GMC 1976 ZEO 6083 Maintenance Manual page 282

GENERAL
Oil too heavy (viscosity) .
Main oil passage on pressure side of pump
clogged.
GENERAL
Faulty oil gauge sending unit .
Leakage at internal oil passage.
Low oil level in oil pan.
GENERAL
Suction loss .
Oil pressure gauge faulty .
Not enough oil in pan.
Pipe to oil pressure gauge stopped up .
Oil passage on discharge side of pump
stopped up .
Oil screen or passages on intake side of
pump stopped up .
GENERAL
Over-speeding engine .
Deposits on valve seats and/or gum
formation on stems or guides .
Warped valves or faulty valve forgings .
Exhaust back pressure .
Improper ignition timing .
HIGH OIL PRESSURE
NO OIL PRESSURE
MECHANICAL
Faulty gauge.
Oil pressure relief valve adjustment too
heavy.
Relief valve spring too stiff.
Oil pressure passage clogged .
NO OIL PRESSURE WHILE IDLING
MECHANICAL
Oil pump not functioning properly . (Valve
stuck by foreign material .)
Excessive clearance at bearings (camshaft,
rod or main).
NO OIL PRESSURE WHILE ACCELERATING
GENERAL MECHANICAL
Leakage at internal oil passages .
MECHANICAL
Oil pump inoperative.
Relief valve stuck open .
BURNED, STICKING OR BROKEN VALVES
MECHANICAL
ENGINE
6A- 1 7
Weak valve springs.
Improper valve clearance.
Improper valve guide clearance
worn valve guides .
Out-of-round valve seats or incorrect
valve seat width.
and/or