Yamaha F350B - Checking the Low-Pressure Fuel Pump and High-Pressure Fuel Pump

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Fuel control unit and component
Checking the low-pressure fuel pump
and high-pressure fuel pump
1. Check:
• Fuel pump operation (using the YDIS “Sta-
tionary test”)
No operation sound  Check the fuel
pump input voltage.
2. Measure:
• Low-pressure fuel pump input voltage
Out of specification  Check the wire har-
ness for continuity.
a. Disconnect the low-pressure fuel pump
coupler “a”.
b. Turn the “POWER” switch to ON, and then
measure the input voltage between the
low-pressure fuel pump coupler terminal
and ground.
c. Turn the “POWER” switch to OFF.
3. Measure:
• High-pressure fuel pump input voltage
Out of specification  Check the wire har-
ness for continuity.
a. Disconnect the high-pressure fuel pump
coupler “a”.
b. Connect the tester probes to the terminals
of the high-pressure fuel pump coupler “a”,
and then measure the input voltage within
5 seconds after turning the “POWER”
switch to ON.
c. Turn the “POWER” switch to OFF.
4. Measure:
• Fuel pump resistance
Out of specification  Replace.
a. Measure the resistance of the fuel pump
motors.
Input voltage
12 V
Red/Yellow (R/Y)–Ground
Input voltage
12 V
Red (R)–Blue (L)
R/Y
a
Low-pressure fuel pump
Resistance (reference data)
0.5–4.0 
High-pressure fuel pump
Resistance (reference data)
0.2–3.0 
A. Low-pressure fuel pump
B. High-pressure fuel pump
LR
a
A
B