Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Control System
The basic function of the fuel control system is to control fuel delivery to the engine. Fuel is delivered to the engine by individual fuel injectors mounted in the intake manifold near each intake valve. The main control sensor of this system is the O2 sensor. The O2 sensor indicates to the ECM the oxygen content of exhaust gases. The ECM then adjusts the air/fuel ratio to the engine by controlling injector on time.
The fuel control system consists of the following components: fuel injectors, throttle body, fuel rail, fuel pressure regulator, idle air control valve, fuel pump and fuel pump relay. The fuel control system starts with the fuel in fuel tank. An electric fuel pump, located in fuel tank with fuel gauge 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.
The pressure regulator, located on the fuel rail, regulates fuel pressure to injectors. Excess fuel is returned to the fuel tank by a separate return line. In order for fuel injectors to supply a precise amount of fuel at the command of the ECM, the fuel system maintains a constant pressure of approximately 34-46 psi (2.4-3.2 kg/cm2 ) at injectors. The pressure regulator compensates for engine load by increasing fuel pressure as manifold pressure drops.
When the ignition is turned on, ECM will turn on the in-tank fuel pump. It will remain on as long as the engine is cranking or running. ECM uses distributor reference pulses to determine when engine is running. The ECM also uses the oil pressure switch as a back-up system to determine when engine is running.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.