as fuel injection systems typically require significantly higher fuel pressure to (more) fully atomize the fuel.
Most electric pumps are installed in the fuel tank, where they are submerged in the fuel until the tank is nearly empty, because electric pumps are generally “pusher” pumps rather than “puller” pumps. (They typically operate based on a spinning paddle wheel, which is efficient at pushing fuel, but does not do well drawing fuel into itself.) Electric fuel pumps often supply fuel at 45–60 psi, though some direct injection systems require hundreds or even thousands of psi. Modern diesel systems often operate on as much as 3000 psi.
Older, mechanical fuel pumps that were attached to the engine typically had a diaphragm that was operated by a pushrod that rode along an eccentric on the camshaft (or an eccentric bolted to the front of the camshaft). The diaphragm created a low pressure “vacuum” that was moderately effective at drawing fuel from the tank to the engine, then it also created positive displacement to push the fuel to the carburetor at modest pressures, typically around 5–7 psi.
When the driver turns the ignition key on, the powertrain control module (PCM) energizes a relay that supplies voltage to the fuel pump. The motor inside the pump starts to spin and runs for a few seconds to build pressure in the fuel system. A timer in the PCM limits how long the pump will run until the engine starts.
Fuel is drawn into the pump through an inlet tube and mesh filter sock (which helps keep rust and dirt out of the pump). The fuel then exits the pump through a one-way check valve (which maintains residual pressure in the system when the pump is not running), and is pushed toward the engine through the fuel line and filter.
The fuel pump has its 12VDC feeding wiring on top and you can see this plug on top of fuel tank. Fuel pump will pump fuel into engine when ignition key is on. Fuel will supply thru feeding line (steel ) which runs under your car’s floor then come back to fuel tank by the return line ( also made of steel with different size ). Make story short, fuel is pumped to engine thru fuel rail in which it is fed to fuel injectors then return to fuel tank and keep going like circulation. Electrical signal given by your gas pedal’s position will be fed into computer. Car computer module will calculate the ratio of mixed air and fuel needed respect to your gas pedal positions. This command will determine how much or how rich ratio air and fuel for your fuel injectors . In fact, this fuel system alone would have more complicated circuitry in real life。
