Chevrolet 70 Series 1970, Service Manual

Page: 391 / 841

TROUBLE DIAGNOSIS CHART
GASOLINE ENGINES 6A-20
HARD STARTING
SYMPTOM A - SLOW CRANKING
POSSIBLE CAUSES REMEDY
1. Heavy engine oil.
1. Change to ligh ter o il.
2. Partially d ischarged battery. 2. Charge battery.
3. Faulty or undercapacity battery. 3. R eplace battery.
4. Poor battery connections.
4. Clean and tighten or rep lace connections.
5. Faulty sta rter solenoid.
5. Replace or repair solenoid.
6. Faulty starting m otor or d rive. 6. Overhaul starting motor.
SYMPTOM B - LOW CYLINDER COMPRESSION
POSSIBLE CAUSES
REMEDY
1. Burned or warped v a lv e s.
1. Overhaul cylinder head.
2. Improper valve la sh . 2. Adjust to proper clearan ce.
3. Worn or broken piston rin gs. 3. Overhaul engine.
4. D efective cylin d er head gasket. 4. R eplace gasket.
SYMPTOM C - LACK OF FUEL
POSSIBLE CAUSES REMEDY
1. Fuel lin e s clogged. 1. Clean fuel lin es.
2. Low fuel supply. 2. Check amount of fuel in tank, fill if supply is low.
3. Clogged vent in fuel tank cap. 3. Clean or rep lace cap.
4. Break in fuel supply line allowing air to be
drawn into fuel lin e. 4. R eplace or repair lin e s.
5. Clogged fuel filte r . 5. S ervice filte r a s recom m ended in applicable
portion of ENGINE FUEL SYSTEM (SEC. 6M).
6. Water or ic e in fuel sy stem .
6. Thaw if frozen, and drain water out of tank and
filte r s .
7. D efective fuel pump.
7. Make p re ssu r e te st at pump outlet.
8. D irty carburetor.
8. Clean carburetor.
9. Carburetor choke inoperative, or not properly
adjusted.
9. Check choke operation and adjust as n e c e ssa r y .
SYMPTOM D - IGNITION TROUBLES
POSSIBLE CAUSES REMEDY
1. D istributor points burned or corroded. 1. Clean or rep lace points.
2. D istributor points out of adjustment.
2. Adjust point gap.
3. Faulty spark plugs. 3. Clean or rep lace and adjust spark plug gap.
4. D efective w iring. 4. Inspect w iring and co r r e ct as required.
5. Ignition out of tim e. 5. Set ignition tim ing.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCKSHOP MANUAL