i have a 1992 blazer with push button 4 wheel drive and when you push the button the 4 wheel drive won't work no lights no nothing, but when you first start it up the lights on the button flash

 

Same problem on my 93.Will let you know what I come up with today

 

i think there is a vacum line which engages the 4x4. i had a friend with an 80's s10 and he had the same problem. he looked underthe truck and saw a line dangling, hooked it back up and he had 4 wheel drive again. i couldn't tell you where it is though, 'cause i don't have one.

 

just in case you didnt know i dont know if you have put it in 4x4 before so... you have to be in neutral and moving at 3-4 mph to put it in 4 lo again i dont know if you were trying to put it in 4hi or 4 lo as for 4hi i forget if you have to have it in neutral or not...if youhave an owners manual for it you should check it out see what it says...i dont know how much help i have been but good luck

 

on my blazer, it has a vacuum controlled switch that engages the 4 wheel drive and turns on the 4 wheel light when engaged, those vacuum hoses, because of the angle that they are at, tend to swell, or break or just slip off, look by your transmission linkage for vacuum hoses half way on, broken or just completely missing, its a hard place to get to so it is better to use ramps or a lift and a good flashlight. if no apparent problems stick out to you, try using dishsoap mixed with some water and coat the hoses with it, start the vehicle and try to engage the 4 wheel drive, see if there are bubbles or hissing, noises.