The high pressure fuel pump cannot be repaired or overhauled. If the pump is not functioning properly, it must be replaced. All engines are equipped with Roto-Diesel (Lucas-CAV) high-pressure fuel pumps, which, however, were modified several times between 1983 and 1992, meaning that it is not possible to install a pump from an earlier model on an engine of a later model.
Adjustment, as well as removal and installation of the high-pressure fuel pump, require special tools and should not be attempted without such tools. Below is a description of the work that can only be performed with a special tool.
Diesel engines operate either with direct injection or with fuel injection into the intake manifold or pre-chamber. On the D9B diesel engine, fuel is injected into a pre-chamber in the cylinder head, connected to the main combustion chamber. Fuel combustion begins in the pre-combustion chamber and, under the influence of increasing pressure, burning fuel particles enter the main combustion chamber, where they are completely burned.
With the development of diesel engines, there have been some innovations that deserve a brief mention.
Fuel filter and fuel heater: Fuel filtration and heating are functions of the engine. Figure 362 shows the functional diagram of the fuel heating device. The fuel is heated by the coolant flowing through the channels in the heating unit (4) in the cooling system fitting. The thermostatic element regulates the amount of fuel heated. The degree of heating depends on the ambient temperature. At temperatures below 15°C, all fuel from the fuel tank flows through the heating unit, where it is heated, and then goes to the filter, from where it is supplied to the high-pressure fuel pump. When the temperature rises to values from 15°C to 35°C, the thermostat valve is not fully open. In this case, only part of the fuel enters the filter through the described path. The remaining fuel is fed directly to the filter and from there through the high-pressure fuel pump (2) to the engine (3).
Figure 362. Functional diagram of the fuel heating device. 1. Fuel filter; 2. High-pressure fuel pump; 3. Engine; 4. Heating unit; 5. Fuel flow from the fuel tank
(Text taken from the website peugeotbook.ru)