My 1995 Blazer will not engage in 4x4. It is a 3 button system. I cannot read the codes with my OBD II code reader, I was told in another thread that 95 was a crossover year and it's OBD "1.5". With the engine off and ignition on, pushing the 4x High button will give me a satisfying "clunk" in the transfer case.

With the battery and tray removed, the vacuum actuator looks fine, no cracks or tears, it is pliable and appears intact. With the engine running and my wife pushing the 4x High button for me, the actuator does not pull the cable. With my hand on the diaphragm I can feel it contract, but only slightly.

My mechanic says it runs like it has a vacuum leak somewhere. Would this effect the pressure on the actuator? He couldn't find one, and I don't even know where to start looking for that. I don't have a gage to measure vacuum pressure. Is there a common place these 4.3s developed vacuum leaks?

Should I just do the locking pull cable fix?

Thanks. I know some of you are surely tired of answering what seem to be common questions to you, but the DIY OBDII thread is no help since I can't read the codes, and I don't believe the diaphragm is suspect.

Also, I'll add it runs poorly when in low idle, lopes at high speed, and sucks about 11 mpg when at one time I got 18mpg out of it, if that gives any help to the vacuum leak idea. Check engine light is on.

 

You do not use a reader to read the TCCM codes unless you have the Auto4wd NV236 transfer case. You have the NV233 transfer case as such you should be able to do the paper clip trick on the DLC using either the information in the OBD2 Non-Automatic Transfer Case Diagnostics for the OBD2 DLC or THIS THREAD for the OBD1 DLC.

As far as common locations for vacuum leaks... There really is not a common location. With a 13 year old vehicle, lines could be rotted and cracked just about anywhere. The only fool proof way to eliminate any and all vacuum leaks is to replace the lines. It may not be a vacuum leak persay, but could be a collapsed line due to age. Collapsed lines are very difficult to diagnose as you may not see any problem with them.