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Figure 29. Checking Engine Miss
RESULTS:
1. If no spark or very weak spark occurs, go to Test 73.
2. If sparking occurs but engine still won’t start, go to Test 71.
3. When checking for engine miss, if sparking occurs at
regular intervals but engine miss continues, go to Test 20.
4. When checking for engine miss, if a spark miss is readily
apparent, go to Test 74.
TEST 71 – CHECK SPARK PLUGS
DISCUSSION:
If the engine will not start and Test 70 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.
2. Replace any spark plug having burned electrodes or
cracked porcelain.
3. Set gap on new or used spark plugs as follows:
Engine Size
kW
Rating
Plug Gap
Recommended
Plug
410 cc 8 kW 0.030 inch RC14YC
530 cc 10 kW 0.030 inch BPR6HS
990 cc 10-17 kW 0.040 inch RC14YC
999 cc 20 kW 0.030 inch RC12YC
RESULTS:
1. Clean, re-gap or replace spark plugs as necessary.
2. If spark plugs are good, refer back to flow chart.
NORMAL MISFIRES
PRE-IGNITION DETONATION
Figure 30. Spark Plug Conditions
Figure 31. Checking Spark Plug Gap
TEST 72 – CHECK ENGINE / CYLINDER LEAK
DOWN TEST / COMPRESSION TEST
GENERAL:
Most engine problems may be classified as one or a
combination of the following:
• Willnotstart
• Startshard
• Lackofpower
• Runsrough
• Vibration
• Overheating
• Highoilconsumption
PART 4
DC CONTROL
SECTION 4.4
DIAGNOSTIC TESTS