Test 74 - Check And Adjust; Ignition Magnetos - Generac Power Systems 10 kW LP Repair Manual

sEctioN 4.4
DiaGNostic tEsts
WIRE 18 CONNECTION
Figure 32. Wire 18 Connection 10-20 kW Units
2. Depending on engine type, do the following:
a. On V-twin units, remove Wire 56 from the
Starter Contactor Relay (SCR). Using a jumper
lead, jump 12 VDC from Wire 15B at TB1
(Customer Connection) to the terminal on the
SCR from which Wire 56 was removed. The
generator will start cranking. As it is cranking,
repeat Test 70. Reconnect Wire 56 when done.
b. On single cylinder units, connect a jumper lead
from the stud to which Wire 56 is connected
on the Starter Contactor (SC) and 12 VDC
Wire 15B at TB1 (Customer Connection). The
generator will start cranking. As it is cranking,
repeat Test 70.
WIRE 18
CONNECTION
Figure 33. Wire 18 Connection 8 kW Units
3. If spark now occurs with Wire 18 removed, check for
a short to ground. Remove the J1 Connector from the
circuit board.
4. Set a VOM to measure resistance. Connect one test lead
to Wire 18 (disconnected in Step 1). Connect the other
test lead to a clean frame ground. INFINITY should be
measured.
5. Reconnect the J1 Connector to the circuit board.
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Part 4
RESULTS:
1. If INFINITY was not measured in Step 4, repair or replace
shorted ground Wire 18 between the J1 Connector from
the circuit board to the stud or bullet connector.
2. If INFINITY was measured in Step 4, replace the circuit
board and retest for spark.
3. If ignition spark still has not occurred, proceed to Test 74.
teSt 74 – check and adjuSt iGnition
maGnetoS
DISCUSSION:
In Test 70, a spark tester was used to check for
engine ignition. If sparking or weak spark occurred,
one possible cause might be the ignition magneto(s).
This test consists of checking ohm values across the
primary and secondary windings of the magneto and
adjusting the air gap between the ignition magneto(s)
and the flywheel. The flywheel and flywheel key will
also be checked during this test. A diode is installed
before the primary winding inside the coil. This is
done to inhibit a spark occurring on both magnetos at
the same time.
PROCEDURE: TESTING MAGNETOS V-TWIN ONLY
1. Disconnect the J1 connector from the printed circuit
board.
2. Disconnect spark plug wires from the spark plugs on
cylinder one and two.
3. Set VOM to measure resistance.
4. Connect the positive (red) meter lead to the bolt connec-
tor where Wire 18 was disconnected in Step 1. Connect
the negative (black) meter lead to a clean frame ground.
A resistance of approximately 300K ±10K ohms should
be measured. This reading is the primary winding of
both coils in parallel.
5. Connect the positive meter lead to the spark plug
wire and connect the negative meter lead to a clean
frame ground. Approximately 14K ±3 ohms should be
measured. This reading is the secondary winding of
both coils in parallel. If INFINITY, or a low or high ohm
reading is measured, replace the magnetos.
6. Connect the negative (black) meter lead to the bolt
connector where Wire 18 was disconnected in Step 1.
Connect the positive (red) meter lead to the spark plug
wire on cylinder number two. The meter should indicate
INFINITY. This step is testing the diodes in both magnetos
to ensure they are still functioning.
7. Repeat Step 6 on cylinder two. If INFINITY is not
measured, replace the magnetos.
note: it is recommended to replace magnetos
in pairs.
DC CONTROL