Generac Power Systems GP Series Diagnostic Repair Manual page 42

Section 5 Engine Diagnostic Tests
Introduction
Perform the Diagnostic Tests in this section in
conjunction with the Diagnostic Flow
numbers in this chapter correspond to numbered tests in
the flow charts.
NOTE: Test procedures in this manual are not
necessarily the only methods for diagnosing the condition
of components and circuits. All possible methods that
might be used for system diagnosis have not been
evaluated. If any diagnostic method is used other than
the method presented in this manual, the technician must
be sure that neither personal safety nor product safety,
will be endangered by the procedure or method selected.
Test 11 – Check Fuse(s)
General Theory
See Figure 5-62. Two fuses protect the wiring from a
short circuit.
Figure 5-61. Fuses F1 and F2
Figure 5-62. Typical Fuse
See Figure 5-63. Fuse F1 (A) and Fuse F2 (B) are
located 0n the back end of the control panel.
A
B
Figure 5-63. Fuses F1 and F2 Location
36
Procedure
Remove and inspect fuse(s).
Charts. Test
Results
If fuse element melted open, replace fuse with an
identical size fuse. If fuse is good, refer to flow chart.
Test 12 – Checking Battery and
Cables
General Theory
Battery power is used to crank the engine. Low or no
battery voltage can result in failure of the engine to crank.
The battery charging circuit is not designed to recharge a
dead battery. As well, if there is a loose connection or
corrosion associated with a wire (positive or negative),
battery voltage may be present, but due to high
resistance, will not allow current to flow.
Electrical voltage drop varies according to current flow.
Voltage drop cannot be measured unless the circuit is
operated so current can flow through it. A crank attempt
will need to be performed to properly measure voltage
drop. This test will determine whether the battery, battery
cables, or both are at fault.
Procedure A – Perform Starter Circuit Voltage
Drop Test
Set a digital multimeter (DMM) to measure DC volt-
1.
age.
015037
Connect the red meter test lead to the positive
2.
battery post and connect the black meter test lead
to the negative battery post.
a. If battery voltage is 12.1 VDC or below,
b. If battery voltage is 12.4 VDC or above,
010865
To inhibit any possible startup, turn off the fuel
3.
source and ground the ignition control wire. (refer
to applicable schematic)
Refer to battery post and starter connections in
4.
Figure 5-64
voltage drop test as indicated.
Turn engine switch to START. Allow the engine to
5.
crank
measurement.
Record voltage readings from test points V1, V2,
6.
V3 and V4. Although resistance-free connections,
wires and cables would be ideal, most of them will
contain at least some voltage drop. The maximum
voltage readings should be as follows:
015038
a. 0.00-0.10 VDC across a connection or battery
recharge the battery and retest.
proceed to next step. (For this test, battery
voltage should be at least 12.4 VDC)
and Figure 5-65
long enough to
post (V4).
Diagnostic Repair Manual
then perform a
obtain a steady