Yamaha F150A Service Manual page 123

Symptom 2
Fuel not supplied
(all cylinders)
Compression pressure
is low
—
Symptom 1: Unstable engine idle speed, poor acceleration, poor performance, or limited
engine speed.
Symptom 2
Throttle valve does not
move properly
Cause
—
Clogged filter
Fuel leakage
High-pressure fuel pump mal-
function
Main relay malfunction
Short, open, or loose connec-
tion in high-pressure fuel pump
circuit
Fuel pump malfunction
Y-COP is locked.
Improper valve timing
Compression leakage
Intake air passage malfunction
Cause
Throttle valve malfunction
Throttle valves do not synchro-
nize.
Throttle link and throttle cable
are not installed properly.
Outboard motor troubleshooting
Checking steps
Measure the fuel pressure.
Check the fuel filter for dirt and obstruc-
tions.
Check the fuel line for leakage.
Check the high-pressure fuel pump oper-
ation using the YDIS.
Measure the high-pressure fuel pump
resistance.
Check the main relay.
Measure the high-pressure fuel pump
input voltage.
Check for wiring harness continuity
between the high-pressure fuel pump
and the main relay.
Check for wiring harness continuity
between the high-pressure fuel pump
and engine ECM.
Check the fuel pump for leakage.
Check the diaphragm for tears.
Check the camshaft.
Unlock Y-COP.
Check the timing belt.
Measure the compression pressure.
Check the valve for bends or sticking.
Check the piston and piston rings for
damage.
Check the cylinder for scratches.
Check the ISC valve for sticking.
Check the intake manifold and throttle
body for air leakage.
Checking steps
Check the throttle valve for proper move-
ment.
Synchronize the throttle valves.
Adjust the throttle link and throttle cable.
4-12
See
page
6-5
6-9
6-1
5-18
5-18
5-13
5-18
A-2
A-2
6-13
6-14
7-35
3-20
7-17
7-1
7-41
7-61
7-64
5-15
6-34
See
page
6-25
6-29
3-11
6-27