Mercury MerCruiser MCM 454 Mag MPI Service Manual page 660

SERVICE MANUAL NUMBER 23
Chart A-3 (2 of 5): Engine Cranks But Will Not Run
DIAGNOSTIC AIDS:
This chart assumes that battery voltage and engine cranking speed are OK, and there is
adequate fuel in the tank.
Water or foreign material in fuel system can cause a no start.
A defective MAP sensor may cause a no start or a start and stall condition. To determine
if the MAP sensor is causing the problem, disconnect the electrical connector. The ECM will
then use a default value for the sensor. If the condition is corrected and the connections are
OK, then replace the sensor.
An intermittent may be caused by a poor connection, rubbed through wire insulation or a
wire broken inside the insulation. Check for the following items:
Poor connection or damaged harness. Inspect the ECM harness and connectors for
improper mating, broken locks, improperly formed or damaged terminals, poor terminal to
wire connection, and damaged harness.
If above are all OK, refer to "Hard Start" in "Troubleshooting" section.
Step
Index
90-861326--1 MARCH 1999
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Action
Was the "On-Board Diagnostic"
1
(OBD) System Check performed?
Disconnect Throttle Position (TP)
2 sensor.
Does The Engine Start?
1. Key "OFF" for minimum of 10
seconds.
2. Key "ON."
3
3. Listen for fuel pump to run.
Does Fuel Pump Run For 2
Seconds?
Crank engine for 1 second and
4 listen for fuel pump to run.
Does Fuel Pump Run?
Check for secondary
spark.
5
Is Adequate Spark Present At All
Cylinders?
Value(s)
–
Go to Step 2
–
Go to Step 14
–
Go to Step 4
–
Go to Step 5
ignition
–
Go to Step 6
GENERAL SYSTEM DIAGNOSTICS
Yes No
Go to OBD
System Check
Go to Step 3
Go to Chart A-4
Go to Step 9
Go to Chart A-7
Page 5E-67