1 have a john deere gx345 tractor and it will not start. No fire going to the spark plugs.

This has two pulsar coils that are fired from two igniters next to the flywheel which gets it fire from a engine control module,which gets it fire from a circuit board on the rt hand side under the dash panel.
The circuit board is where you start ,you will have to a circuit board tester that's made by John Deere to test this.
Luck