Generac Power Systems IM Series - Manual (Page 18)

Step 6- Check Engine Ignition System
Test Procedure:- Refer to section in this Manual entitled
ENGINE TROUBLESHOOTING. Also refer to the EN­
GINE SERVICE MANUAL, if necessary.
Test Results:
A. Ignition System checks GOOD: Go to Step 7
B. Ignition System checks BAD: Repair or replace defec­
tive component(s) mas necessary
Step 7- Test Choke Module
NOTE: The following procedure will test the Wire 14
diode, the field boost diode, and the field boost
resistor. To test these components. It Is recom
mendecf that a Volt-Ohm-Mllllammeter having a
DIODE TEST capability be used. The solid state cir­
cuit that regulates automatic choke opening and
closing cannot be tested In the field. That circuit will
be tested In Step 8 by observing choke operation,
Test Procedure:- See Figure 7. Disconnect ail wires from
Choke Moduie terminals to prevent interaction. Then,
proceed as follows:
1. To test the Wire 14 diode, connect one VOM test lead
to Terminal 3 of the Choke Module; connect second test
lead to ,Terminal 1. Observe the meter reading. Then,
reverse the test leads (reverse the d-c polarity) across
those Choke Module terminals and again observe the
reading. At one polarity, the VOM should read infinity. At
the opposite polarity, the VOM should indicate the for­
ward resistance of the 6 amp, 100 volts diode in the Wire
14 circuit. If using a VOM having the diode test feature,
allowable voltage drop across the diode is 0.6 to 0.8 volt.
2. To test the Field Boost diode and resistor, connect one
VOM test lead to Choke Module Terminal 3, the second
test lead to Terminal 2. Note the meter reading. Then,
reverse the test leads (reverse polarity) and again ob­
serve the VOM reading. At one polarity, the meter should
indicate infinity. At the opposite polarity, the meter should
read the forward resistance of the diode plus the resis­
tance of the Field Boost Resistor. If a VOM having the
diode test feature is used, allowable voltage drop will be
0.6 to 0.8 volts PLUS the voltage drop across the resis­
tor.
NOTE: The Field Boost Resistor is rated 47 ohms at
2 watts (plus or minus 10%). The Field Boost diode
Is rated 1 amp at 600 volts._________________________
3. The Choke Module circuit includes a metal oxide Varis­
tor, rated 22 volts, 0.6-0.8 Joule. There is no good method
of testing a Varistor in the field. Typically, when a Varis­
tor fails it will overheat and melt. Inspect the Choke
Module- if evidence of overheating and melting is ob­
served, replace the Choke Module.
Test Results:
A. All Choke Module tests are GOOD: Go to Step 8
B. Choke Moudle tests BAD: Replace Choke Module
Figure 7. Choke Module
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Step 8- Check Automatic Choke Operation
Test Procedure;- See Figure 8. Crank engine while ob­
serving choke operation. The Choke Solenoid CS should
pull in to close choke for about 0.2-0.4 seconds, should
then de-energize to open choke for about 2 seconds. This
cyclic action should occur while the engine is cranking. If
Choke Solenoid does not actuate, check for binding. Also
check for proper choke adjustment (see ADJUSTMENTS
section).
Test Results:
A. Choke operation checks GOOD, engine still won’t
start: Go to Step 9
B. Choke operation checks BAD: Try adjusting choke- if
it still does not operate, replace Choke Module
Step 9- Check Engine Compresslon/Condition
Test Procedure:- Refer to section entitled ENGINE
TROUBLESHOOTING. If necessary, also refer to the EN­
GINE SERVICE MANUAL.
Test Results:
A. Engine^Checks GOOD: Go to Step 10
B. Engine checks BAD; Repair/replace engine as neces­
sary
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