Yamaha MX775 - Checking the Low-Pressure Fuel Pump; Checking the High-Pressure Fuel Pump

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FUEL
FUEL PUMPS
CHECKING THE LOW-PRESSURE FUEL PUMP
1. Check:
• Fuel hose “1”
• Fuel delivery hose “2”
• Pulsar hose “3”
• Low-pressure fuel pump “4”
Cracks/damage  Replace.
2. Check:
• Low-pressure fuel pump operation
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a. Connect the manual vacuum pump (Pressure/vac-
uum tester) “1” to the pulsar hose “2”.
b. Place the container underneath the end of the fuel
delivery hose “3”.
c. Operate the manual vacuum pump (Pressure/vac-
uum tester) “1” and check that gasoline is flowing
out of the fuel delivery hose “3”.
d. If not, replace the fuel pump assembly.
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CHECKING THE HIGH-PRESSURE FUEL PUMP
1. Check:
• High-pressure fuel pump
Cracks/damage  Replace.
2. Check:
• Fuel pressure
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a. Disconnect the fuel injector pipe 1 “1” from the fuel
pump.
Refer to “REMOVING THE HIGH-PRESSURE
FUEL PUMP” on page 4-2.
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Pressure/vacuum tester:
YB-35956-B
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Cover fuel injector pipe 1 connections with a cloth
when disconnecting them. Residual pressure in the
fuel lines could cause fuel to spurt out when removing
the fuel injector pipe 1.
WARNING