Chart S9: Backfire - Mercury MerCruiser Service Manual

Troubleshooting
Step
1 Was the Visual/Physical Check completed?
Did the onboard diagnostic (OBD) system check
2
complete?
Check for proper fuel pressure while the condition
3 exists.
Was a problem found?
Check the fuel injectors.
4
Was a problem found?
Check for obvious overheating issues:
• Loose serpentine belt
• Faulty or incorrect seawater pump
5
• Restriction in the cooling system
• Faulty or incorrect thermostat
Was a problem found?
Check the fuel pump relay for proper operation.
6
Was a problem found?
Review all of the procedures in this table. If all procedures have been completed and no problem found, inspect the
following:
7
• CDS G3 scan tool data
• All of the electrical connections within a suspect circuit or system

Chart S9: Backfire

Definition: Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.
Step
1 Was the Visual/Physical Check completed?
2 Did the onboard diagnostic (OBD) system check complete?
Check the flame arrestor for dirt, damage, or any restriction.
3
Was a problem found?
• Check for contaminated fuel.
• Check fuel filters and the water‑separating fuel filter.
4
• Check for poor fuel quality and improper octane rating.
Was a problem found?
Check for proper fuel pressure while the condition exists.
5
Was a problem found?
Check the fuel injectors.
6
Was a problem found?
Check the spark plug wires for open circuits, cracks in the
insulation, or improper seating of the terminals at the spark plugs
7
and coil tower.
Was a problem found?
Check the ignition coil for cracks or carbon tracking.
8
Was a problem found?
Check for adequate spark at all of the spark plugs.
9
Was adequate spark present?
Page 1D-18
Action
Action
© 2016 Mercury Marine
Yes
Go to step 2.
Go to step 3.
Go to Chart T3.
Repair or replace the faulty
injector.
Repair or replace.
Retest the system.
Repair or replace.
Retest the system.
Yes
Go to step 2.
Go to step 3.
Clean or replace the flame
arrestor.
Use known good fuel.
Replace the fuel filters.
Go to Chart T3.
Repair or replace the faulty
injector.
Locate and repair or replace.
Retest the system.
Repair or replace the ignition
coil.
Retest the system.
Go to step 10.
90-8M0099748 eng DECEMBER 2015
No
Go to the Visual/Physical
Check.
Connect the CDS G3 service tool
and scan for faults.
Go to step 4.
Go to step 5.
Go to step 6.
Go to step 7.
No
Go to the Visual/
Physical Check.
Connect the CDS G3
service tool and scan
for faults.
Go to step 4.
Go to step 5.
Go to step 6.
Go to step 7.
Go to step 8.
Go to step 9.
Go to Chart T4.