DIESEL COMMON RAIL
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.