Mercury MerCruiser MCM 454 Mag MPI Service Manual page 577

FUEL INJECTION SYSTEM TROUBLESHOOTING
Detonation/Spark Knock Symptom (Continued)
12
13
14
15
Index
Page 5D-18
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1. Check for ECT sensor being shifted
in value.
2. Check for proper output voltage of
the TP sensor at closed throttle and
wide open throttle. Also check
throttle linkage for sticking, binding
or worn.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for the following Engine
Mechanical problems:
Low compression.
Low oil level.
Excessive oil in the combustion
chambers due to valve seals leak-
ing.
Worn or incorrect camshaft.
Proper valve timing/valve train prob-
lem.
Combustion chambers for exces-
sive carbon build up.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Remove excessive carbon buildup
with a top engine cleaner.
Refer to instructions on top engine
cleaner can.
2. Re-evaluate engine performance. Is
detonation still present?
1. Review all diagnostic procedures
within this table.
2. If all procedures have been com-
pleted and no malfunctions have
been found, review/inspect the fol-
lowing:
Visual/physical inspection.
Scan tool data.
All electrical connections within a
suspected circuit and/or system.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
SERVICE MANUAL NUMBER 23
Go to OBD
System
- Go to Step 13
Check
Go to OBD
System
Go to Step 14
-
Check
Go to Step Go to OBD
-
15 System Check
MerCruiser
Go to OBD
Customer
System
-
Check
90-861326--1 MARCH 1999
Contact
Service