Check Spark Plug; Check Ignition Coil - Guardian 4700 Repair Manual

Section 7
DIAGNOSTIC TESTS
SPARK TESTER CLAMP
CONNECTED TO
SPARK TESTER
SPARK PLUG
Figure 7-24. – Checking Engine Miss
RESULTS:
1. If no spark or if engine miss is apparent, go to Test 34.
2. If ignition spark is good, go to Test 33.
TEST 33 - CHECK SPARK PLUG
DISCUSSION:
During Test 32, if spark jumped the tester gap, the
ignition system must be functioning properly.
However, if the engine misses the spark plug itself
may be fouled.
PROCEDURE:
Remove spark plug. Clean with a commercial solvent.
DO NOT BLAST CLEAN SPARK PLUGS. Replace
spark plug if badly fouled, if ceramic is cracked, or if
badly worn or damaged. Set gap to 0.030 inch
(0.76mm). Use a Champion RC12YC (or equivalent)
replacement spark plug.
SET PLUG GAP AT 0.030 inch
(0.76 mm)
Figure 7-25. – Setting Spark Plug Gap
Page 46
RESULTS:
1. Clean and regap or replace spark plug as necessary.
2. If spark plug is good, go to Test 36.
SPARK PLUG
BOOT
DISCUSSION:
The ignition system used on GH-220 engines is a
solid-state (breakerless) type. The system utilizes a
magnet on the engine flywheel to induce a relatively
low voltage into an ignition coil assembly. Ignition coil
internal components increase the voltage and deliver
the resulting high voltage across the spark plug gap.
The ignition coil houses a solid state-circuit board that
controls ignition timing. Timing is fixed, air gap is non-
adjustable and spark advance is automatic.
Major components of the ignition system include (a)
the ignition coil assembly, (b) the spark plug, (c) the
engine control board and (d) the engine flywheel.
Solid-state components encapsulated in the ignition
coil are not accessible and cannot be serviced. If the
coil is defective, the entire assembly must be
replaced. The air gap between the coil and the fly-
wheel magnet is fixed and non-adjustable.
The ignition coil assembly (Figure 7-26) consists of
(a) ignition coil, (b) spark plug high tension lead and
(c) spark plug boot.
PROCEDURE:
1. Disconnect Wire No. 18A at the Bullet Connector. Repeat Test
32.
2. If unit now produces spark, disconnect J1 Connector from ECB
(Engine Control Board). Set the VOM to measure resistance.
Connect one test lead to Wire No. 18A (Pin Location J1-4).
Connect the other test lead to a clean frame ground. Infinity
should be measured.
3. If Step 1 produced spark and Step 2 tested good, set the VOM
to measure DC voltage. Connect one test lead to Wire No. 15
(J3 Terminal) on ECB. Connect the other test lead to frame
TEST 34 - CHECK IGNITION COIL
SPARK PLUG
HIGH TENSION
LEAD
Figure 7-26 – Ignition Coil Assembly
SPARK
PLUG
BOOT
IGNITION COIL