A hydraulically intensified fuel injection system comprises a hydraulic fluid accumulator, an adapter, and an injector connecting tube. The hydraulic fluid accumulator has a fluid outlet and is adapted to contain a volume of pressurized hydraulic fluid. The adapter is disposed partially within the fluid outlet of the hydraulic fluid accumulator. The adapter has an first opening provided in fluid communication with the fluid outlet of the hydraulic fluid accumulator. The first opening of the adapter has a recessed groove. The injector connecting tube is disposed at least partially within the first opening of the adapter. The injector connecting tube has an upper portion and a lower portion. The upper portion is adapted to deflect outward to reduce a gap between the injector connecting tube and the first opening of the adapter. The injector connecting tube has an second opening formed through the upper portion and the lower portion.