Fuel retaining and collecting structure for an internal combustion engine high-pressure injection system

The structure has a number of sleeves fitted about the conduits of a supply circuit supplying fuel to the injectors of an engine. Each sleeve is tubular, and has a bellows type main body, two opposite end portions, and an outlet fitting extending from one of the end portions. The sleeves are fitted to the conduits by fitting the end portions in fluidtight manner to fittings at opposite ends of the conduits. The outlet fitting of each sleeve is then connected to a catch header by a respective connecting line, which connects the inner cavity of the main body to the catch header to enable any fuel leakage from the conduits to flow into the catch header.