Mercury MerCruiser MCM 454 Mag MPI Service Manual page 576

SERVICE MANUAL NUMBER 23
Detonation/Spark Knock Symptom (Continued)
Index
90-861326--1 MARCH 1999
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1. Check for good ignition system
ground.
2. Check spark plugs for proper gap
and heat range.
5
3. If a problem is found, repair as
necessary.
Was a problem found?
1. Check for contaminated fuel.
2. Check for poor fuel quality and
proper octane rating.
6
3. If a problem is found, repair as
necessary.
Was a problem found?
1. Check for proper fuel pressure.
Refer to Table A-4 in "General Sys-
tem Diagnostics" section.
7
2. If a problem is found, repair as
necessary.
Was a problem found?
8 Is a scan tool being used?
If scan tool readings are normal ( Refer
to "Scan Tool Normal Specifications" in
this section) and there are no engine
9
mechanical faults, fill fuel tank with a
known high quality gasoline.
Is detonation present?
1. Check for obvious overheating
problems:
Loose water pump belt.
Faulty or incorrect water pump.
10 Restriction in cooling system.
Faulty or incorrect thermostat.
2. If a problem is found, repair as
necessary.
Was a problem found?
1. Check fuel delivery system items
that can cause an engine to run lean.
11
2. If a problem is found, repair as nec-
essary.
Was a problem found?
FUEL INJECTION SYSTEM TROUBLESHOOTING
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Go to OBD
System
-
Check
- Go to Step 9 Go to Step 10
Go to Step
-
10 System Check
Go to OBD
System
Go to Step 11
-
Check
Go to OBD
System
- Go to Step 12
Check
Go to Step 6
Go to Step 7
Go to Step 8
Go to OBD
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