Dodge ram truck 3500 1996 Service Manual page 1273

DESCRIPTION AND OPERATION
(Continued)
FUEL INJECTORS—8.0L ENGINE—PCM OUTPUT
The fuel injectors are attached to the fuel rail (Fig.
22). 8.0L V-10 engines use 10 Injectors.
E L E C T R I C A L MOUNTING
CONNECTOR BOLTS (6)
Fig. 22 Fuel Injectors—8.0L Engine—Typical
The nozzle ends of the injectors are positioned 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 with its
respective cylinder number.
The 10 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
injector pulse ' width based on various inputs i t
receives.
During start up, battery voltage is supplied to the
injectors through the ASD relay. When the engine is
operating, voltage is supplied by the charging sys­
tem. The PCM determines injector pulse width based
on various inputs.
FUEL PUMP RELAY-PCM OUTPUT
The PCM energizes the electric fuel pump and the
oxygen sensor (02S) heating element through the
fuel pump relay. Battery voltage is applied to the fuel
pump relay when the ignition key is ON. The relay is
energized when a ground signal is provided by the
PCM.
Refer to Automatic Shutdown Relay—PCM Output
for additional information.
The fuel pump will operate for approximately one
second unless the engine is operating or the starter
motor is engaged.
The fuel pump relay is located in the Power Distri­
bution Center (PDC) (Fig. 19).
GENERATOR FIELD—PCM OUTPUT
The powertrain control module (PCM) regulates
the charging system voltage within a range of 12.9 to
15.0 volts. Refer to Groups 8A and 8C for charging
system information.
GENERATOR LAMP—PCM OUTPUT
I f the powertrain control module (PCM) senses a
low charging condition in the charging system, i t will
illuminate the generator lamp (if equipped) on the
instrument panel. For example, during low idle with
all accessories turned on, the lamp may momentarily
go on. Once the PCM corrects idle speed to a higher
rpm, the lamp will go out. Refer to Groups 8A and
8C for charging system information.
IDLE AIR CONTROL (IAC) MOTOR—3.9L/5.2L/5.9L
ENGINES—PCM OUTPUT
The IAC motor is mounted to the back of the throt­
tle body (Fig. 15) and is controlled by the powertrain
control module (PCM).
The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage (Fig. 23) and regulates air flow
through it. Based on various sensor inputs, the pow­
ertrain control module (PCM) adjusts engine idle
speed by moving the IAC motor pintle in and out of
the air control passage. The IAC motor is positioned
when the ignition key is turned to the On position.
A (factory adjusted) set screw is used to mechani­
cally limit the position of the throttle body throttle
plate. Never attempt to adjust the engine idle
speed using this screw. All idle speed functions are
controlled by the PCM.
IDLE AIR CONTROL (IAC) MOTOR—8.0L
ENGINE—PCM OUTPUT
The IAC motor is mounted to the side of the throt­
tle body (Fig. 24) and is controlled by the powertrain
control module (PCM).
The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage (Fig. 25) * and regulates air flow
through it. Based on various sensor inputs, the pow­
ertrain control module (PCM) adjusts engine idle
speed by moving the IAC motor pintle in and out of