FUEL INJECTION SYSTEM TROUBLESHOOTING
SERVICE MANUAL NUMBER 23
Page 5D-18
90-861326--1 MARCH 1999
Detonation/Spark Knock Symptom (Continued)
12
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?
-
Go to OBD
System
Check
Go to Step 13
13
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?
-
Go to OBD
System
Check
Go to Step 14
14
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?
-
Go to Step
15
Go to OBD
System Check
15
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?
-
Go to OBD
System
Check
Contact
MerCruiser
Customer
Service
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