Mercury MerCruiser MCM 454 Mag MPI Service Manual page 590

SERVICE MANUAL NUMBER 23
Backfire Symptom (Continued)
Index
90-861326--1 MARCH 1999
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1. Check for proper operation of Igni-
tion Control (IC) circuit and the
Knock Sensor (KS) circuit.
7
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check integrity of the primary and
secondary wiring.
2. Check routing of the wiring.
3. Check condition of IC module,
8 pick-up coil, distributor cap, rotor
and spark plug wires.
4. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check ignition coil for cracks or car-
bon tracking.
9
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for proper ignition voltage
input to the ECM.
2. Check for intermittent open or short
to ground on the ignition voltage
10
input circuit to the ECM.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Remove spark plugs, check for wet
plugs, cracks, wear, improper gap,
burned electrodes or heavy depos-
its.
Refer to Distributor Ignition System
in "Description and System Opera-
tion" section.
11
NOTE: If park plugs are gas or oil fouled,
the cause of the fouling must be deter-
mined before replacing the spark plugs
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
- Go to Step 10
Check
Go to OBD
System
- Go to Step 11
Check
Go to OBD
System
- Go to Step 12
Check
Go to Step 8
Go to Step 9
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