Generac Power Systems NP-40G - Manual (Page 114)

Section 7.2- ENGINE DC CONTROL SYSTEM
Test 25- Isolate the CCG System
DISCUSSION:
If the engine starts, but then shuts down after
startup, a problem could exist In either the genera­
tor computer system or In the engine DC control
system. Refer to “CCG Circuit Board" on Pages
1.2-4 through 1.2-6.
This test will either eliminate the CCG system as
a cause of the shutdown problem or It will prove
that the problem Is In the CCG system.
TEST FIXTURE:
The CCG circuit board must be able to detect
certain electrical fault conditions and shut the en­
gine down. See "AUTOMATIC SHUTDOWNS" on
Page 1.2-5. For that purpose. Wire 18B Is routed
from the Engine Controller board to the CCG board.
This wire has a negative DC voltage applied to it
and shutdown will occur when CCG board action
connects the wire to ground.
To Isolate the CCG system as a cause of engine
shutdown requires that Wire 18B be disconnected
from the CCG circuit board. However, the CCG
board "knows" when the wire Is disconnected and
will attempt to stop the engine if such disconnec­
tion occurs. Because the wire is disconnected,
such a shutdown cannot occur. However, CCG
board action will result in incorrect engine speeds
if the wire Is disconnected.
For the above reason, a test fixture Is required
to simulate the negative DC voltage normally sup­
plied by Wire 18B. The test fixture consists of (a) a
9 volt battery, (b) a Ik resistor, and (c) necessary
wiring and connectors. The negative side of the
battery Is connected to "CONN8" of the CCG cir­
cuit board. Connect the positive side of the battery
to frame ground on the generator. See Figure 11.
Figure 11. CCG Board Test Fixture
3 4
Use 18 Gauge or
Instrument wire
1.9 volt alkaline battery
2. Battery Connector
3. Barrel Connector (3)
4. Resistor- Ik, 1/4 or 1/2 watt
5. Spade Lug
6. Grounding Clamp
PROCEDURE:
Connect the test fixture to the circuit board’s
"CONN8" terminal and to the negative (-) terminal
of a 12 volt battery. Connect the battery positive (+)
terminal to frame ground. Crank and start the en­
gine and observe its operation.
RESULTS:
1. If the engine starts and shuts down, check engine
oil level.
a. if oil level Is low, replenish as necessary.
b. If oil level is NOT low, go to Test 26.
2. If engine was shutting down after startup, but
does not shut down during this test, the problem is
In the CCG system. Go to Test 27.
Test 26- Test Oil Pressure Switch
DISCUSSION:
See Section 6.5, "ENGINE PROTECTIVE DEVICES".
TEST PROCEDURE:
See Section 6.5.
if necessary, connect an external oil pressure
gauge to the oil pressure switch port.
RESULTS:
1. Replace oil pressure switch if It Is defective or
repair Wire 85 circuit as necessary.
2. If oil pressure Is actually low as indicated by the
external gauge, see Section 5.1, "ENGINE OIL SYS­
TEM".
3. If oil pressure Is good and oil pressure switch Is
good, go to Test 28.
Test 27- Test CCG System
DISCUSSION:
If Test 25 indicated that engine shutdown or any
other problem was being caused by the CCG sys­
tem, this does not necessarily indicate a fault in the
CCG system. The CCG board may be dolno exactly
what it was designed to do, I.e., Initiate a shutdown
when a fault exists In the generator system. The
CCG board will shut the engine down on occurence
of one or more of the following faults:
1. Over-voltage.
2. Undervoltage (or overload).
3. Overspeed above 4500 rpm.
4. Zero current failure.
5. Converter failure.
6. Microprocessor failure.
NOTE: Also see “CCG Circuit Board“ on Pages
1.2-4 through 1.2-6.
Page 7.2-12