5
NOTE:
Further instructions are available on the operation of the digital fuel injection system in the
PRO-JECTION 2D
fuel injection
installation manual.
SELECTION BETWEEN SMALL BLOCK / BIG BLOCK OPERATION:
WARNING! If this ECU was purchased to replace an analog ECU, the pink wire previously connected to the starter must be
removed from the starter and hooked up as described below. Failure to do so will result in possible damage to
the ECU.
WARNING! One of these two modes of operation must be selected. Failure to properly connect the pink wire will result in
system failure.
The digital ECU is programmed at the factory with fuel maps applicable for both small and big block applications. Selection between the
two modes of operation is made by hooking the pink wire in the system’s primary harness to either ground or a switched positive (+) 12
volt source. For
stock
engine sizes of 360 c.i.d or smaller, small block operation should be selected. For
stock
engine sizes of 361
c.i.d. or larger, big block operation should be selected.
After you have made the proper connection and have begun to tune the system, you may find that the selection of either small block or
big block operation for your application results in either not enough or too much fuel. Simply change the hook-up of the pink wire to
select between the two fuel maps.
SMALL BLOCK OPERATION:
Connect the pink wire located in the
PRO-JECTION
system’s harness to a good chassis or engine ground with a ring terminal.
Ensure that the crimp connection between the wire and the terminal is secure by pulling on both the terminal and the wire. Make
sure that the grounding surface is clean and located away from any direct sources of heat.
BIG BLOCK OPERATION:
Connect the pink wire located in the
PRO-JECTION
system’s harness to a switched positive (+) 12 volt source that is energized both
in the “ON” and “CRANK” positions of the ignition switch.
DO NOT
connect the pink wire directly to your vehicle’s battery.
OPERATIONAL OVERVIEW OF THE DIGITAL ECU:
This digital ECU is programmed at the factory with fuel maps applicable to both small block and big block operation. The ECU utilizes
inputs from various sensors and from the adjustment knobs located on the front of the ECU to calculate the appropriate fuel delivery to
the engine.
When the ignition is initially turned on, power is applied to the digital ECU. At this time, the ECU provides power to the fuel pump for
several seconds to prime the fuel lines and to build pressure in the fuel injection system. The digital ECU senses whether the pink wire
in the harness is attached to switched 12 volts or to ground. The ECU then internally selects whether to operate in small block or big
block mode by selecting between two fuel maps programmed into the ECU.
During cranking, the ECU begins receiving tach signals from the engine through the white wire in the wiring harness. At this time, power
is applied to the fuel pump for continuous operation and the fuel injectors are fired to deliver fuel to the engine. The appropriate amount
of fuel is calculated by taking into account; throttle position, engine coolant temperature, and an optional oxygen sensor feedback
voltage. The throttle position sensor provides information relative to how far and how fast the throttle is being opened or closed. The
oxygen sensor provides information on whether the engine is running rich or lean. Even though the oxygen sensor is heated, the ECU
will continue to operate in an open loop mode for a short period of time after initial start-up. This combined information is then used by
the ECU to adjust the fuel delivery to the engine.
The ECU also powers the fast idle solenoid, which works in direct conjunction with the engine coolant temperature sensor. During cold
starts, the fast idle solenoid will remain extended until the engine reaches an operating temperature of 75
°
F. If the engine temperature
is already above 70
°
F when starting the engine, the fast idle solenoid will remain in the extended position for a factory-set period of
time. The amount of time that the fast idle solenoid remains extended is factory set and
CAN NOT BE CHANGED
by the user. In
addition to operating the fast idle solenoid, the signal received from the engine coolant temperature sensor also provides information to
the ECU relative to enriching or leaning out the fuel delivery. When the engine is cold, more fuel will be delivered and the fuel delivery
is adjusted as the engine warms up.
During vehicle operation, the fast idle solenoid is also utilized to allow for a smoother deceleration. During deceleration, the fast idle
solenoid is activated for a pre-determined period of time and prevents stalling, as would an idle air control motor. In addition to all of the
aforementioned features, a “CLEAR FLOOD” mode has also been programmed into the ECU to aid in vehicle startup in case excessive
fuel has entered the intake manifold. Should the engine flood during start up, the clear flood mode can be initialized by turning the
ignition off, pressing the accelerator all the way to the floor, and cranking the engine until it starts.
