Specifications

12
loose drive components. If damage to the
compressor crankshaft is detected,
replace the compressor or the crankshaft.
When in stalling the drive gear or pulley,
torque the crankshaft nut to 100 foot
pounds. DO NOT BACK OFF THE
CRANKSHAFT NUT TO ALIGN THE
COTTER PIN AND CASTELLATED NUT.
(Some compressors do not use
castellated nuts.) DO NOT USE IMPACT
WRENCHES.
B. Inspect drive gear and couplings and
engine for excessive wear. Replace as
necessary. (Nonmetallic gears should be
replaced when the compressor is
changed.) 501 drive gear should be
metal-type on Detroit Diesel engine.
C. Inspect the compressor discharge port
and discharge line for carbon build-up. If
carbon is detected, check for proper
cooling to the compressor. (See Cause
and Remedy (D) under Symptom #1.)
Inspect the discharge line for kinks and
restrictions. Replace discharge line as
necessary.
D. Check for proper oil pressure in the
compressor. Minimum required oil
pressure, 5 psi engine idling, 15 psi
maximum governed engine rpm. Check
for excessive oil temperature - should not
exceed 240° F.
E. Replace or repair the compressor after
determining none of the preceding
installation defects exist.
A. Inspect engine or compressor air filter
and replace if necessary.
B. Inspect the compressor air induction line
for for kinks and restrictions and replace
as necessary.
C. Inspect the compressor discharge port
and compressor discharge cavity. line for
restrictions and carbon build-up. If a
carbon build-up is found, check for proper
compressor cooling. Replace faulty
sections of the discharge line.
D. Check for faulty drive gears and couplings
and replace as necessary. Check the
condition of drive belts and replace or
tighten, whichever is appropriate.
E. Test for excessive system leakage and
repair as necessary. Use the following as
a guide: Build system pressure to
governor cutout and allow the pressure to
stabilize for one minute. Using the dash
gauge, note the system pressure and the
pressure drop after two minutes. The
pressure drop for Pre-1975 vehicles
should not exceed:
1. 4 psi for a single vehicle.
2. 6 psi for a tractor trailer.
3. 10 psi for a tractor and 2 trailers. The
pressure drop for Post-1975 vehicles should
not exceed:
1. 2 psi in each reservoir for a single vehicle.
2. 6 psi in each reservoir for a tractor and trailer.
3. 8 psi in each reservoir for a tractor and 2
trailers.
F. Check the operation of the unloading
pistons in the inlet cavity of the
compressor. Both pistons should have
the plunger flanges resting on the inlet
cavity floor when the compressor is
loaded (pumping air). If the pistons and
plunger are not fully retracted, check for
proper operation of the compressor air
governor. If the governor is operating
properly, replace the unloader pistons
SYMPTOMS CAUSE REMEDY
3. Excessive build-up and
recovery time. Compressor should
be capable of building air system
from 85-100 psi in 40 seconds
with engine at full governed rpm.
Minimum compressor
performance is certified to meet
Federal requirements by the
vehicle manufacturer. Do not
downsize the original equipment
compressor.
B. Excessively worn drive
couplings or gears.
C. Compressor cylinder head
or discharge line
restrictions.
D. Worn or burned out
bearings.
E. Faulty compressor.
A. Dirty induction air filter.
B. Restricted induction line.
C. Restricted discharge line or
compressor discharge
cavity.
D. Slipping drive components.
E. Excessive air system
leakage.
F. Sticking unloader pistons