Chevrolet 70 Series 1970, Service Manual

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53 AND 71 SERIES DIESEL ENGINES 6C-58
EXHAUST SMOKE ANALYSIS
(Checks to be made with water outlet temperature of 160°F. minimum)
BLACK OR GRAY SMOKE
INCOMPLETELY BURNED FUEL—Check for the following:
1. Insufficient Combustion Air—High exhaust back pressure (measured with manometer) —
Check exhaust piping and muffler for obstruction.
2. Restricted Air Inlet—
a. Cylinder liner ports clogged—Clean liner ports.
b. Air cleaner clogged or damaged—Remove and clean, repair or replace damaged parts.
c. Emergency stop not completely open—Check operation of emergency shutdown device
and adjust if necessary.
d. Blower to air horn screen clogged—Remove screen and clean.
EXCESSIVE FUEL OR IRREGULAR FUEL DISTRIBUTION-Check for the following:
1. Improper Injector Rack Setting—Perform operations as directed in
( Section 6 C ).
2. Improper Timing of Injectors—Time fuel injectors as directed under “Injector Timing”
in ( Section 6 C ).
3. Faulty Injectors—Replace injectors.
4. Lugging Engine—Correct driving practices.
IMPROPER GRADE OF FUEL-Refer to Current Diesel Fuel Oil Service Bulletin.
BLUE SMOKE
FUEL OR LUBRICATING OIL NOT BURNED IN CYLINDER (BLOWN THROUGH CYL­
INDER DURING SCAVENGING PERIOD)-Check for the following:
1. Internal Lubricating Oil Leaks—Refer to “High Lubricating Oil Consumption”
2. Pullover of Air Cleaner Oil—Oil level to high or to light viscosity.
FAULTY INJECTOR-Refer to “Uneven Running or Frequent Stalling” in “Abnormal Engine
Operation”
COOLING SYSTEM TEMPERATURE BELOW NORMAL-Refer to “Abnormal Engine Coolant
Temperatures’.’
WHITE SMOKE
MIS-FIRING CYLINDERS-Check for the following:
1. Faulty Injectors—Replace injectors.
2. Low Compression—Refer to “Hard Starting’.’
3. Low Cetane Fuel—Refer to Current Diesel Fuel Oil Service Bulletin.
T-6934
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL