Guardian 4389 Repair Manual page 108

SECTION 4.4
DIAGNOSTIC TESTS
3. Set the AUTO-OFF-MANUAL switch to OFF. Reconnect
Wire 56 to starter contactor relay or starter contactor.
RESULTS:
1. If solenoid actuates, go to Test 55.
2. Replace the solenoid if it does not actuate.
TEST 55 - CHECK FOR IGNITION SPARK
DISCUSSION:
If the engine cranks but will not start, perhaps an igni-
tion system failure has occurred. A special "spark
tester" (Generac P/N 0C5969) can be used to check
for ignition spark.
Figure 19. Spark Tester
PROCEDURE:
1. Remove spark plug leads from the spark plugs
(Figure 20).
2. Attach the clamp of the spark tester to the engine cylin-
der head.
Figure 20. Checking Ignition Spark
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PART 4
3. Attach the spark plug lead to the spark tester terminal.
4. Crank the engine while observing the spark tester. If
spark jumps the tester gap, you may assume the engine
ignition system is operating satisfactorily.
NOTE: The engine flywheel must rotate at 350
rpm (or higher) to obtain a good test of the solid
state ignition system.
To determine if an engine miss is ignition related,
connect the spark tester in series with the spark plug
wire and the spark plug (Figure 21). Then, crank and
start the engine. A spark miss will be readily appar-
ent. If spark jumps the spark tester gap regularly but
the engine miss continues, the problem is in the spark
plug or in the fuel system.
NOTE: A sheared flywheel key may change igni-
tion timing but sparking will still occur across the
spark tester gap.
Figure 21. Checking Engine Miss
RESULTS:
1. If no spark or very weak spark occurs, go to Test 58.
2. If sparking occurs but engine still won't start, go to
Test 56.
3. When checking for engine miss, if sparking occurs at reg-
ular intervals but engine miss continues, go to Test 16.
4. When checking for engine miss, if a spark miss is readily
apparent, go to Test 59.
TEST 56 - CHECK SPARK PLUGS
DISCUSSION:
If the engine will not start and Test 55 indicated good
ignition spark, perhaps the spark plug(s) are fouled or
otherwise damaged. Engine miss may also be
caused by defective spark plug(s).
PROCEDURE:
1. Remove spark plugs and clean with a penknife or use a
wire brush and solvent.
DC CONTROL