Ford Ranger - all-wheel drive not functioning: front-wheel drive does not engage

If the above-mentioned defect is detected, it may be related to a defect in the vacuum system responsible for controlling the vacuum actuator (Fig. 1).

The above-mentioned vehicle has a rear-wheel drive as standard. With an all-wheel drive, the front axle is mechanically "engaged".
At that moment, the cardan or drive shaft is friction-locked to the front axle. The front drive shafts are set in motion mechanically via a vacuum actuator. The wheel hubs have a freewheel, which is automatically locked and unlocked again via an electric button.

If the all-wheel drive does not engage, special attention should be paid to the vacuum actuator or the vacuum lines. The vacuum lines lead from the actuator to the engine compartment, where they are routed via a distributor block to the switch valves (Fig. 2). Porous or broken vacuum lines will cause the actuator not to work and then, in turn, the all-wheel drive will not engage. In order to remedy this, in many cases it is simply a question of checking the lines and replacing them where necessary.