The figure schematically shows the movement of fuel in the diesel injection system: from the tank (7) fuel through the supply pipeline (8) enters the fuel filter (1). The purified diesel fuel is then sucked into the high pressure fuel pump (injection pump) (2). Excess is discharged through a thin outlet (3) into the outlet pipeline (4). Through the high pressure fuel line (6) high pressure fuel enters the injector (5). A small amount of fuel that does not pass through the atomizer needle and is not injected returns through the bleed line back to the tank.
High pressure sprayer
The injection pressure of the injectors must exceed the compression pressure of the engine. A diesel runs at a higher compression than a gasoline-powered car, so the diesel injector pressure is about 100 times higher than the injector pressure of a gasoline injection system.
Fuel supply
The course of the fuel lines is shown schematically in the figure below. From the tank, the pipeline runs along the bottom of the car to the fuel filter on the right in the engine compartment. Diesel fuel is cleaned in the filter and then sucked in by the high pressure fuel pump (injection pump). The Renault 19 diesel is equipped with a Bosch fuel pump in accordance with US 87 and 91441/EEC respectively. High pressure fuel pump installed on UNECE 1504/1505 engines (injection pump) from CAV/Roto or Lucas.
High pressure fuel pump (injection pump) supplies diesel fuel through robust high-pressure fuel lines with overpressure up to 140 bar to 4 injectors, more fuel is injected than is used in the injectors. Therefore, the excess is discharged through the outlet pipe back to the tank. The injectors also do not inject the entire volume of supplied fuel into the combustion chambers.
Excess fuel serves to lubricate the moving parts of the high pressure fuel pump (injection pump) and injectors. To remove excess fuel, the nozzles have return pipes and are interconnected by hoses called oil leakage hoses. From the right nozzle, when viewed in the direction of travel (cylinder 4), the fuel is discharged through the drain pipe back to the tank. One of the two outlet pipes of the nozzle of the first cylinder does not end with a drain pipe, but with a plug.
Removal of air from the power system
An empty tank used to be a real nightmare for the owner of a car with a diesel engine. Cause: If the intake pipes of the injection system were emptied, it was very difficult for the pump to re-suck in the fuel and supply it to the injectors.
For the owner of a diesel Renault, an empty tank is no longer a big problem, as his high-pressure fuel pump (injection pump) is self-priming. It is necessary to have a good battery and turn the engine with the starter until diesel fuel is pumped up.
Since the fuel filter also remains without fuel when the tank is empty, it is necessary to pump fuel after refueling using the fuel priming pump located on top of the fuel filter until air bubbles no longer come out. Then start the engine.
Note. Recommendations: The plug on the last injector mentioned above may be leaking, resulting in fuel leakage and engine malfunction. Check to see if fuel is leaking from there while the engine is running, or if it is spewing at all. Replace defective plug. The hollow bolts of the supply and return pipes must not be interchanged on the high pressure fuel pump.
Note. This can happen, for example, if you want to replace fuel lines. Both bolts have the same thread but different hole diameters. Hollow bolt with smaller inner diameter refers to the fuel outlet. Written on his head «OUT». Reversing the bolts will cause the pump to overheat and cause engine malfunction.