Pressing start sets the score motor running nonstop, and play never begins.

Score motor runs on and the game never starts

Cause: The game does not see every score reel at zero: zero position switches dirty or misadjusted, a broken wire at the reel coil or reel circuit board, or a sticky reel mechanism.

Checks

• Check every reel reaches zero.
• Move the reels to zero by hand and try a new game.
• Inspect zero switches and reel wiring.

Fix

• Clean the reel mechanisms, then clean and adjust the zero switches.

Systems

• Electro-mechanical

Related tips

• Score motor keeps running after start is pressed
• 1970s Chicago Coin: motor runs on at reset
• Players 3 and 4 reset but players 1 and 2 never do at game start
• Score motor doesn't move to its next home position
• EM score motor will not stop
• Score motor runs on at start, a reel locks on: mis-gapped reel switches and solder
• EM score reel will not reset to zero
• Score motor won't stop turning at power-on: wire broken off a score reel switch stack

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part One, Clay Harrell (pinrepair.com)