تنگی مسیر برگشت رگولاتور

The path by which the fuel pressure regulator bleeds off surplus fuel, restricted so the regulator cannot do its job. The regulator controls pressure by releasing fuel, so blocking its outlet disables it as effectively as breaking it — and it will test as electrically perfect throughout.

Rail pressure then runs above target with everything working correctly. The module commands the regulator to reduce pressure, the regulator opens, and nothing leaves — so the fault reads as a stuck regulator or a runaway pump. Pressure high with the regulator commanded fully open is the signature.

The restriction is usually downstream in the return circuit — a kinked line, a blocked filter or cooler in the return, or a check valve fitted the wrong way. Check the return line's flow with it disconnected at the tank end, which distinguishes a blocked path from a failed regulator in one test and is far quicker than removing the regulator.