Guardian 4721, Repair Manual

Page: 93 / 115

DC CONTROL
LIQUID COOLED
ENGINE UNITS
SECTION 4.4
DIAGNOSTIC TESTS
PART 4
Page 89
RESULTS:
1. Replace distributor cap and rotor, if defective.
2. If inspection reveals the cap and rotor are good, go on to
Test 15.
TEST 15 - CHECK SPARK PLUGS
DISCUSSION:
This test is a continuation of the tests on the engine
ignition system.
PROCEDURE:
1. Disconnect spark plug wires by grasping the boot. Do
NOT pull on the wires.
2. Use a spark plug wrench to remove the spark plugs.
3. Spark plugs may be cleaned in a sandblast cleaner.
4. Inspect the plug insulators for cracks and chipping.
Inspect the gaskets for damage, deterioration. Check
electrodes for wear, burring, or pitting. Check spark plug
gap and set to 0.031-0.035 inch.
5. Replace spark plugs, if bad.
6. Install spark plugs and tighten to 14-22 foot-pounds of
torque (20-29 N-m).
Figure 13. Checking Spark Plug Gap
NOTE: Use Champion RN11YC4 replacement
spark plugs.
RESULTS:
1. Replace bad spark plugs.
2. If spark plugs are good, go to Test 19.
TEST 16 - CHECK IGNITION WIRES
DISCUSSION:
This is a continuation of tests on the engine ignition
system.
PROCEDURE:
Check high tension ignition wires for damage, cracks,
burned terminals, proper fit. Measure the resistance
of each wire. Shake each wire as the resistance
reading is taken. Resistance should be less than
30,000 ohms.
RESULTS:
1. Replace any defective ignition wire.
2. If wires test good, go on to Test 20.
TEST 17 - CHECK IGNITION TIMING
DISCUSSION:
If engine starts hard and runs rough, or if ft does not
start, ft may be out of time. If badly out of time, back-
firing may result.
PROCEDURE:
1. Loosen distributor hold down bolt.
2. Run engine and rotate distributor for maximum rpm.
3. Retighten distributor hold down bolt.
Figure 14. Distributor Hold Down Bolt
DISTRIBUTOR
HOLD DOWN BOLT
ADVANCE
RETARD
SET PLUG GAP AT 0.031 - 0.035 inch