Backfire Symptom - Mercury MerCruiser MCM 454 Mag MPI Service Manual

FUEL INJECTION SYSTEM TROUBLESHOOTING
Dieseling, Run-On Symptom (Continued)
7

Backfire Symptom

Step
Definition: Fuel ignites in the intake manifold, or in the exhaust system, making loud
popping noise.
1
2
3
4
5
6
Index
Page 5D-30
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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 sys-
tem.
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 flame arrestor for proper
installation.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for proper fuel pressure.
Refer to Table A-4 in "General Sys-
tem Diagnostics" section.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
Check the injector connections. If any of
the injectors are connected to an
incorrect cylinder, correct as necessary.
Was a problem found?
1. Check fuel injectors.
Refer to Injector Balance Test in
"General System Diagnostics" sec-
tion.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
SERVICE MANUAL NUMBER 23
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
Go to OBD
System
-
Check
Go to OBD
System
-
Check
90-861326--1 MARCH 1999
Contact
MerCruiser
Customer
Service
No
Go to OBD
System Check
Go to Visual/
Physical
Check
Go to Step 4
Go to Step 5
Go to Step 6
Go to Step 7