At engine start and for preheating the fuel when temperatures are low, the rail pressure is controlled by the PCV. To heat up the fuel quickly, the high-pressure pump delivers and compresses more fuel than is needed and the excess fuel is discharged by the PCV into the fuel return.
Accumulator. An accumulator serves to increase the volume of fluid in a system. In fuel injections systems, it serves to maintain a constant pressure and dampen pressure fluctuations when fuel is injected into the combustion chamber.
Electronic Control Unit (ECU)
The ECU is the brain of the operation. It uses engine RPM and signals from different sensors to meter the fuel. It does this by telling the fuel injectors when and how long to fire. The ECU often controls other functions like the fuel pump and ignition timing.
Fuel system pressure is a result of the combination of the type of fuel pump (low flow rate or high flow rate) with a restrictive or nonrestrictive fuel system.
The fuel pressure is monitored by the engine control unit via a pressure sensor and regulated via a flow control valve installed in the pump. This fuel pressure regulator is attached directly to the high-pressure pump.
These include a bad fuel pump relay or control module, a blown fuse, a wiring fault, loose or corroded wiring connector at the pump, or even an issue with the anti-theft system. Until these other possibilities have been checked out and eliminated, the fuel pump should be the last thing that's replaced.
The fuel pump is driven by a signal that changes the power to control the speed of the motor and pressure delivered to the fuel rail during the duty cycle.
A pipe called the fuel rail supplies pressurized fuel to all of the injectors.
The overall control of the fuel injectors, high pressure pump and other parameters is handled by the engine control unit (ECU).
The fuel system is made up of the fuel tank, pump, filter and injectors or carburetor, and is responsible for delivering fuel to the engine as needed. Each component must perform flawlessly to achieve expected vehicle performance and reliability.
The injector control pressure sensor is an engine management component that is commonly found on diesel engines. As its name implies, it is an electronic sensor that monitors the fuel pressure going to the injectors.
Fundamentally, the engine ECU controls the injection of the fuel and, in petrol engines, the timing of the spark to ignite it. It determines the position of the engine's internals using a Crankshaft Position Sensor so that the injectors and ignition system are activated at precisely the correct time.
An engine control unit (ECU), also called an engine control module (ECM), is a device which controls multiple systems of an internal combustion engine in a single unit. Systems commonly controlled by an ECU include the fuel injection and ignition systems.
The fuel rail sends fuel under pressure to the engine's fuel injectors so that they can deliver fuel to the engine. The fuel rail is a manifold, or chamber that branches out into several openings. The fuel pressure regulator is a valve that is located between the fuel rail and the fuel injectors.
The sensor and the PCM help regulate the pressure to keep the fuel pressure at an ideal level for the engine in real time.
The common rail pressure sensor is located on the fuel rail. Its function is to monitor the fuel pressure in the common rail. Sensor is used by the ECM as a part of the calculation for the % duty cycle applied to the Fuel Pressure Control Valve and Fuel Quantity Control Valve.
The injector body consists of a solenoid-actuated pintle and needle-valve assembly. The control unit sends an electrical impulse that activates the solenoid, causing the pintle to move inward off the seat and allow the fuel to flow.
They are powered by a 12 V supply either from the fuel injection relay or the ECM. In short, injectors are solenoid operated valves that use Pulse Width Modulated (PWM) signals from the Engine Control Unit to open or close a valve that permits or blocks fuel flow to the engine.
On older engines where the injectors are all fired simultaneously, the good injectors can often compensate for one or two bad injectors. Even so, for the engine to run right, fuel pressure to the injectors is critical as is the volume of fuel delivered by each injector when it fires.
Running the vehicle on low fuel often can damage the fuel pump over time, which affects the fuel pressure. Fuel cools the fuel pump, and less fuel means there's a greater chance fuel pump components can overheat or wear out. Low fuel can also draw air into the pump, preventing a consistent flow of fuel.
The fuel pressure regulator sees that the fuel rail builds up enough pressure to support the vehicle's fuel injector system with the right amount of fuel. Without the fuel pressure regulator, the fuel will go straight through your car's system and never reach the injectors.
The Fuel Pump Control Module communicates with the Engine Control Module over the vehicle's Local Area Network. The ECM provides a 5-volt enable signal to the FPCM to enable fuel pump operation. A enable command is also provided initially for 2 seconds when the ignition switch is placed into the RUN position.
If there is still no pressure, then replace the fuel filter and retest. If nothing after that, then the fuel pressure regulator is not working and needs replacing. If you get pressure to the rail, then there could be a problem with the injectors; they may be either dirty or plugged up.