Yamaha F225F Service Manual page 157

Symptom 1: Unstable engine idle speed, poor acceleration, poor performance, or limited
engine speed.
Symptom 2
Spark plug does not
spark (some cylinders)
Fuel pressure is low
Fuel not supplied (some
cylinders)
Compression pressure
is low
Cause
Spark plug malfunction
Short, open, or loose connec-
tion in ignition coil circuit
Ignition coil malfunction
Engine ECM malfunction
—
Fuel leakage
Pressure regulator malfunction Check the pressure regulator.
Clogged fuel filter
High-pressure fuel pump mal-
function
Fuel injector malfunction
Short, open, or loose connec-
tion in fuel injector circuit
Clogged fuel injector filter
Engine ECM malfunction
—
Improper valve timing
Compression leakage
Troubleshooting the power unit
Checking step
Check the ignition spark.
Check the spark plug.
Measure the ignition coil input voltage.
Check for wiring continuity between the
ignition coil and engine ECM.
Check for wiring continuity between the
ignition coil and main relay.
Exchange the ignition coil with a different
one, and then check the ignition spark.
Replace the engine ECM.
Measure fuel pressure.
Check the fuel leakage.
Check the fuel filter for dirt and obstruc-
tions.
Measure the high-pressure fuel pump
resistance.
Check the fuel injector operation using
the YDIS.
Measure the fuel injector resistance.
Measure the fuel injector input voltage.
Check for wiring continuity between the
fuel injector and main relay.
Check for wiring continuity between the
fuel injector and engine ECM.
Replace the fuel injector.
Replace the engine ECM.
Measure the compression pressure.
Check the valve timing.
Check the timing belt.
Check the valve for bends and sticking.
Check the piston and piston rings for
damage.
Check the cylinder for scratches.
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