Car (South Africa) - - TECH -

Early diesel en­gines sup­plied fuel to the me­chan­i­cal, spring­op­er­ated in­jec­tors via an in­jec­tor pump that had a plunger for each in­jec­tor. This pump al­most re­sem­bled a small en­gine, with each plunger a mini pis­ton, and was com­plex in op­er­a­tion and ex­tremely costly to re­place. The an­swer was a com­mon rail sup­ply­ing all the elec­tri­cally con­trolled in­jec­tors with diesel at a con­trolled pres­sure. This was in­tro­duced in pro­duc­tion ve­hi­cles in the Nineties. A com­mon-rail sys­tem con­sists of a diesel pump sup­ply­ing the fuel at pres­sures of up to 2 000 bar, the com­mon rail with rail-pres­sure sen­sor, a pres­sure-re­lief valve and pipes feed­ing the in­jec­tors. The ECU con­trols the fuel pres­sure in the rail and trig­gers each in­jec­tor when it is time to in­ject. The amount of diesel in­jected is a func­tion of rail pres­sure and in­jec­tor-open­ing times. The com­mon-rail sys­tem is far sim­pler and more pre­cise than the older plunger-type in­jec­tor pump.

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