SMOKE
Smoke can be quite useful as an aid in locating some
types of trouble, especially if used in conjunction with
other trouble symptoms.
The color of exhaust smoke, a good indication of
engine performance, can also be used as a guide in
troubleshooting. The exhaust of an efficiently operating
engine has little or no color. A dark, smoky exhaust
indicates incomplete combustion; the darker the color,
the greater the amount of unburned fuel in the exhaust.
Incomplete combustion may be due to a number of
troubles. Some manufacturers associate a particular
type of trouble with the color of the exhaust. The more
serious troubles are generally identified with either
black or bluish-white exhaust colors.
NOISES
INSTRUMENT INDICATIONS
CONTAMINATIOF
PRESSURE
SMOKE
TEMPERATURE
SPEED
OF LUBE OIL,
FUEL, OR WATER
Pounding
(mechanical)
Knocking
(detonation)
Clicking
(metalIic)
Rattling
Low lube oil
Low lube oil
Idling speed not
Black exhaust
Fuel oil in the
pressure
temperature
normal
smoke
lube oil
High lube oil
High lube oil
Maximum speed Bluish-white
Water in the lube
pressure
temperature
not normal
exhaust smoke
oil
Low fuel oil
Low cooling
Smoke arising
Oil or grease in
pressure (in
water tempera-
from crankcase
the water
low-pressure fuel ture (fresh)
Water in the fuel
supply system)
oil
Low cooling
High cooling
Smoke arising
Air or gas in the
water pressure
water tempera-
from cylinder
water
(fresh)
ture (fresh)
head Smoke
Metal particles
from engine
in lube oil
auxiliary equip
ment (blowers,
pumps, etc.)
Low cooling
Low cylinder ex-
water pressure
haust temperature
(salt)
High cooling
High exhaust
water pressure
temperature in
(salt)
one cylinder
Low compres-
sion pressure
Low firing
pressure
High firing
pressure
Low scavenging
air receiver pres-
sure (super-
charge engine)
High exhaust
back pressure
Figure 3-43.—Symptoms of engine troubles.
3-41
