6E1–311
X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
D
The camshaft position (CMP) sensor.
D
The idle air control (IAC) valve.
D
The fuel pump.
D
The fuel pump relay.
Basic System Operation
The fuel metering system starts with the fuel in the fuel
tank. An electric fuel pump, located in the fuel tank,
pumps fuel to the fuel rail through an in–line fuel filter. The
pump is designed to provide fuel at a pressure above the
pressure needed by the injectors. A fuel pressure
regulator in the fuel rail keeps fuel available to the fuel
injectors at a constant pressure. A return line delivers
unused fuel back to the fuel tank. Refer to Section 6C for
further information on the fuel tank, line filter, and fuel
pipes.
Fuel Metering System Purpose
The basic function of the air/fuel metering system is to
control the air/fuel delivery to the engine. Fuel is delivered
to the engine by individual fuel injectors mounted in the
intake manifold near each intake valve.
The main control sensor is the heated oxygen sensor
(HO2S) located in the exhaust system. The HO2S tells
the ECM how much oxygen is in the exhaust gas. The
ECM changes the air/fuel ratio to the engine by controlling
the amount of time that the fuel injector is ON. The best
mixture to minimize exhaust emissions is 14.7 parts of air
to 1 part of gasoline by weight, which allows the catalytic
converter to operate most efficiently. Because of the
constant measuring and adjusting of the air/fuel ratio, the
fuel injection system is called a ”Closed Loop” system.
The ECM monitors signals from several sensors in order
to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called ”modes.”
All modes are controlled by the ECM.
Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm–operated
relief valve mounted on the fuel rail with fuel pump
pressure on one side and manifold pressure on the other
side. The fuel pressure regulator maintains the fuel
pressure available to the injector at three times
barometric pressure adjusted for engine load. It may be
serviced separately.
If the pressure is too low, poor performance and a DTC
P0171, or DTC P1171 will be the result. If the pressure is
too high, a DTC P0172 will be the result. For information
on diagnosing fuel pressure conditions, refer to Fuel
System Diagnosis.
014RX038
Fuel Pump Electrical Circuit
When the key is first turned ON, the ECM energizes the
fuel pump relay for two seconds to build-up the fuel
pressure quickly. If the engine is not started within two
seconds, the ECM shuts the fuel pump off and waits until
the engine is cranked. When the engine is cranked and
the 58X crankshaft position signal has been detected by
the ECM, the ECM supplies 12 volts to the fuel pump relay
to energize the electric in–tank fuel pump.
An inoperative fuel pump will cause a ”no–start” condition.
A fuel pump which does not provide enough pressure will
result in poor performance.
Fuel Rail
The fuel rail is mounted to the top of the engine and
distributes fuel to the individual injectors. Fuel is delivered
to the fuel inlet tube of the fuel rail by the fuel lines. The
fuel goes through the fuel rail to the fuel pressure
regulator. The fuel pressure regulator maintains a
constant fuel pressure at the injectors. Remaining fuel is
then returned to the fuel tank.
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