Existing fuel delivery systems which use an in-tank fuel pressure regulator usually employ an energy absorbing device mounted on or near the fuel rail. The energy absorbing device serves to compensate for fuel pressure pulsations created in the fuel rail that occur as a result of sequential firing of fuel injectors operatively connected to the fuel rail. A known energy absorbing device is a damper mounted on the fuel rail. A damper of this type is disclosed in commonly-assigned, co-pending U.S. patent application Ser. No. 09/086,084, entitled "Fuel Rail Damper", filed May 28, 1998, which is incorporated herein in its entirety by reference. This known damper has an upper chamber and a lower chamber separated by a solid, flexible diaphragm. The upper chamber contains a spring that biases the diaphragm toward the lower chamber. The spring is retained in a spring seat, which engages the diaphragm. The lower chamber has an opening which allows fuel to enter from the fuel rail and contact the diaphragm. Changes in fuel pressure cause the diaphragm to adjust the volumetric capacity of the lower chamber to damp the fuel pressure changes.
Applicants have discover that over prolonged periods of operation, the known damper can exhibit reduced operative capacity. As the diaphragm adjusts the volume of the lower chamber, the spring seat reciprocates within the upper chamber. While reciprocating in the upper chamber, the spring seat can become galled from contacting the upper chamber, even though the spring seat is sized to minimize contact with the upper chamber. It is believed that a spring seat with galled surfaces can reduce operability of the damper. Thus, a damper arrangement is needed which can, under prolonged operative conditions, maintain a stable damping coefficient.