Generac Power Systems GP Series Diagnostic Repair Manual page 48

Section 5 Engine Diagnostic Tests
c. shorts to ground
Keep CONN1P Connector disconnected.
4.
Reconnect the ECM connector.
5.
Verify 12 VDC on both Wires 14C on the ECM side
6.
of the CONN1P Connector (coming from the
ECM).
Set key switch to the KSS—Key Start position to
7.
crank engine.
Verify 12 VDC is present on both Wires 14C while
8.
cranking.
Results
If Procedure A, B and C failed, repair or replace
1.
faulty component(s).
If there is no voltage on Wire 14C per Procedure D
2.
and all other wires pass testing between the
CONN1P Connector and the ECM, verify ECM is
correctly powered and grounded.
If ECM is correctly powered and grounded, test
3.
MPR.
Primary resistance (measured through
coil pins 14C and 451–452)
Secondary resistance (451–452 mea-
sured to any primary coil terminal)
NOTE: Before replacing ignition coil, check flywheel
crankshaft position sensor (CKP).
Flywheel Key
In all cases, the flywheel's taper is locked on the
crankshaft taper by the torque of the flywheel nut. A
keyway is provided for alignment only and theoretically
carries no load.
If flywheel key becomes sheared or even partially
sheared, ignition timing can change. Incorrect timing can
result in hard starting or failure to start.
Test 19 – Troubleshooting Oil
Pressure Switch (OPS)
If the engine cranks and starts, then shuts down within
about 5 (five) to 10 (ten) seconds with a Shutdown-Alarm
Low Oil Pressure, the cause may be one or more of the
following:
• Check malfunction indicator lamp (MIL)
• Low engine oil level.
•
Low oil pressure.
• Defective oil pressure switch.
• A wiring harness problem with Wire 14C or Wire
566.
NOTE: Oil pressure switch is Normally Open (N.O.) with
no oil pressure.
42
0.85–1.2
Ohm
11.5–18 k
Ohm
(Fault codes 6-1)
Figure 5-79. Oil Pressure Switch
Procedure
Measure the voltage of Wire 566 from the OPS
1.
switch to ECM.
a. Set a DMM to measure DC voltage.
b. Connect negative meter lead to battery
negative and connect positive lead to OPS
terminal with Wire 566 connected.
c. Start the generator
d. Observe the voltage of Wire 566.
e. If the voltage of Wire 566 shows 12 VDC once
the engine builds oil pressure, the OPS is
good.
NOTE: An intermittent oil pressure problem may still be
present and should be checked with a mechanical gauge
as in Step 4.
Check engine crankcase oil level. If necessary, add
2.
the recommended oil to the dipstick FULL mark.
DO NOT OVERFILL ABOVE THE FULL MARK.
With oil level correct, try starting the engine.
3.
a. If engine still cranks and starts, but then shuts
down, go to Step 4.
b. If engine cranks and runs normally, discontinue
tests.
Do the following:
4.
a. Disconnect Wire 566 and Wire 14C from the
OPS switch terminals. Remove the switch and
install an oil pressure gauge in its place.
b. Start the engine while observing the oil
pressure reading on the gauge.
c. Note the oil pressure.
(1) Normal oil pressure is approximately 35-
40 psi with engine running. If normal oil
pressure is indicated, go to Step 5 of this
test.
(2) If oil pressure is below about 4.5 psi, shut
engine down immediately. A problem
exists in the engine lubrication system.
NOTE: The oil pressure switch is rated at 10 psi.
015040
Diagnostic Repair Manual