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Rail pressure bleeding away while the vehicle stands, so the first start of the day is long. A healthy high pressure system holds much of its pressure for hours, which is what makes a quick restart possible; a system that empties has to build from nothing on the starter.

The complaint is a hard start after standing and an easy one after a short stop — the clearest possible signature, and one owners describe accurately. Where it leaks decides the repair: a leaking injector returns fuel to the tank quietly, a failed non-return valve in the pump lets the rail drain back, and a leaking high pressure line shows externally. Measure how quickly rail pressure decays after shutdown, then isolate by blocking the return — that separates injectors from pump in one test.