Diesel supply pump HP3 components and their functions on common rail engine

On the common rail diesel engine, the supply pump functions as a source of high-pressure fuel. High-pressure fuel will then be channeled to the common rail pipe and injected into the combustion chamber by the injector.

The supply pump connects to the engine in various ways to make it work. Some use a timing belt to rotate the supply pump pulley, and some used gear to hook it up.

Yes, at the end of the supply pump, there is a pulley connected to the engine. When the engine rotates, the supply pump also rotates directly to produce high-pressure fuel, needed by the common rail system diesel engine.

The following article will share information about the supply pump components and their functions on the common rail diesel engines, especially for the HP3 type. See information about the supply pump components below.

1. Feed pump

The first component of the HP3 type supply pump is the Feed Pump. The feed pump function is to suck fuel from the fuel tank and press it into the main injection pump chamber. The main injection pump chamber contains the plunger so that the fuel pressure can be increased even higher according to the injection needs of the common rail diesel engine.

The fuel flowing from the fuel tank is filtered using the fuel filter before entering the feed pump. The fuel will pass through the Suction Control Valve (SCV) and enter the injection pump chamber containing the plunger from the feed pump.

The feed pump on the HP3 supply pump used the trochoid type. Pay attention to the shape of the trochoid-type feed pump in the picture below.

The inner rotor component of the feed pump connects to a drive shaft inside the supply pump. When the drive shaft rotates, the inner rotor will rotate as well as move the outer rotor.

At this time, diesel fuel from the fuel tank channel and inlet port will be sucked in through the suction port and pumped out through the discharge port, which will go to the SCV and plunger.

When there are increases in the engine's rotational speed, this will cause the feed pump rotation will also increase. Then, the feed pump fits with a regulating valve to prevent excessive fuel pressure due to increased engine speed,

The regulating valve will regulate the fuel pressure from the feed pump to remain stable at a certain pressure limit that the manufacturer has set.

When the fuel pressure is excessive, the regulating valve will open due to pressure. Opening the valve will reduce the pressure in the feed pump. The fuel flowing through the regulating valve is fed back again into the feed pump. So the feed pump can pump it into the plunger.

2. Suction Control Valve (SCV)

The second component of the HP3 type supply pump is the Suction Control Valve (SCV). SCV is an actuator on a common rail engine connected to the engine ECM and works based on commands from the ECM (Engine Control Module).

SCV functions to regulate the amount of diesel fuel coming from the feed pump to the plunger so that the fuel pressure pumped by the supply pump to the common rail pipe can always be stable and constant according to the engine's needs.

The SCV on this supply pump shapes like a solenoid valve. Inside, a coil (copper coil) will become a magnet when an electric current is applied. Inside the SCV, there is also an iron rod (armature) connected to the valve. When there is an electric current from the ECM to the SCV coil, the armature will be attracted and open the valve.

SCV works in a duty ratio based on the output signal from the ECM, which is in the form of a frequency wave and flows constantly. The frequency value of this wave will affect the size of the valve opening on the SCV.

As the frequency value increases, the valve opening will decrease and get smaller. Meanwhile, the valve opening will increase, and the valve opens wider when the frequency value decreases.

Read also:

3. Pump Unit

The third component of the HP3 type supply pump is the Pump Unit. This pump unit is a part that functions to produce high-pressure fuel, which will pump to the common rail pipe.

This pump unit consists of 3 parts, namely:

Eccentric cam: Eccentric cam is a driveshaft in which a cam has an asymmetrical position in the middle (slightly protruding to one side). Eccentric cam mounted in the middle of the cam ring.
Ring cam: Ring cam box-shaped with a hole in the middle. In this hole, the eccentric cam is installed, so when the drive shaft rotates, the protrusion on the eccentric cam will move and push the cam ring to create a pump-like movement.
Plunger: There are two plungers on this HP3-type supply pump, located opposite and connected to the ring cam. The plunger works based on the pumping motion that occurs in the ring cam. This plunger will push and pump diesel fuel to create high-pressure fuel.

Pay attention to how the pump unit component is pumping fuel in the picture below.

4. Delivery valve

The fourth component of the HP3 type supply pump is the delivery valve. This delivery valve consists of 3 components, namely spring, check ball, and holder. Each component works into a single unit called the delivery valve.

This delivery valve serves to drain the pressurized fuel produced by the plunger to the common rail pipe. In addition, this delivery valve is also used to prevent compressed fuel in the common rail pipe from re-entering the plunger.

That way, the more fuel that enters the common rail pipe, the more fuel pressure will increase. Pay attention to the position of the delivery valve in the picture below.

5. Fuel temperature sensor

The last component of the HP3 type supply pump is the Fuel temperature sensor. This fuel temperature sensor functions to measure the fuel temperature that flowing in the supply pump. Fuel temperature will send data in the form of electrical voltage used by the ECM as the fuel temperature value.

As a sensor, fuel temperature uses an electronic component called a thermistor that works when there is a temperature change. When the fuel temperature is low, the resistance (resistance) on the thermistor will be large. In contrast, when the fuel temperature is high, the resistance value will decrease.

That way, the voltage that flows will also change according to the resistance value generated due to temperature changes in the fuel. The ECM then uses this change in voltage value as fuel temperature data.