Will not run in 'ON' position

'90 Cherry, 2 dr, 4.0/ AX-15. Jeep was doing great with 213,000 on the clock, then out of nowhere, will not run in the on position. In the on position, everything works... radio, heater, blinkers, reverse light... exept it will not stay running. She starts just fine, runs normally until the key is released, then it's like the coil gets cut. Checked all my fuses, and the 4 relays under the hood, and they are all good.

Any ideas?

Ignition switch N/G.

Thought of that, but will that allow all the accessories to still work in the 'ON' position?

Hook the two leads to the ballast resistor together and give it a try. Ballast resistor is bypassed during start (fuel) and the fuel circuit goes through the resistor when in run. Jumping the ballast resistor won't hurt anyhting, it just cuts back on the voltage to pump during normal run.

drivers side of the engine compartment, just under the hood lip.

Alright, will try the ballast... that's the only thing that I think I have overlooked... hopefully...

Yup, was the ballast resistor, many thanks!