Machine is making a grinding noise when the foot pedal is set in low speed

SOURCE: SINGER LIMITED EDITION-MODEL 6268

More than likely you need a pneumatic transducer. It's the part that your air tube connects to and that is what actually makes your machine run.
sewman7

SOURCE: my machine has power, but foot pedal only makes needle go slowly

sounds like the contact in the foot peddle has failed try a new peddle

SOURCE: the foot pedal does not make the machine sew but

you did not say the model or maker of machine but from my experience, their are some model from brother where the belt slips off the motor pulley, this could be your problem.

SOURCE: My Viking 5710 starts to sew without any pressure on foot pedal

Mine does the exact same thing. I think the problem might lie in the cord to the foot pedal. The cord packs into the foot pedal for storage, which forces the cord to to remain bent during storage. I believe the wires in mind became damaged and broken so I took it apart and reconnected the wires at the spot where the connector meets with the wires. But I still don't leave it plugged in if I'm not using it, it could be a fire hazard.

SOURCE: foot pedal not working

yes, it is possible that the foot pedal can go out,, it would be a good
idea to have the foot pedal checked at a repair shop to see for
sure

Testimonial: "I went to sewing machine store today and the pedal checked out as dying, so ordered a new one. Thx again!"