6 Y -4 8 ENGINE ELECTRICAL
Brown to grayish-tan deposits and slight electrode wear indicate correct spark
plug heat range and mixed periods of high and low speed driving.
SPARK PLUGS
HAVING THIS APPEARANCE MAY BE CLEANED, REGAPPED AND REIN
STALLED.
When reinstalling spark plugs that have been cleaned and regapped, be sure to use
new gaskets on spark plugs that utilize engine seat gaskets.
NORMAL OPERATION
Normal Operation
Deposit Fouling " A ”
Deposit Fouling " B ”
DEPOSIT FOULING—"A ”
Red, brown, yellow and white colored coatings which accumulate on the insula
tor are by-products of combustion and come from the fuel and lubricating oil, both
of which today generally contain additives. Most powdery deposits have no 'adverse
effect on spark plug operation; however, they may cause intermittent missing under
severe operating conditions, especially at high speeds and heavy load.
IF THE INSULATOR IS NOT TOO HEAVILY COATED, THE SPARK PLUGS
MAY BE CLEANED, REGAPPED AND REINSTALLED.
Sometimes, even after cleaning, an invisible shunt path remains. The only remedy
under such circumstances is to replace the plug.
DEPOSIT FOULING—"B"
Most powdery deposits, as shown in “A”, have no adverse effect on the operation
of the spark plug as long as they remain in the powdery state. However, under certain
conditions of operation, these deposits melt and form a shiny yellow glaze coating on
the insulator which, when hot, acts as a good electrical conductor. This allows the
current to follow the deposits instead of jumping the gap, thus shorting out the spark
plug.
Glazed deposits can be avoided by not applying sudden load, such as wide open
throttle acceleration, after sustained periods of low speed and idle operation.
IT IS
ALMOST IMPOSSIBLE TO EFFECTIVELY REMOVE GLAZED DEPOSITS, SO
WHEN THEY OCCUR THE PLUG SHOULD BE REPLACED.
CARBON FOULING
Dry, fluffy black carbon deposits may result from overrich carburetion, excessive
hand choking, a faulty automatic choke, or a sticking manifold heat valve. A clogged
air cleaner can restrict air flow to the carburetor causing rich mixtures. Poor ignition
output (faulty breaker points, weak coil or condenser, worn ignition cables) can
reduce voltage and cause misfiring. Fouled spark plugs are the result-not the
cause-of this problem.
AFTER THE CAUSE HAS BEEN ELIMINATED, SPARK
PLUGS HAVING THIS APPEARANCE CAN BE CLEANED, REGAPPED AND
REINSTALLED.
Excessive idling, slow speeds under light load also can keep spark plug tempera
tures so low that normal combustion deposits are not burned off. In such a case a
hotter type spark plug will better resist carbon deposits.
Carbon Fouling
LIGHT DUTY TRUCK SERVICE MANUAL
Summary of Contents for Light Duty Truck 1973
Page 1: ......
Page 4: ......
Page 6: ......
Page 53: ...HEATER AND AIR CONDITIONING 1A 27 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 115: ...LIGHT DUTY TRUCK SERVICE M A N U A L HEATER AND AIR CONDITIONING 1A 89...
Page 123: ...BODY 1B 3 Fig 6 Typical 06 Van LIGHT DUTY TRUCK SERVICE MANUAL...
Page 149: ...BODY 1B 29 Fig 84 Body Mounting 06 Fig 85 Body Mounting 14 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 171: ...LIGHT DUTY TRUCK SERVICE M A N U A L Fig 2 Frame Horizontal Checking Typical FRAME 2 3...
Page 173: ...LIGHT DUTY TRUCK SERVICE M A N U A L Fig 4 10 30 Series Truck Frame FRAME 2 5...
Page 174: ...2 6 FRAME LIGHT DUTY TRUCK SERVICE MANUAL Fig 5 Underbody Reference Points G Van...
Page 185: ...FRONT SUSPENSION 3 11 Fig 16 Toe out on Turns LIGHT DUTY TRUCK SERVICE MANUAL...
Page 224: ......
Page 266: ......
Page 351: ...ENGINE 6 15 Fig ID Sectional View of Eight Cylinder Engine LIGHT DUTY TRUCK SERVICE MANUAL...
Page 375: ...EN G IN E 6 39 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 376: ...6 4 0 ENGINE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 377: ...ENG IN E 6 41 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 378: ...LIGHT DUTY TRUCK SERVICE MANUAL Fig 37L K Series Engine Front Mount 6 42 ENG INE...
Page 400: ...6 6 4 ENG INE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 401: ...ENG IN E 6 65 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 402: ...6 6 6 ENGINE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 403: ...E NG IN E 6 67 Fig 36V C Series Engine Mounts LIGHT DUTY TRUCK SERVICE MANUAL...
Page 410: ......
Page 423: ...EN G IN E C OOLING 6K 13 Fig 16 Overheating Chart LIGHT DUTY TRUCK SERVICE MANUAL...
Page 424: ...6 K 1 4 ENG INE COOLING Fig 17 Coolant Loss Chart LIGHT DUTY TRUCK SERVICE MANUAL...
Page 456: ...6M 32 ENGINE FUEL Fig K15 Accelerator Controls G Van L 6 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 492: ......
Page 512: ...Fig 18e Vacuum Advance Diagram V8 Engine...
Page 516: ...6 T 2 4 E M IS S IO N CONTROL SYSTEMS LIGHT DUTY TRUCK SERVICE MANUAL...
Page 528: ......
Page 590: ......
Page 593: ...CLUTCHES MANUAL TRANSMISSIONS 7M 3 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 598: ...7M 8 CLUTCHES MANUAL TRANSMISSIONS LIGHT DUTY TRUCK SERVICE MANUAL...
Page 642: ......
Page 654: ......
Page 743: ...FUEL TANKS AND EXHAUST 8 13 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 744: ...8 14 FUEL TANKS AND EXHAUST LIGHT DUTY TRUCK SERVICE MANUAL...
Page 760: ...8 30 FUEL TANKS AND EXHAUST Fig 40 Exhaust Pipe P Models LIGHT DUTY TRUCK SERVICE MANUAL...
Page 761: ...FUEL TANKS AND EXHAUST 8 31 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 763: ...FUEL TANKS AND EXHAUST 8 33 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 766: ......
Page 832: ...LIGHT DUTY TRUCK SERVICE MANUAL Fig 106 Power Steering Pump Mounting Typical 9 66 STEERING...
Page 833: ...PUMP ASSEMBLY STEERING GEAR TYPICAL SMALL V8 TYPICAL LARGE V8 STEERING 9 67...
Page 861: ...STEERING 9 95 Fig 134 Power Steering Pump Leakage LIGHT DUTY TRUCK SERVICE MANUAL...
Page 864: ......
Page 876: ......
Page 886: ...11 10 CHASSIS SHEET METAL LIGHT DUTY TRUCK SERVICE MANUAL...
Page 891: ...ELECTRICAL BODY AND CHASSIS 12 5 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 934: ......
Page 942: ......
Page 970: ......
Page 972: ......
Page 974: ......
Page 976: ...V...
Page 978: ......
Page 979: ......