This is the time of year we get calls about "My Stop works fine in the pits but will not open going down the race track." The next question is "Is my solenoid getting weak?" Answer is 99% of the time, NO!!! Usually it is an electrical problem "bad connection", weak battery etc.
This can be solved by making sure your T.S. circuit is 10 GA wire including voltage to your timer/delay box and that no other circuits are taken off that lead. If that doesn't solve the problem, use a Bosch Relay and use the timer to control the coil on the relay and run your 10 GA wire from your large wire at the starter to the Bosch Relay and 10 GA to the T.S., making sure that you have a 10 GA wire to a good ground. Also, if you still have difficulty, you may consider an alternator to keep voltage up. Questions, call or e-mail.