A high pressure gaseous fuel supply system for an internal combustion engine and a method of sealing connections between components to prevent leakage of a high pressure gaseous fuel

A high-pressure fuel system for supplying a gaseous fuel to an internal combustion engine, wherein gasesous fuel pressure within the system is at least 17 MPa during normal operation. The system comprises a number of components and conduits and at least one resilient member for sealing at an interface between two components. The resilient member consists essentially of thermoplastic polyurethane. A method is also provided of sealing between components that contain gaseous fluids at pressures that can be above 17 MPa, wherein the gaseous fluids routinely undergo rapid reductions in pressure. The method comprises disposing a resilient member at an interface between said components, the resilient member consisting essentially of thermoplastic polyurethane. Gas pressure fluctuations can occur during operation of the components or when the high-pressure gas is vented from the components upon shut down of the high-pressure system. A particularly suitable application for the present method is high-pressure gaseous fuel supply systems for internal combustion engines.