Fuel Injection System

This engine utilizes a Sequential Multiport Fuel Injection (SFI) system. This fuel system is classified as a multi-point, pulse time, volume air flow system.

Components of the fuel supply system include:
- Fuel pump
- Fuel filter
- Fuel injection supply manifolds
- Fuel pressure relief valve
- Fuel pressure regulator
- Fuel injectors
- Inertia Fuel Shutoff (IFS) switch

The fuel pump is mounted in the fuel tank to minimize operating noise. It supplies filtered, pressurized fuel to each fuel injector through the fuel injection supply manifold. Fuel pressure is regulated by the fuel pressure regulator, located on the fuel return side of the fuel injection supply manifold.

A fuel pressure relief valve allows operational testing of pressure and bleed down. The valve is located in the return side of the fuel injection supply manifold near the fuel injector manifold connector.

The fuel charging wiring is supplied with voltage from the Powertrain Control Module (PCM). The fuel charging wiring for the two fuel injection supply manifolds is mounted across the top of the fuel injectors.

The SFI system works in conjunction with the engine control system. This engine control system consists of the PCM, various sensors, and switches. These sensors and switches send input signals to the PCM. Based upon these input signals, the PCM controls the timing and duration (pulse width) for each injection of fuel. If at any time, the PCM malfunctions, or the battery voltage drops to an abnormal level, fuel injection will occur for all cylinders simultaneously once every two revolutions of the crankshaft.

FUEL INJECTION TIMING

Injection Timing:

When the engine is cranking, fuel is supplied to all the cylinders simultaneously, one injection for each fuel injector per crankshaft revolution. Between engine idle speed and 7,500 rpm, during PCM or Camshaft Position Sensor (CMP) failure, fuel is supplied through the fuel injectors once every two crankshaft revolutions (one injection per cycle).

To prevent overspeeding and possible engine damage, the fuel supply is cut if engine speed exceeds 7,500 rpm. If engine speed momentarily exceeds 7,500 rpm, the fuel supply is interrupted until the engine speed drops below 7,500 rpm. The fuel supply will also be interrupted if the engine speed exceeds 5,500 rpm and the coolant temperature is below -15°C (5°F).

To improve fuel economy during high-speed deceleration, the fuel supply is interrupted, based on input from various sensors and switches, until the specified engine speed is reached.

To facilitate starting the engine if the spark plugs become fouled (engine flooded), fuel injection is cut if the throttle valve is held wide-open while cranking. This allows the spark plugs to dry and purges excess fuel from the cylinders.