I don't have a ranger yet but I am looking at getting a 2003 or so. I don't nesisarily want to add remote start, just a way to start the car and leave it run in with the doors locked and not take the risk of someone breaking the window and driving offwith it cause the key was in. So I was thinking would it be possible to add just a hidden swicth / button to only start the car with out a key in it and not apply accessory power, or any way of it being able to be driven off in that state . Then when I need to drive put the key in and turn it to accessory. Would that be possible? I was also thinking would it work adding a sensor to just shut the engine off if it was put in gear, unless the key was in and turned to accessory

 

Welcome to the forum

No, no way to do that, as you described, but may be a work around

Why it's no without a key
Rangers got PATS in the late 1990's, Passive Anti-Theft System - PATS
This requires the correct PATS key to be used in the key slot, or fuel pump and fuel injectors will not work, in some models no starter motor either
Each PATS key has a unique ID number, and that number was programmed into the computers memory at the factory, new vehicle would have come with 3 PATS keys each added to memory, and Ford dealers or most lock smiths can make and add PATS keys to the computers memory as needed.

So a working PATS key would need to be in the ignition to start the truck, once engine starts PATS is no longer used, so if key slot was worn out you could pull out the key, lol, and then lock the truck.

If Ranger is an automatic you have to press down on the brake pedal to unlock the column shifter, brake pedal switch activates shift interlock solenoid, you could add a hidden switch that cuts off that 12volts to the solenoid, so shifter couldn't be taken out of Park until switch was turned "on"

And/or add a relay to that Brake power wire, so when brake pedal was pushed down relay would activate and cut power to ?? there are a few fuses in the cab fuse box that if powered off will stall a running engine

Fords remote start units use an "electronic" PATS key, it must be added to computers memory just like any other PATS key, but it's not a "key", just sends out the ID like a key would, ignition switch is left in OFF position/Steering Wheel Locked
This allows engine to be started remotely, but engine shuts off as soon as any door is unlocked, or opened, also if brake pedal or clutch is used engine shuts off, and steering wheel is still locked in any case, lol.
So vehicle can not be driven in "remote start" mode, i.e. if someone gets remote start fob without a key they can't drive the vehicle
These are also tied into engine temp and oil pressure circuits, and will shut off the engine if temp gets too high or oil pressure too low, they may also have a tie into fuel gauge, so would shut off engine if fuel level was too low.