5000,S Turbo Diesel L5-1986cc 2.0L DSL SOHC Turbo (DE) (1982)
Diesel MFI Pump: Description and Operation
Pressure Valve Return Restriction
Because of the necessary and precise pressure relief at the end of the injection pulse, pressure waves are generated. In turn these are reflected at the
pressure valve, and lead to another opening of the injection nozzle or vacuum conditions in the injector line. The result is post-injection of fuel, with
attendant increases in exhaust emissions or wear-inducing cavitation in the injection lines or nozzles.
To prevent such reflections, a restriction bore, effective only in the return direction, is added to the pressure valve. This restriction consists of a valve
plate and pressure spring; during delivery it has no effect, but as fuel tries to return it imposes flow resistance and a damping effect is the result.