Remind me ... the banjo bolt your talking about, where is it in the fuel flow? (After lift pump/before solenoid/injector pump?) A solenoid that doesn't let fuel into injector pump could give you lots of fuel before the Injector pump because you are simply pumping from the tank & back to the tank via a slightly smaller return line, which creates pressure. What you want is to see if fuel is entering the injector pump and coming out of the injector pump. Have you jumped the solenoid while it's on the tractor to make sure it opens & let's fuel flow into the injector pump? My Zero turn had a jumper switch installed when I bought it since the previous owner didn't want to diagnose the loss of power problem to the fuel solenoid. This could still be a bad solenoid or wiring/relay problem.