The fuel pump should transport larger amounts of well filtered fuel to the in-line injector pump. To remove any possible water and air from the conveyor system.
How it works
A small, plunger type fuel pump is responsible for the fuel supply in the in-line injection pump. The filter is installed, in contrast to the distributor-injector pump, on the pressure side of the fuel pump. One distinguishes simple filters (figure on the left) and double filters, which can, when larger amounts are needed, serve as a parallel filter or, because of the higher efficiency, as a layer filter. Purged of air and dewatered, the fuel reaches, at a pressure of 1-1.5 bar, the individual pump elements of the in-line injection pump.
At temperatures under -15°C, diesel oil can possibly discard paraffin, thus becomming too thick for the fine pored filter. Using summer diesel in winter can also lead to these disturbances. Therefore, modern diesel vehicles have a regulated pre-heating. As a first aid, a longer stay in the warm workshop can help. Then, winter diesel, and perhaps additives should be filled into the tank. The addition of (normal) petrol will possibly damage the engine and only few manufacturers condone it. 10/09