Fuel Metering

DESCRIPTION AND OPERATION
The Engine Control Module (ECM) controls the Fuel Delivery System during normal driving conditions.

The Intake Manifold function, like that of a diesel, is used only to allow air into the Engine. The fuel is injected by separate Injectors, mounted over the Intake Manifold.

The air drawn into the Engine is sensed by the Air Flow Sensor. This sensor generates the voltage according to the flow of the air drawn into the Engine. The changing voltage is transformed into an electric signal and provided to the ECM. After receiving signals sent from the Air Flow Sensor, and others, the ECM determines an appropriate fuel injection pulse width, referring to the programmed data, and sends this information to the Fuel Injector Valves to effect an appropriate air/fuel ratio.

In the Port Fuel Injection System, the Injectors turn on at every Crankshaft revolution. The ECM controls the Injector on time so that the correct amount of fuel is metered depending on driving conditions.

Two interchangeable 0-Rings are used on the Injector that must be inspected when the Injectors are removed. Check 0-Rings for cuts or other damage and replace as necessary.

The Fuel Rail is attached to the top of the Intake Manifold and supplies fuel to all the Injectors. Fuel is recirculated through the Rail continually while the Engine is running. This removes air and vapors from the fuel as well as keeping the fuel cool during hot weather operation.

The fuel pressure regulator, mounted on the Common Chamber, maintains a pressure differential across the Injectors under all operating conditions. It controls the amount of fuel that is recirculated back to the Fuel Tank, based on engine demand.

Acceleration Mode
The Powertrain Control Module (PCM) provides extra fuel when it detects a rapid increase in the throttle position and the air flow.

Accelerator Controls
The accelerator control system is a cable-type system with specific linkage adjustments.

Battery Voltage Correction Mode
When battery voltage is low, the PCM will compensate for the weak spark by increasing the following:
- The amount of fuel delivered.
- The idle RPM.
- Ignition dwell time.

Camshaft Position (CMP) Signal
The PCM uses this signal to determine the position of the number 1 piston during its power stroke, allowing the PCM to calculate true sequential multiport fuel injection (SFI). Loss of this signal will set a DTC PO341. If the Camshaft Position (CMP) signal is lost while the engine is running, the fuel injection system will shift to a calculated sequential fuel injection based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated sequential mode as long as the fault is present, with a 1-in-4 chance of being correct.

Clear Flood Mode
Clear a flooded engine by pushing the accelerator pedal down all the way. The PCM then de-energizes the fuel injectors. The PCM holds the fuel injectors de-energized as long as the throttle remains above 80% and the engine speed is below 800 RPM. If the throttle position becomes less than 80%, the PCM again begins to pulse the injectors "ON" and "OFF", allowing fuel into the cylinders.

Deceleration Mode
The PCM reduces the amount of fuel injected when it detects a decrease in the throttle position and the air flow. When deceleration is very fast, the PCM may cut off fuel completely for short periods.

Engine Speed/vehicle Speed/fuel Disable Mode
The PCM monitors engine speed. It turns off the fuel injectors when the engine speed increases above 6000 RPM. The fuel injectors are turned back on when engine speed decreases below 5750 RPM.

Fuel Cutoff Mode
No fuel is delivered by the fuel injectors when the ignition is "OFF". This prevents engine run-on. In addition, the PCM suspends fuel delivery if no reference pulses are detected (engine not running) to prevent engine flooding.