إمداد التفريغ غير كافٍ

Not enough vacuum available to operate the devices that depend on it. It is a supply fault affecting several actuators at once, which is its diagnostic signature — a group of vacuum-operated components all behaving weakly points at the supply rather than at all of them failing together.

Turbocharged petrol and diesel engines generate little manifold vacuum, so they carry an auxiliary pump and a reservoir. A failing pump, a leaking reservoir, or a failed check valve leaves the whole system short, and the devices furthest from the supply suffer first.

A leak anywhere in the network reduces it for everything. So the search is for the leak rather than for a failed actuator: perished lines, a split tee, a torn diaphragm in any one actuator, or a brake servo that has failed. Measure available vacuum at the reservoir with a gauge and compare it against specification — that tells you immediately whether you are looking for a supply problem or a device problem.