CONTENTS
FAULTY COMPONENTS
ACCESSORIES AND MISC.
SPARK PLUGS

DRY, SOFT, BLACK, SOOTY DEPOSITS

CONDITION(S)

• SPARK PLUG HAS DRY, SOFT, BLACK, SOOTY (CARBON) DEPOSITS

POTENTIAL CAUSE(S)

CHECK THESE FIRST:

1. RICH FUEL/AIR MIXTURE
Have fuel/air mixture professionally adjusted.
Clean and reuse plug(s).

2. STICKING CARBURETOR CHOKE
Clean carburetor choke.
Clean and reuse plug(s).

3. HIGH FUEL PRESSURE
Have fuel pump or fuel pressure regulator professionally replaced.
Clean and reuse plug(s).

4. WORN BREAKER POINTS
Have breaker points professionally replaced.
Clean and reuse plug(s).

CHECK THESE NEXT:

5. CLOGGED AIR CLEANER FILTER
Replace air cleaner filter.
Clean and reuse plug(s).

6. PROLONGED SLOW, STOP AND START DRIVING OR IDLING
Avoid low speed engine operation; alter driving habits.
Clean and reuse plug(s).

7. RETARDED IGNITION TIMING
Have ignition timing professionally advanced.
Clean and reuse plug(s).

8. LEAKING VALVES (LOWER COMPRESSION)
Have valves professionally repaired.
Clean and reuse plug(s).

CHECK THESE LAST:

9. CORRODED OR CRACKED SPARK PLUG WIRE(S)
Replace spark plug wire(s).
Clean and reuse plug(s).

10. CRACKED DISTRIBUTOR CAP
Replace distributor cap.
Clean and reuse plug(s).

11. SPARK PLUG HEAT RANGE TOO COLD
Install new spark plug(s) with higher heat range.

12. DEFECTIVE HEAT RISER VALVE
Have heat riser valve professionally repaired.
Clean and reuse plug(s).

IN EVERY CASE, CLEAN AND REUSE YOUR SPARK PLUGS.

CONTENTS
CLEAN, WHITE, OFTEN-BLISTERED INSULATOR
LIGHT TAN, GRAYISH-WHITE, OR RUSTY COLORED DEPOSITS