Yanmar Ypd-Mp2, Ypd-Mp4 Service Manual

Yanmar Ypd-Mp2, Ypd-Mp4 Service Manual
Yanmar Fuel Injection Ypd-Mp2, Ypd-Mp4 Series Service Manual

This document describes the features, disassembly, reassembly and adjustment procedure of the fuel injection unit (Model YPD-MP2,MP4) for Yanmar Diesel Engine Model TNV. Fuel injection unit is an essential mechanism of diesel engines, and thus, has to be designed to allow fine adjustment to the engine load.

Therefore, the components of the fuel injection pumps are required to be given high-precision. To meet this requirement, we process and assemble them very accurately.

Accordingly, when performing disassembly and adjustment works in the market, keep the workbenches and their environment clean to surely prevent dirt and dust from attaching to the components of the unit, and take special care that the components are not rusted.

Please note that the specifications of the components are revised to improve the quality of the product, and thus, the details of the changed specifications will be notified through the correction table every time the change occurs.

Outline of MP pump
MP pump is a fuel injection pump that has been newly developed to be installed on Yanmar direct injection system diesel engines for the purpose of complying with the regulation for the exhaust gas emission that are becoming tighter in the future. The fuel injection pump is a fuel distribution type pump that supplies fuel to each cylinder of the engine through a distribution shaft by using a single plunger unlike conventional rail system or distribution system pumps.

Yanmar Fuel Injection Ypd-Mp4 Service Manual 
Yanmar distribution type fuel injection pump YPD-MP consists of a hydraulic head that is equipped with a single plunger, a single distribution shaft, and delivery valves for each individual cylinders, a pump housing that includes camshafts, and a governor, all of which are integrated into the main unit of the pump.

For the feed of the fuel, the plunger moves up / down and the distribution shaft rotates with the revolution of the camshaft to distribute the fuel among the cylinders individually.

Specifically, one revolution of camshaft completes three cycles (for three cylinder engine) of a process, including switching over to the high pressure flow path to each cylinder with the distribution shaft, opening delivery valve, high pressure pipe, fuel injection valve, and engine cylinders in this order. This process is repeated by the revolution of the camshaft.

Yanmar Fuel Injection Service Manual 
Usage condition of diesel engines are extremely varied,with a wide range of loads and speeds.The governor plays an important role in the operation of the engine by quickly adjusting the position of the control rack to control the amount of fuel injected, according to changes of engine speed. It also automatically controls the engine to prevent engine speed from exceeding the maximum ,and keeps the engine from stopping.

The governor weight mounted on the end of the fuel injection pump cam shaft rotates around the governor support pin, driven by the cam shaft, and is forced outwards by the centrifugal force acting on the weight. The thrust force acting on the cam shaft due to this centrifugal force acts on the lower part of the tension lever through the sleeve A starting excess fuel spring is mounted on the bottom of the tension lever. 0ne end of the governor spring is hooked to the right upper end of the tension lever, and the other end to the spring lever of the control lever shaft.

As the spring lever and control lever are mounted on the same shaft, when the control lever is turned towards full, the governor spring is pulled and the load gradually increases. Since the tension lever can move freely around the governor shaft on the player bearing, as speed increases and the shifter is pushed to the left,the tension lever rotates clockwise, and when speed decreases,the tension lever rotates counterclockwise.

The governor lever rotates smoothly on the second shaft installed on the tension leveb. The bottom part of this lever is in contact with the sleeve through the shifter, which is in contact with the bottom of the tension lever through the excess fuel spring. It therefore moves with the tension lever according to increases/decreases in engine speed.

The top of the governor lever is connected to the fuel pump control rack through the governor link. The movement of the lever controls the volume of fuel injected by the pump. When speed increases the lever rotates clockwise to cause the control rack to reduce fuel and when speed decreases the lever rotates counterclockwise to cause the control rack to increase fuel, thus engine speed is controlled. The top of the tension lever comes in contact with the stopper built into the top of the governor case to limit the maximum fuel injection volume.

Yanmar Fuel Injection Ypd-Mp2 Service Manual 
Moving the control lever to the max.speed position pulls the governor spring, and moves the tension lever until it comes in contact with the control stopper. When this is done,the excess fuel spring provided in between the tension lever and governor lever holds the control rack at the maximum starting injection volume position RA-B.

After the engine is started, the excess fuel spring is compressed when the centrifugal force of the governor weight overcomes the set of the excess fuel spring as speed exceeds Nb, speed goes from B to C' (on models with angleich spring ) or B to C(on models without angleich spring ). The rack reaches the position of Rc where the governor lever and tension lever are interlocked.