1991 jeep cherokee jerks while in 4x4 on turns..

The best support site I have found for Dodge is here, Allpar Dodge Chrysler Plymouth Jeep and related cars minivans and trucks Look in the tech sections and you may find the answer or you can type in a question. Contrary to what one user posted, I have no affiliation with this website beyond having used it myself. Allpar Dodge Chrysler Plymouth Jeep and related cars minivans and trucks

Do you mean the switch or the key cylinder?

Turn the engine to TDC, so the line on the crankshaft balancer lines up with the zero. (Number one cylinder all the way up, and it should be blowing air with your finger in the spark plug hole on it's way up. This is TDC) Note, make sure you turn it the same direction as when it is running!!!! (Turn it with a socket on the end of the crankshaft, clockwise facing the front of the vehicle) Now with the distributor cap off, the rotor should be pointed at where the number one spark plug wire goes into the cap.

Ok, so the engine turns (cranks) when you turn the key to start?
Or, the engine turns slowly? Or, the relay clicks but the engine does not turn? I'm trying to help and you aren't giving me anything to work with!!! Tell me EXACTLY what is going on there...I can't see or hear it...you can.

ground the purple wire

your lucky you can drive in snow that deep.(in england traffic stops at the mere hint of the white stuff).seriously though the only answer is next time buy a 4x4 that is for off road use not a sand buggy.

Have you changed the trasmission fluid and filter in your jeep lately, if not do so and that just might stop the jerking in your jeep, and if that does not do the trick you will need to have your trasmission checked out by a trasmission shop.

check fuel system and see if you getting spark at plugs.

Sounds like the starter. If you remove the starter and take it to autozone or advance auto parts, they will test it for free.

you can test your signal wire to the starter by having someone turn the key to start while you put a test light on the signal wire at the stater.If there is no signal on the light then there is a problem with the sending wire from the ignition.