Low pressure circuit for a fuel injection system

The circuit has a mechanical low pressure-prefeed pump (2) sucking fuel from a fuel tank (4), where the fuel is supplied to a low pressure region of a high pressure pump (1) via a fuel line. A dosing unit (10) is arranged in the region. A zero-delivery line with a zero-delivery throttle (14) is branched downstream of the dosing unit. An overflow line with an overflow valve (6) is branched upstream of the dosing unit. A non-return valve (16) is arranged in the zero-delivery line for selective opening or blocking of the zero-delivery line, and switched between open and closed positions. The mechanical low pressure-prefeed pump is an internal gear pump.