TRUCK SERVICE MANUAL
FUEL SYSTEM
Capscrews And Washers
Filter Screen Optional Replacements
Capscrews used in connecting a part to aluminum
Two new fuel filter screens, both with a 40 micron mesh
should have an engaging thread length two times the
rating, are available for use in the PT fuel pumps. Filter
diameter. Observance of this rule will prevent stripping
screen, Part No. 200004, is used to replace screen, Part
threads with a capscrew that is too short or breaking a
No. 146483, when additional protection is desired in
part from using a capscrew that is too long.
single screen type fuel pumps.
Lockwashers must never be used next to aluminum.
Use of the new screen also provides a good check on
Always use a flat washer between the lockwasher and
the primary fuel filter to see If the filter is performing its
aluminum part.
proper filtration functions. Tests with a good primary
filter indicated the 200004 Screen should be cleaned at
FUEL PUMP FILTER SCREEN
50,000 mile or 1600 hour intervals. However, when a
Cummins engines are equipped with single or double
questionable primary filter was used, the screen cleaning
fuel screens, located in fuel pump housing.
periods had to be moved up to much closer intervals to
prevent clogging.
Disassembly And Inspection
Two types of screens are used on PT Fuel Pumps.
FUEL PUMP HOUSING
1. The standard automotive screen assembly mounts in
The fuel pump housing is the largest part of the fuel
top of fuel pump housing. Fig. 5-16.
pump and contains the governor barrel, throttle shaft
a. Remove upper retainer, the top retainer contains a
The drive shaft bushing, throttle sleeve, governor barrel
magnet to pick up any iron particles that may have
and spring pack housing still remain in the fuel pump
entered the fuel pump. Some screens are one piece.
main housing.
b. The lower retainer and screen has hole In center to
permit fuel flow.
The drive shaft bushing and governor barrel can be
c. Clean retainer in fuel oil and blow dry with
removed if damaged. The throttle sleeve was honed to
compressed air. Visually inspect retainer and magnet for
size after assembly to the housing, and due to the close
damage or excessive wear.
tolerances must be returned to a Cummins Distributor for
d. Proper cleaning of the filter screens can best be
repair or replacement. Exchange housings are available
accomplished by soaking In a carbon-dissolving agent,
to reduce downtime to a minimum, as this is a
followed by flushing in a sonic cleaner unit, or clean the
specialized repair and only performed by Factory Repair
screen and retainer portion in fuel oil and dry with
Stations.
compressed air.
e. Visually Inspect screen for holes or imbedded metal
Drive Shaft Bushing
particles in mesh.
f. Discard damaged or worn parts and replace with
1. Check drive shaft bushing for sign of seizure or
new parts.
burrs.
2. Check drive shaft bushing 1.D. with inside
micrometers; If worn beyond 0.7525 Inch [19.11 mm]
replace bushing.
3. Remove worn bushing using a gouge chisel or half
Inch pipe tap, After tapping bushing, screw a half inch
pipe cap on a close nipple and screw the half inch nipple
into the bushing. Insert a punch through the rear of the
housing and drive out the bushing.
4. Apply a thin coat of high pressure lubricant to a new
front drive shaft bushing; press bushing into housing
flush with housing bore using an arbor press.
Fig. 5-16, F5183. Fuel filter screens
5. Line ream bushing to 0.7495 to 0.7505 inch [19.04 to
19.06 mm] with ST-490 Ream Fixture, and a well oiled
0.750 inch (3/4 inch [19.05 mm] ) reamer, Fig. 5-17.
Check bushing I.D.
499
