Arked battery to motor

[Puf454]

Hi, I used my cart to jump start my lawn tractor.
While doing so, the positive lead touch the motor in the cart and has not started since.
It's in the shop and they advised the coil in stuffed. Replaced coil and now have spark but will not start.
It will run if they manually pour gas into the engine.
They have advised they believe the ecu needs replacing as it is not talking to the injector.
New ecu is like $3,000 after spending $300 on a new coil!!!!!
I am finding it hard to believe it is the ecu or the coil as it was not even running at the time of the incident.
Any one have any ideas?