Donna - You need to do a little more testing and answer questions that have already been asked to zero in on the problem. You were asked if the motor hums when you step on the foot controller. The answer could be important.
You say that when you step on the foot controller the motor does not run. Does it do this every single time or just sometimes? If sometimes, how many times in between? One time out of 5? 10? 20?
Does it make any difference how much load is on the motor? In other words, do you get the same results with the stop motion knob released? How about taking the belt off the motor? Same result?
Have you tried a different foot controller? Same result?
If the problem is not in the foot controller check the clamping nuts on the back of the plug socket to make sure they are tight. Check to make sure the split posts in the plug socket on the machine are making a good connection with the plug on the foot controller. Spread them SLIGHTLY if necessary.
If all that checks out the problem is in the motor. First order would be to remove the brushes and clean or replace, as has been suggested. If that doesn't work, disassemble the motor and remove the armature, being careful to note the location of washers on the shaft and not to lose them. Clean the commutator ring on the armature. CAREFUL conditioning of the commutator ring will help if it is really dark. Clean the rest of the motor as best you can. Lube and reassemble. If the problem persists it is most likely a dead/shorted segment in the commutator ring or stator windings. Trust me, it is much less costly to buy a used take-off motor than to try to have your motor rewound or armature repaired.
If all the above is a foreign language to you then find someone who is well-versed in FW motor repairs. Don't go filing on that commutator ring if you don't know what you are doing.
Bottom line is if the motor won't start without a nudge every time or more often than you are willing to live with then it is motor replacement time.
David Werther
www.quilters-Connection.com