motor starts when i dissconnect main engine harness and jump starter

[old evin]

disconnect harness jump start it fires. connect harness turn key crank crank crank. put in a new ignition switch same thing. any ideas

 

[emdsapmgr]

You don't mention the hp or year of your engine...Does your control box have an emergency stop (lanyard) switch?

 

[Chris1956]

Sounds like the ign killer wire (usually black/yellow) is grounded somewhere.

 

[Scott Danforth]

or the tach wire is grounded