Oil Pump Overhaul - GMC T Series 1994 Repair Manual

• Valve spring damper clicking on rotator. To
check valve spring and guide clearance,
remove the rocker covers:
a. Occasionally this noise can be eliminated
by rotating the valve spring and valve.
Crank engine until noisy valve is off its
seat. Rotate spring. This will also rotate
valve. Repeat until valve becomes quiet. If
correction is obtained, check for an off
square valve spring. If spring is off square
more than 1/16 inch in free position,
replace spring.
b. Check for excessive valve stem to guide
clearance. Correct as required.
6 Valves noisy regardless of engine speed:
.
This condition can be caused by foreign particles
or excessive valve lash.
Check for valve lash by turning engine so the
piston in that cylinder is on top dead center of
firing stroke. If valve lash is present, the pushrod
can be freely moved up and down a certain
amount with rocker arm held against valve.
Valve lash indicates one of the following:
• Worn pushrod.
• Worn rocker arm.
• Lifter plunger stuck in down posi'tion due to
dirt or carbon.
• Faulty lifter.
• Worn camshaft lobe.
Checking the above five items:
• Look at the upper end of pushrod. Excessive
wear of the spherical surface indicates one of
the following conditions:
a. Improper hardness of the pushrod ball. The
pushrod and rocker arm must be replaced.
b. Improper lubrication of the pushrod. The
pushrod and rocker arm must be replaced.
The oiling system to the pushrod should be
checked.
• Excessive camshaft lobe or lifter wear. Install
a dial indicator on pushrod side of rocker arm
with the piston at T.D.C. compression stroke
and measure the camshaft lobe lift while
turning the engine
Compare lobe
specifications.
a. If measurement obtained does not meet
specifications, the camshaft lobe and/or
lifter are worn and must be replaced.
• If pushrod appears in good condition, has been
properly lubricated, and lobe lift is within
specifications replace rocker arm and recheck
valve lash.
• If valve lash still exists, trouble is in the lifter.
Lifter should be replaced.
two full revolutions.
lift measured with the

OIL PUMP OVERHAUL

Figures 41 through 45 and 53
^►l Disassemble
1. Drain oil from pump.
2. Pump cover.
NOTICE:
Do not remove pickup tube from
cover unless loose or broken.
3. Pump gears.
CAUTION: The pressure regulator
valve spring is under pressure.
Exercise caution when removing the
retaining pin, as bodily injury may
result.
4. Pressure regulator valve.
• Plug.
• Spring.