Generac Power Systems GP Series Diagnostic Repair Manual page 50

Section 5 Engine Diagnostic Tests
b. If voltage measured greater than 12.5 VDC,
but less than 16 VDC, go to Step 4.
Set DMM to measure AC Volts and check for
4.
voltage on two yellow wires coming from the
engine stator coil.
a. If voltage measured less than 26 VAC, repair
wire/terminal if compromised and/or replace
the engine stator coil.
b. If voltage measure greater than 26 VAC, go to
Step 5.
Set DMM to measure DC Volts and check for
5.
voltage on the red wire coming from the voltage
regulator/rectifier.
a. If voltage measured less than 13.0 VDC,
replace the 10A Fuse (F3).
b. If voltage measured less than 13.0 VDC after
replacing the fuse, replace the voltage
regulator/rectifier.
c. If voltage measured greater than 13.0 VDC,
but less than 16 VDC, go to Step 6.
Set DMM to measure DC volts. Disconnect voltage
6.
regulator/rectifier from the engine stator coil and
check for voltage at the battery positive terminal.
a. If voltage measured other than static battery
voltage, replace diode/harness.
Test 22 – Testing Fuel Pump (FP)
General Theory
When the ECM activates the main power relay (MPR)
battery voltage (+) is delivered to the fuel pump relay
(FP) through fuse F2. The ECM also provides the ground
for the FP in the KSS—Key On and KSS—Key Start
positions. When the key is set to the ON position, the fuel
pump will run momentarily to pressurize the fuel system.
When the generator is running, the fuel pump provides
necessary pressure to the fuel injector to maintain a
running condition.
IMPORTANT NOTE: See
wires with test probes. Use needle multimeter test
probes (Generac P/N A0000683522) to back probe the
wires at the connection.
Figure 5-80. Needle Multimeter Test Probes
NOTE: During this procedure, battery voltage must be a
minimum of 12.5 VDC.
44
Figure 5-80. Do not pierce
010993
Procedure – Testing Circuit
NOTE: During these tests, the engine will not be running.
NOTE: The fuel pump fuel filter must be submerged in
fuel in order for fuel to be pressurized in the system.
Set the key switch to the ON position and listen for
1.
the fuel pump to run (hum or buzz momentarily).
a. If fuel pump does not run, go to Step 2.
b. If fuel pump runs, check fuel level.
c. If fuel level is sufficient, remove the pump
cover, remove the screws, lift the pump out of
the tank and check for contamination and/or
blockage of the fuel pump fuel filter. Clean fuel
filter or replace fuel pump. Repeat Step 1.
See Figure 5-81. Set key switch to the KSS—Key
2.
Off position. Remove the cover from the fuel pump
and disconnect the fuel pump connector and the
48-pin ECM harness connector, observing the
integrity of the wires and the connections.
Figure 5-81. Fuel Pump Connector
a. If the fuel pump wires, harness connector or
fuel pump
compromised or damaged, repair or replace.
b. If the fuel pump wires, harness connector or
fuel pump connector itself appears okay, go to
Step 3.
See Figure 5-82. Reconnect the fuel pump
3.
harness connector and verify proper operation of
the fuel pump circuit by back probing between the
black wire (A) and the red wire (B) at the fuel pump
connector to monitor voltage. Set the key switch to
the KSS—Key On position. Battery voltage should
be measured.
B
Figure 5-82. Fuel Pump Connector Test Points
connector itself appears
A
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