A spring-return solenoid valve works on two opposing forces. Energising the coil creates a magnetic force that shifts the spool to its actuated position, and an internal return spring stores energy so that it can push the spool back to rest when the coil is de-energised.

This spring is the only element that resets the valve; the electromagnet acts in one direction only.

If the return spring is damaged or missing, there is no restoring force left. When power is removed, nothing pushes the spool back, so the valve cannot return to its original position.

In a sequence-control circuit each step depends on valves resetting on cue, so a valve stuck in its actuated state breaks the timed sequence and the actuator does not return as programmed.

Electrical consumption (option 1) is set by the coil, not the spring, so a faulty spring does not lower it.

The air supply is not guaranteed for all cycles (option 3); rather the valve jams in one state, so flow is fixed wrongly, not usefully ensured.

Losing the spring cannot make the valve cycle faster or improve speed (option 4); it prevents cycling altogether.

Hence, the answer is The valve may fail to return to its original position after de-energization.