Engine Stubborn STT61-26DFI

[Knots]

Need help,
Have a Turf Tiger that is four years old with low hours that will not start. If you apply 12 volts to the small starter terminal it will start instantly and run all day. I have replaced the ignition switch, the pto switch and the relay. Checked all safety switches and they all trigger the relay. PTO function is normal and lights are OK. All fuses that I know about are fine. All replaced parts are OEM Scag. I have examined and wiggled all connections under the dash while having the key in the start position.
Anyone have any thoughts? I am stumped! Occasionally, when you try to start with the key, it will start and keep on starting for a few days then right back to no start.
Any and all suggestions would be greatly appreciated.

Thanks,
Knots a

 

[bertsmobile1]

Your problem is in the cranking circuit as you have already worked out.
You will need to work through it and it is a PIA to do.
Somewhere in the loop is a broken wire or bad switch or short to ground.
Scag use a complicated ( read expensive ) interlock module on some models
Scag put their wiring diagrams at the back of their parts books

I have found the easiest ( never is actually easy ) way to find the problem is by using small patch leads ( jumper with a spade at each end ) to bypass the switches one at a time.
Usually the power to the solenoid comes via the PTO switch.
The lap bars & parking brake provide a ground connection that causes the relay ( or module ) to connect the power from the PTO switch to the starter solenoid.

 

[Luffydog]

Check the ground by following the scag harness at the engine block make sure it's got good ground also to the battery to engine with a meter. Relay under key switch might be going out at times. Also check the fuse holder. There are 15 ways a scag won't start. Battery fuse relay pto safety and so on double check the ground. If all good pull the starter wire off the starter put something in the seat to hold switch and check with meter. Then do a test to check the wire to see if it is good