action
Was the "On-Board Diagnostic" (OBD)
System Check performed?
Was visual/physical check performed?
1. Check base timing.
Refer to Ignition Timing Set Proce-
dure in the Distributor Ignition sec-
tion.
2. If a problem is found, repair as
necessary.
Was a problem found?
1. Check for proper operation of
Ignition Control (IC) circuit and the
Knock Sensor (KS) circuit.
2. If a problem is found, repair as
necessary.
Was a problem found?
SERVICE MANUAL NUMBER 23
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Value(s) Yes
Go to Step 2
-
- Go to Step 3
Go to OBD
System
-
Check
Go to OBD
System
-
Check
90-861326--1 MARCH 1999
Go to Step 19
Contact
MerCruiser
Customer
Service
No
Go to OBD
System Check
Go to Visual/
Physical
Check
Go to Step 4
Go to Step 5