I have a 93 s-10 blazer the 4 wheel drive is not

There is three vacuum line on the driver side, top of the transfer case. One comes from the engine, 2nd line goes to the breather vent, 3rd goes to the 4x4 actuator diaphragm. The 4x4 actuator is located under the battery tray, check the vacuum line and listed for any vacuum leaks at the acuator. Inspect the cable from the actuator to the front differential (pumpkin), it's common for the cable clip on the pumpkin to corrode and will need to be replaced. Good luck and keep me posted.