I must have an electrical short somewhere. If I unplug the front PTO connector, forward of the running engine, the engine will die. The front PTO switch will not start the mower/PTO clutch. This 318 had a rear PTO, I removed it an put it on my JD430, along with the switch. I jumped the old plug, as indicated in the wiring diagram for a single PTO. The seat switch is bypassed. This 318 was a basket case when I bought it ($50) It ran great for one year, then I bought the JD430 diesel. I have not ran the 318 for two years/since I removed the the rear PTO unit and the rear PTO switch.
If anyone has had this problem, please chime in.
I know my way around with a digital multimeter. I will look for voltage, I will check one wire against another. I will check continuity with ground. I will let you know what I find. I also have the service manual.