I just purchased a 743 that would not start. I had to put in new solenoid and rewire, all the way to the glow plugs. When that was done I rewired the started solenoid and put in the diode so when I turned the switch to left the glow plugs would activate, when the switch was turn to start the engine the glow plugs was also be activated durning the start up process. After the rewiring the Kubota starts like it was new. I would have some one turn the key to the left and check the power (blue/black wire going to small center bolt on solenoid ) going to glow plug solenoid and then check the power (white wire going to start solenoid center post and from that post there should be at wire with a diode going to the glow plug solenoid) when turn to the start position. If no power to these wires start chasing to connector behind seat. These solenoid a are to the left of starter under the air filter canister. Hope this helps I just went thorough this.