Diesel Engine Troubleshooting

Rail Flow Damper

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The flow damper reduces the pressure pulsations of the fuel in the pressurized pipe and supplies fuel to the injectors at a stabilized pressure. The flow damper also presents abnormal discharge of fuel by shutting off the fuel passage in the event of excess fuel discharge, for example due to fuel leaking from an injection pipe or injector. Some flow dampers combine a piston and ball, and some have only a piston.

pic1 67 Rail Flow Damper

Operation of Piston-and-Ball Type
– When a pressure pulse occurs in a high-pressure pipe, the resistance of it passing through the orifice disrupts the balance between the rail side and injector side pressures, so the piston and ball move to the injector side, absorbing the pressure pulse. With normal pressure pulses, since the rail side and injector side pressures are soon balanced, the piston and ball are pushed back to the rail side by the spring. If there is an abnormal discharge, for example due to an injector side fuel leak, the amount of fuel passing through the orifice cannot be balanced out and the piston presses the ball against the seat, so the passage for fuel to the injector is shut off.

pic1 68 Rail Flow Damper

Operation of Piston-Only Type
– The piston contacts the seat directly and the piston shuts off the fuel passage directly. Operation is the same as for the piston-and-ball type.

pic1 69 Rail Flow Damper

Written by Jack

March 7th, 2019 at 12:57 am

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