1991 LJ not shifting out of 4wd (1 Viewer)

[Canarias]

Hi. Spanish 1991 LJ73 manual with 2L-Tii. This is the 1991 onward model of the LJ7x.
Shifting from hi to low is mechanical but the same shifter activates relay/solenoid/vacuum to shift between 2wd and 4wd.
There is also a 4WD button on the dash to toggle 4hi and 2hi

Solenoids are pictured.
Blue solenoid controls vacuum to shift to 4wd
Brown solenoid controls vacuum to shift to 2wd
Shifting from 2 to 4 works.
Shifting from 4 to 2 doesn"t work. Neither with dash switch nor shift lever.

I can workaround successfully in 2 ways
i) apply 12V directly to the brown solenoid
ii) swap vacuum lines between blue and brown solenoid and shift into 4wd, which puts me in 2wd
So it seems solenoids, vacuum and mechanicals of tcase are good. Hence suspect electrical/wiring problems.

Does anyone have a wiring diagram or any other helpful suggestions please?

I have freewheeling hubs so this isn't killing me, but i want this to work so I can put the vehicle up for sale.

 

[GTSSportCoupe]

I had the same problem and it turned out to be one of those vacuum switching solenoids. They burn out over time. I snagged another similar one from the wreckers from an emissions system on a random Toyota and it works fine.

 

[Canarias]

I had the same problem and it turned out to be one of those vacuum switching solenoids. They burn out over time. I snagged another similar one from the wreckers from an emissions system on a random Toyota and it works fine.

Solenoid seems to work because if i give it 12v via leads from battery then it shifts.

 

[GTSSportCoupe]

Sorry, I missed reading that in your first post. Maybe check the resistance of each solenoid coil to make sure they are both the same. One of them could be partially shorted internally so that it works from a battery but not from the 4wd computer.

There are wiring diagrams for these on this site. RM183E is the right manual for your truck I believe.

 

[Canarias]

Thanks, have downloaded manual. Will get some laptop time this aftnoon and have a look. My LJ has the mechanical injection and no ecu. Does it have a 4wd computer or is it done by relays. Multimeter shows a momentary blip on each solenoids connector as the shifter moves in and out of 4 with engine off. I was expecting a persistent signal until the 4wd position sensor confirmed the move and closed/opened a relay.

 

[Canarias]

According to the wiring diagram, as well as the two solenoids I've described and pictured above, there is a third solenoid called VSV (transfer case). I dont know what VSV stands for but in the manual its named in french as "soupape de commutation a depression" which means valve to cut vacuum. What does this do? The other solenoids are described as vacuum switches so I'm guessing the VSV is different in some way.

 

[roscoFJ73]

Normally on a Toyota VSV = vacuum solenoid valve, which is what I got on google translate when I put in "soupape de commutation à dépression"

But unless yours is different I've always known the vacuum shifter as the " DIAPHRAGM CYLINDER & TRANSFER VACUUM ACTUATOR " on the T/Case, which is what the EPC calls it.
This is the bit Im talking about. Do you have a pic of this VSV?

 

[Canarias]

Hi Rosco. Yes i have the diaphragm cylinder actuator. The diaphragm shifts between 2 and 4 when vacuum is applied to one or other of the two vacuum lines to it. That all works as i can fudge it by putting the 2wd line where the 4wd one should go, or by putting 12v direct to the 2wd solenoid. Seems to be just the wiring or switches, or maybe a solenoid kinda working but not properly. The 2wd and 4wd solenoids are pictured above. I have found the location in the manual of this other vsv and will spend a bit of time with the vehicle and a voltmeter later today. Right now I'm suspecting the 4wd position sensing switch.

 

[roscoFJ73]

I have found the location in the manual of this other vsv

Where is it?

Have you checked the 4wd switch on the dash?

 

[clintnz]

@Canarias did you find a solution? I've been chasing this same issue on my LJ71. It seems to have recently gone from an intermittent fault to a permanent one. Both the solenoids check out ok, It shifts out of 4wd fine if I apply vacuum to the diaphragm manually. I need to check through what's getting power & when again.

There is a 4wd controller box under the dash, since I removed the electric hubs years ago it probably isn't doing too much useful any more, so maybe I could re-wire the whole thing with a couple of relays.

The 4wd light on my dash blew years ago so maybe I should try & fix that too so I can see what's going on without reaching under the truck to spin the front driveshaft.

Cheers
Clint

 

[GTSSportCoupe]

@Canarias did you find a solution? I've been chasing this same issue on my LJ71. It seems to have recently gone from an intermittent fault to a permanent one. Both the solenoids check out ok, It shifts out of 4wd fine if I apply vacuum to the diaphragm manually. I need to check through what's getting power & when again.

There is a 4wd controller box under the dash, since I removed the electric hubs years ago it probably isn't doing too much useful any more, so maybe I could re-wire the whole thing with a couple of relays.

The 4wd light on my dash blew years ago so maybe I should try & fix that too so I can see what's going on without reaching under the truck to spin the front driveshaft.

Cheers
Clint

Why don't you guys do this? LONG OVERDUE transfer vacuum valve conversion writeup

 

[clintnz]

Why don't you guys do this? LONG OVERDUE transfer vacuum valve conversion writeup

Thanks! I hadn't seen that before. I even have a 5 port pneumatic valve in the junk stash I think. Although I may just try a double pole switch connected direct to the vac solenoids first as I suspect the issue may be in the 4wd controller box.

Cheers
Clint