What is the working principle of a fuel injection pump?
3 Answers
The working principle of a fuel injection pump involves mechanical principles and fuel quantity regulation. Below is a partial introduction to the working principle of a fuel injection pump: 1. Mechanical Principle: The suction and pressurization of fuel by the injection pump are accomplished through the reciprocating motion of the plunger within the plunger sleeve. When the plunger is in the lower position, the two oil holes on the plunger sleeve are opened, connecting the inner cavity of the plunger sleeve with the oil passage in the pump body, allowing fuel to rapidly fill the oil chamber. When the cam pushes against the roller of the roller assembly, the plunger rises. 2. Fuel Quantity Regulation: To meet the load requirements of the diesel engine, the fuel supply of the injection pump must be adjustable from the maximum supply to zero supply. The regulation of fuel supply is achieved by simultaneously rotating all the plungers of the injection pump through the rack and rotating sleeve. Different rotation angles of the plunger result in different effective strokes of the plunger.
A few days ago, I just helped a friend diagnose the fuel pump issue in his old car – something I'm quite familiar with. The fuel pump is essentially a small electric motor submerged in gasoline inside the fuel tank. When you turn the ignition key, it starts humming to life, first building pressure by drawing fuel before sending it to the engine. Its internal turbine rotor spins rapidly, much like fan blades, sucking fuel through the inlet and forcing it out through the outlet into the fuel lines. Crucially, it relies on gasoline for cooling – running on low fuel during highway speeds can easily overheat and burn out the pump. Once, I encountered a car with acceleration stuttering; upon disassembly, we found its pump filter screen completely clogged with impurities from low-quality gasoline – a thorough cleaning fixed it. As routine maintenance, avoid driving too long with the fuel light on, and proactively replacing the fuel filter during servicing saves hassle.
I've disassembled many fuel pumps during repairs, and their design is quite ingenious. The in-tank fuel pump operates like a submarine, using gasoline for cooling and noise reduction. Its core component is a DC motor - when the key is turned to the ACC position, the relay activates it to run for 3 seconds to build up oil pressure. As the metal impeller rotates at high speed, it draws fuel from the tank bottom, compresses it, and delivers it to the engine rail at 2-6 bar pressure through the regulator. I've seen many cases where poor fuel quality caused pump core wear - when impeller clearance increases, it leads to insufficient fuel supply. Newer models even have fuel pump control modules that intelligently adjust flow rate based on throttle position, making them much more fuel-efficient than old mechanical pumps.
