Yamaha F150A Service Manual page 124

Symptom 2
Spark plug does not pro-
duce a 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
Pulser coil malfunction
High-pressure fuel line 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
Outboard motor troubleshooting
Checking steps
Check the ignition spark.
Check the spark plugs.
Measure the spark plug wire resistance.
Check for wiring harness continuity
between the ignition coil and the engine
ECM.
Check for wiring harness continuity
between the ignition coil and the main
relay
Measure the ignition coil input voltage.
Measure the ignition coil output peak
voltage.
Measure the ignition coil resistance.
Measure the pulser coil output peak volt-
age.
Measure the pulser coil resistance.
Measure the fuel pressure.
Check the pressure regulator.
Check the fuel filter for dirt and obstruc-
tions.
Check the high-pressure fuel pump.
Check the fuel injector operation using
the YDIS.
Measure the fuel injector resistance.
Measure the fuel injection volume.
Measure the fuel injector input voltage.
Check for wiring harness continuity
between the fuel injector and the main
relay.
Check for wiring harness continuity
between the fuel injector and the engine
ECM.
Replace the fuel injector.
Replace the engine ECM.
Check the timing belt.
Measure the compression pressure.
Measure the valve clearance.
Check the camshaft for damage.
Check the valve and valve seat for wear.
Check the piston and piston ring for
damage.
Check the cylinder for scratches.
4-13
See
page
5-21
7-25
0
5-21
A-4
1
A-4
5-21
2
5-21
5-21
3
5-22
5-22
6-5
4
6-5
6-43
5-18
5
5-17
5-17
6-32
6
5-17
A-2
7
A-2
6-30
8
7-28
7-17
7-1
7-1
9
7-35
7-41
7-43
10
7-61
7-64
A