My 4WD is not working in my 1984 s10 blazer. V6 2.8L engine. I have tried all kinds of things, unfortunately the vacuum system is beyond me. It seems as though when I shift into 4wd the lights will not come on and the 4wd will not engage. I have tried testing the vacuum suction at the 4wd vacuum switch, and have no suction. Perhaps if someone could point me to a vacuum diagram, or tell me why it looks like the vacuum for the 4wd goes through the firewall and into the cab, I could get this fixed. Thanks

 

i owned a 83 and a 85 s10 4x4 so i would think your 84 should be the same way. your vacuum actuator (i dont know the exact name of the part) should be on the fender. on your passenger fender under the hood you will see this little black bag looking thing with a wire coming out of it thats what engages your front axle. i got so sick of dealing with vacuum switches going out and just vacuum in general. on my 83, i just ran my own valve going to it so you just had to pull the lever to engage the transfercase then release the valve to send vacuum to the actuator on the fender.

on my 85 i said t heck with everything i manually squeezed it with my hand and put a pair of vise grips on it. drove that truck offroad for like 3 years like that never had any issues.