Won't start / No fire

[victoriffic]

I have a 2007 Scag Wildcat, which has been a perfect piece of equipment untill now. After sitting in the barn all winter, the original battery was dead. I jump started the engine (26 hp Kaw ) and it started right up. When I disconnected the jumper cables it died......after that it will not crank nor is their any spark when I jump across the starter with the key on.
All the interlocks check good, I found a diode on the wiring diagram and finally found it buried in the wiring harness, it test good. The starter relay is good and I even swaped it with another to verify this.
Grass is 12" tall......Help

 

[BKBrown]

Did you check all the fuses and look for fusable links ?

 

[fastback]

Unclear as to if you are still using the external jumper. Are you sure the battery is any good? With an alternator type system (automotive) an engine wil not run unless the battery will hold a charge. A non-charging system will not affect the spark unless you have no source of voltage. As already suggested by BK check for a fusable link and or fuses. These are only suggestions since I am not all that familiar with these systems.