TM-5-3805-254-14-P-2
TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)
TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)
JUNE 1980
TM-5-3805-254-14-P-2 - Page 462 of 894
FUEL SYSTEM
TRUCK SERVICE MANUAL
Operating Principles
The PT fuel system is used exclusively on Cummins
Diesels. The identifying letters, “PT,” are an abbreviation
for “pressure time.”
Injector Description
The PT Injector is a simple mechanical unit which
receives fuel from the fuel pump under pressure and
meters, injects and atomizes it through fine injector cup
spray holes into the combustion chamber.
The general description “PT Injectors” is used only to
indicate that the injector is used with the PT fuel system
and not with the former Cummins Disc fuel system.
Cylindrical PT (type D) Injectors
The PT (type D) Injector is a refinement of the PT (type B
and C) cylindrical injectors used in Cummins engines
with internal fuel drillings.
The PT (type D) top stop
injector is shown in Fig.
6-1-5.
By parts design changes, the PT (type D) provides more
parts interchangeability and those areas subject to wear
are localized in smaller parts for easier servicing.
Former injectors have a body with the moving part or
plunger running the full length, the PT (type D) has a
short barrel and plunger to provide the same function.
The shorter barrel plunger bore made possible use of
materials with greater wear resistance and results in
smaller replacement assembly.
The barrel/plunger
assembly is made up of a coupling (3, Fig.
6-1-5),
plunger (11) and barrel (12); the coupling and plunger
are swaged assembly.
The “Top-Stop” injector functions like the standard PT
(type D) injector except the upward travel of the injector
plunger is limited by an adjustable stop.
The stop is set
before the injector is installed in the engine.
Fig.
6-1-5.
Injector Parts-PT (type D)
Adapter
In Fig.
6-1-5, the adapter (2) houses the plunger return
spring (1), adjustable orifice (5), orifice gasket (4), fuel
screen (6) and screen retainer (7) and carries the “O”
ring seals (8) on the outside which seal against the head
to form fuel inlet and drain passages.
Fuel enters
through orifice (5) and flows to barrel (12), pass check
ball (10) to the cup-to-barrel passage up to the metering
orifice where it is metered into the cup (14).
Fuel not
used circulates past the metering orifice, around the
plunger and out the drain passage while the plunger is
seated in the cup.
The cup, adapter and barrel are held
in assembled position by the cup retainer (13).
Metering Orifice of PT (type D) Injector
The metering orifice near the cup end of the barrel is of
fixed size and must not be altered In any way, barrels
differ for engine model In relation to the size of the
metering orifice as governed by engine fuel requirements
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