Battery Voltage Correction Mode; Fuel Cutoff Mode; F U E L C O N T R O L S Y S T E M C O M P O N E N T S C2-3; Basic System Operation - Pontiac Fiero 1988 Service Manual

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT) 6E3-C2-3
Deceleration Mode
When deceleration occurs, the fuel remaining in
the intake port can cause excessive emissions and
backfiring. Again, the electronic control module
(ECM) looks at changes in throttle position and
manifold pressure, and reduces the amount of fuel.
When deceleration is very fast, the ECM can cut
"OFF" fuel completely for short periods.
Battery Voltage Correction Mode
When battery voltage is low, the ECM can
compensate for the weak spark delivered by the
distributor by:
• Increasing the amount of fuel delivered
• Increasing the idle rpm
• Increasing ignition dwell time.
Fuel Cutoff Mode
No fuel is delivered by the injectors when the
ignition is "OFF." This prevents dieseling. Also, fuel
is not delivered if no reference pulses are seen from
the distributor, which means the engine is not
running. This prevents flooding.
FUEL CONTROL SYSTEM
COMPONENTS
The Fuel control system is made up of the
following parts:
1) Fuel rail assembly, including:
• Fuel injectors
• Pressure regulator
Throttle body assembly, including:
• Idle air control (IAC) valve
• Throttle position sensor (TPS)
Fuel pump
Fuel pump relay.
2)
3)
4)
BASIC SYSTEM OPERATION
The fuel control system (Figure C2-4) starts with
the fuel in the fuel tank. An electric fuel pump,
located in the fuel tank with the gage sending unit,
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
pressure regulator in the fuel rail keeps fuel available
to the injectors at a constant pressure. Unused fuel is
returned to the fuel tank by a separate line. (For
further information on the fuel tank, in-line filter, and
fuel lines, see Section "6C").
The injectors are controlled by the ECM. They
deliver fuel in one of several modes, as described
above.
Figure C2-4 - Fuel Supply System (Typical)
PH FUEL RAIL A S S E M B L Y
FUEL BLOCK
FUEL PRESSURE CONNECTION
PH F U E L I N J E C T O R
PH C O L D START FITTING
B P R E S S U R E R E G U L A T O R A S S E M B L Y
8
P 0944-AS
Figure C2-5 Model R610(F6A) Fuel Rail Assembly
In order to properly control the fuel supply, the
fuel pump is operated by the ECM thru the fuel pump
relay and oil pressure switch (see "Fuel Pump
Electrical Circuit," below).