an internal pulse damper for use in a fuel rail for an internal combustion engine . the damper is formed from a length of tubular metal stock having a flat oval cross - section and ends flattened by crimping to form a captive - air pillow . the end crimps are improved through use of tooling to eliminate a creased sidewall area vulnerable to stress failure in prior art pulse dampers . such tooling includes constraints to prevent the tubing sides from flaring out and forming a longitudinal crease adjacent the end crimp during squeezing - shut of the tube end .