Hi all,

I have a 91 yota pickup that runs great. When I fixed up the truck a few years ago I had to hook up the vacuum lines to fix the 4x4, then it worked great for about a year. It has since died, no warning or symptoms... It just died. I have checked all the vacuum lines and everything looks good, but I cant get it working. What are some common problems that disable the 4x4?

I need ideas!!!

Many thanks!

 

There is this relay under the dash that says "fuel cut relay" on it. No joke, it is for the 4x4 system. Check to see if it is working. I'm sure you can find the procedures to test it somewhere on the net. If the relay works, then what I would do is put the front end on jacks, unplug the vacuum hoses and put a vacuum pressure in each one (it worked with my mouth for me) and have someone see if the differential locks. You should be seeing the drive shaft to the transfer case spin if it locks. If the first vacuum line doesn't work, try the other incase it was backwards. If you have any trouble here, you may have a mechanical issue in the auto hub area. Just open it up and clean it out.

 

Mine says "Horn Relay" on it. I guess they just grab whatever's on the shelf that day.

Gevo's advice is spot on.

 

I can hear the relay switch when I change the transfer case into 4x4.... So I don't think that's the issue. But I will still pull it and check then report back. Thanks for suggestions.

 

Are the relays in the engine compartment passenger fender clicking When putting into 4wd?


The hoses run through the fender wall to a vacuum holding tank then down to the diff.

 

No luck yet. I've checked all the hoses and they look good.

Regarding the 2 vacuum switches near the fuse box on the passenger side engine compartment.

When my transfer case is in 2 hi the red plug has 14V and the blue has 0V. When in 4x4 the red has 0v and blue has 0v.

Can anyone confirm this is problem? Thanks!

 

Also,

What is the ~4" vacuum hose on the top passenger side of the transmission/transfer case for?