Chevrolet Light Duty Truck 1973 Service Manual page 406

6-70 ENGINE
EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING
a. Intake valve seals damaged or missing.
b. Worn valve stems or guides.
c. Plugged drain back holes in head.
EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING
COMBUSTION CHAMBER BY PASSING PISTON RINGS
a.
Oil level too high.
b. Excessive main or connecting rod bearing
clearance
c. Piston ring gaps not staggered.
°
d. Incorrect size rings installed.
e. Piston rings out of round, broken or scored.
°
f. Insufficient piston ring tension due to engine
overheating.
a. Faulty oil gauge sending unit.
b. Oil pump not functioning properly. (Regulator ball
stuck in position by foreign material).
a. Low oil level in oil pan.
a. Weak valve springs.
b. Improper valve lifter clearance.
c. Improper valve guide clearance and/or worn valve
guides.
d. Out-of-round valve seats or incorrect valve seat
width.
COMBUSTION CHAMBER THROUGH HEAD AREA
OD
NO OIL PRESSURE WHILE IDLING
NO OIL PRESSURE WHILE ACCELERATING
BURNED, STICKING OR BROKEN VALVES
CAUSE
d. Intake manifold gasket leak in conjunction with
rocker cover gasket leak.
CAUSE
Ring grooves or oil return slots clogged.
g.
h. Rings sticking in ring grooves of piston,
i. Ring grooves worn excessively in piston.
^ • •
J- Compression rings installed upside down.
> • ,
k. Excessively worn or scored cylinder walls.
, ~ , . .
1. Oil too thin.
CAUSE
c. Excessive clearance at main and connecting rod
bearings.
d. Loose camshaft bearings.
e. Leakage at internal oil passages.
CAUSE
b- Leakage at internal oil passages.
CAUSE
e. Deposits on valve seats and/or gum formation on
stems or guides.
Wart'ed valves or faul|y valve forSinSs-
f
Exhaust back pressure.
g.
h. Improper spark timing,
• ,, , . . .
. . .
LIGHT DUTY TRUCK SERVICE MANUAL