If you have just made a fuel system repair, changed the fuel filter or the tank has run out of gas, your engine might not start so could be due to a needs-to-be-primed For this reason the very first thing we would recommend you try and prime your fuel pump. To ensure that fuel is delivered from the tank to the engine appropriately, the fuel pump must be primed to keep air bubbles from interrupting flow of fuel. This is a common sign of a fuel pump that needs to be primed and in layman terms, its called "crank-no-start" meaning the engine cranks but does not start. The answer is because the system has lost the pressure to inject fuel, plain and simple.
Air is continuously drawn in through small leaks or can enter the fuel system when it has been opened for repairs, or during times of low fuel levels. Electric fuel pumps in most modern vehicles … rely on pressurization for peak efficiency. Most cars will prime themselves when the key is turned to "on," and a faint hum or buzz sound can be heard as the pump primes it down in the tank. Usually this process takes about 2-3 seconds. If you do not hear that, then the pump might not be priming... could be a relay/fuse/wiring problem.
Fuel pressure gauge — Using a fuel pressure you can check if the need to prime your fuel pump. Although fuel pressure is going to be specific to the make and model of the vehicle, most fuel- injected systems operate from 40 to 70 psi. If the pressure is lower than meant to, this indicates the pump is simply not priming properly. Then there is also my favorite report 2020 of a national institute for Automotive service Excellence (ASE) reveals that low fuel pressure caused 10% of the modern car engine not to run while color-coded on the other side as the importance of running a proper and perfect priming.
The car will also not prime its pump if the fuel pump relay is bad or the fuse to it is blown. Checking or replacing these parts can correct the problem. Fuses generally £1 to £5 and Fuel Pump Relay about $20 to $50 which depends on the car. The issue could also be in the fuel pump itself if the relay or fuse checks out, but the pump doesn't prime.
The system might have some air in it, if the fuel system was worked on or serviced recently. Diesel engines: Diesel engines are particularly prone to having air enter the fuel lines. Electric fuel pump primed automatically, manual priming may be required on some vehicles. Refer always to your vehicle's service manual for the correct method of priming the fuel pump.
If everyone is moving forward together, then success takes care of itself. — Henry Ford This translates interestingly to automotive systems where all components need to work in concert with each other — if the fuel pump is not primed, everything else in the engine system will suffer.
So, in short, if your car has any signs of needing a fuel pump prime such as having issues starting the engine, experiencing low fuel pressure, or air in the fuel line then you probably need to do so. For further information on how to diagnose or replace your fuel pump visit Fuel Pump