Guardian 4721, Repair Manual, Page: 91 / 115

DC CONTROL
LIQUID COOLED
ENGINE UNITS
SECTION 4.4
DIAGNOSTIC TESTS
PART 4
Page 87
PROCEDURE:
In the case of LP (propane) gas, some supply tanks
will be equipped with a gauge that indicates when the
tank is low on fuel.
For natural gas systems, the gas distribution compa-
ny will usually provide piping from the main transmis-
sion line to the generator site. The primary regulator
may or may not be furnished and adjusted by the
supplier. It is the responsibility of the supplier to
ensure that adequate gas pressure is available to
operate the primary regulator.
Where the primary regulator is furnished and is to be
maintained by the gas supplier, the supplier may
adjust the primary regulator outlet pressure. In any
event, a gas service technician should accomplish
adjustment of the primary regulator pressure.
Gaseous fuel pressures are usually measured with a
water manometer or with a pressure gauge that reads
“ounces per square inch”.
RESULTS:
If fuel supply and pressure are adequate, but engine
will not start, go to Test 12.
TEST 12 - CHECK WIRE 14 OUTPUT TO
DISTRIBUTOR
DISCUSSION:
When the engine is cranked either automatically or
manually, a crank relay and a run relay on the control
board are energized simultaneously. See Figure 9.
When the engine is cranking, battery voltage is deliv-
ered to the positive (+) terminal of the distributor via
Wire 14.
On startup, the crank relay de-energizes while the run
relay remains energized. Battery voltage is delivered
to the distributor via Wire 14.
PROCEDURE:
1. On the
distributor
, locate the terminal to which Wire 14
attaches.
2. Connect the positive (+) test lead of a DC voltmeter (or
VOM) to the Wire 14 terminal. Connect the other test
lead to a clean frame ground.
3. Set the AUTO-OFF-MANUAL switch to MANUAL. The
engine should crank and the meter should indicate bat-
tery voltage.
4. On startup and when the crank relay de-energizes, the
meter voltage reading should remain about the same as
when cranking.
Figure 9. Typical Prepackaged Ignition Circuit
RESULTS:
1. If meter indicates battery voltage while cranking, it may
be assumed that Wire 14 output to the
distributor
is nor-
mal. Go to Test 13.
4 5 6
11 12
CONTROL
PANEL
12-VOLT
BATTERY
13 9
11
12
14
RED
+
5
8
6
4
3
0
56
RED
0
56
BLACK
- -
16
0
14
CONTROL
STARTER
MOTOR
GROUND
GROUND
DISTRIBUTOR
NATURAL GA S
PRIMARY
REGULATOR
5-14 INCHE S WATER COLUMN OPTIMUM
GENERATOR
DEMAND
REGULATOR
MANUAL S HUTOFF VALVE
GENERATOR BA S E
GA S CARBURETOR
APPROVED FLEX LINE
(CAUTION! — KEEP FLEX FUEL LINE
S TRAIGHT)
Figure 8. Typical Natural Gas Fuel System