I'm working on a 1992 F-250 that won't start unless you turn on the parking lights. has anyone heard of doing this and where do I look for the wiring so I can remove it.

 

when you say won't start , does that mean it will crank but not run or does nothing when you attempt to start the engine.
The first thing you need to do is determine if power is being denied that is controlling either fuel or spark.
If the vehicle won't start because it is not getting fuel, go to the fuel system wiring.
If it is not getting spark, then you go to the ignition system wiring.
It sounds complicated, but once you know which system is being prevented from working you can confine your efforts to that system.

If you can hear the fuel pump run for the usual 2 seconds when you turn the key on , you have a pretty good idea the fuel system is not involved. NOT COMPLETELY !
If they decided to block power to the fuel injectors or the ECM power relay it will not start and is fuel related.and Ign related.
How about we do these checks before going into the ignition system.
This is just like any other no start problem except you know it will start with the parkinglights on.

 

I should have mentioned "It doesn't crank when you turn the key" Dash lights up and fuel pump runs but if you hold the ignition in START mode and turn on park lamps engine cranks.

With park lamps off and ignition in on position - if you jump the solenoid it starts right up.

 

If this vehicle is an automatic, one of the wires on the Manual lever position switch (Formally neutral safety sw) will have power to it in park and neutral position with the key in the start position. That wire should go to the starter relay on the fender well to energize the relay when the key is turned to start.

You can either try to locate that wire where it was severed and reconnect it or run a new wire from the MLPS to the relay small terminal.
If the person didn't get rid if that wire you might find it tucked in hidden among other wires close by so as not to be noticed.