Fuel Tank; Fuel Injectors - Jeep cherokee 2000 Service Manual

14 - 4 FUEL SYSTEM
DESCRIPTION AND OPERATION (Continued)
Fig. 3 Fuel Filter/Fuel Pressure Regulator
1 – FUEL FILTER/FUEL PRESSURE REGULATOR
2 – TO FUEL INJECTORS
3 – FUEL SUPPLY TUBE
4 – O-RINGS
5 – FUEL INLET FROM PUMP
6 – FUEL RETURN TO TANK
Operation for more information. Also refer to
the Fuel Pressure Leak Down Test and the Fuel
Pump Pressure Tests.
If fuel pressure at the pressure regulator exceeds
approximately 49 psi, an internal diaphragm closes
and excess fuel is routed back into the tank through
the pressure regulator. A separate fuel return line is
not used.

FUEL TANK

DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for place-
ment of the fuel pump module.
OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.
A rollover valve(s) is mounted into the top of the
fuel tank (or pump module). Refer to Emission Con-
trol System for rollover valve information.
An evaporation control system is connected to the
rollover valve(s) to reduce emissions of fuel vapors
into the atmosphere. When fuel evaporates from the
fuel tank, vapors pass through vent hoses or tubes to
a charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP). Refer to Emission Control
System for additional information.

FUEL INJECTORS

DESCRIPTION
An individual fuel injector (Fig. 4) is used for each
individual cylinder.
Fig. 4 Fuel Injector—Typical
1 – FUEL INJECTOR
2 – NOZZLE
3 – TOP (FUEL ENTRY)
OPERATION
The top (fuel entry) end of the injector (Fig. 4) is
attached into an opening on the fuel rail.
The fuel injectors are electrical solenoids. The
injector contains a pintle that closes off an orifice at
the nozzle end. When electric current is supplied to
the injector, the armature and needle move a short
distance against a spring, allowing fuel to flow out
the orifice. Because the fuel is under high pressure, a
fine spray is developed in the shape of a pencil
stream. The spraying action atomizes the fuel, add-
ing it to the air entering the combustion chamber.
The nozzle (outlet) ends of the injectors are posi-
tioned into openings in the intake manifold just
above the intake valve ports of the cylinder head.
The engine wiring harness connector for each fuel
injector is equipped with an attached numerical tag
(INJ 1, INJ 2 etc.). This is used to identify each fuel
injector.
The injectors are energized individually in a
sequential order by the powertrain control module
(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust
XJ