4wd not engaging 1988 fj62

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RECRUISER

RECRUISER

10 Year
Joined
Dec 15, 2014
Threads
19
Messages
239
Location
Land Between the Lakes, Beautiful Western Kentucky
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Ok, I have read every post on this topic and I still can't get my 4wd to engage.


So here is what I have so far:
1. With Hubs unlocked with 4wd button pressed in (no green light by the way) engine running, driveshaft spins easily by hand. This is BOTH in 2wd high AND 4wd low.

On the firewall, the blue VSV solenoid has 12v power when the 4wd button is pressed and the RED VSV solenoid does NOT when pressed in. Then when I turn the 4wd button OFF this reverses, with the BLUE VSV having no power and the red VSV having power. But all this with no green light on the dash.

There is vacuum to this, it does "suck" when I put my thumb over the vacuum supply hose that is fed from the top of the intake manifold.

I bought a new Blue VSV vacuum solenoid from the dealership part # 88690-89132 and installed it (easy job) and still no change.

Hope to hear back as It is an incredibly nice truck.
 
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If your 4WD Lo manual shifter(and linkages) doesn't engage 4WD then the problem is not in the VSV's or the hubs.

php74 is probably asking you to confirm that with hubs locked you can't turn the driveshaft. If you can't that at least confirms the hubs are working.
 
php74 said:
So with hubs locked, 4wd button pressed what does it do? Front shaft still turn by hand?
Click to expand...

With hubs locked, the drive shaft does not spin in any configuration. Of course this is with the front wheels on the ground. But still that tells us that the front hub/& wheels are engaging with the front drive shaft. Now we just need to get the transfer case to engage! Thanks for the question and I don't know where you're going with that question but if you have an idea, I'm all ears.
 
Randy88FJ62 said:
If your 4WD Lo manual shifter(and linkages) doesn't engage 4WD then the problem is not in the VSV's or the hubs.

php74 is probably asking you to confirm that with hubs locked you can't turn the driveshaft. If you can't that at least confirms the hubs are working.
Click to expand...
Yes hubs seem fine, and when the lever is shifted to 4wd LO, it does change the gear ratio properly and the truck crawls along in low properly and is strong, but without the benefit of 4wd.
 
I would test your transfer control relay next.

After that I would be looking at the diaphragm.

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I am quoting Randy88FJ62 who posted this on the "Writeup: 1988 FJ62 4WD Solenoid fix for $17.77" thread. I just want to thank Randy and tie this response in since it's regarding the same issue for whoever comes after us and benefits from Randy's work and efforts.

"Hi recruiser,
You do not need the front hubs locked to check the driveshaft locking with the tcase. The driveshaft locks when the VSV tells the vacuum diaphragm bolted on the end of your tcase to actuate.

Here's where I would start and work my way down:
1. Put eBrake on and foot on brake, put transmission into neutral. Then shift the 4WD shifter from 2H to 4Lo. Put truck back into park and check that the front driveshaft is locked. This will tell you if your tcase is working manually.

2. Take it out of 4Lo and back into 2Hi. Now we need to test the 4Hi.
-pop the 4H button bracket off and verify the 4Hi switch is connected. Test with a multimeter to verify it's getting power. If it is and the light isn't turning on then it could be a bad bulb or the sensor on your tcase could be unplugged, bad wires, or defective.

3. Now that you verified the switch is working, push it down and go check the driveshaft. If no good then we move to the VSV's on the firewall.

4. Your situation is odd. The Red VSV usually fails casuing 4WD to be engaged rather than your issue of not engaging.
-Get under the truck and visually make sure the two vacuum hoses are going into the diaphragm. If they are not then the VSV's won't be able to tell the tcase to switch via air power.

4. If the diaphragm hoses are connected then swap the hoses on the VSV's. This will test to see if the blue VSV can do the job for the red VSV.

5. If this doesn't work then try blowing on it yourself. If this doesn't work then it's factory service manual time. Donwload it on here or buy a paper copy. "
 
This question is for Randy88fj62.
I did a search on the transfer control relay and could not find any reference to what it looked like or where it was located on the truck. This would be a great piece of information to have posted in this thread as I'm sure someone else will go through this troubleshooting process and need a roadmap.
Thanks! I very much value your input.
 
I don't know where it is. I'm checking the FSM but they don't always list locations which can be a pain. As shown above is is a 4 pin connector and circular in shape.
 
Looking through the FSM and then recalling my truck I would check for it in these locations. They are usually labelled so read em as you go before pulling all of them.

1. left knee when driving behind fuses. Lay your head where your brake pedal is. There are a bunch behind the fuse panel.

2. Passenger door kick panel (left foot). Behind panel there are a few relays. There is for sure a circuit opening relay there which is unrelated to your issues.

3. On the tcase somewhere or near the VSV's on passenger firewall?
 
LOL love an honest answer.
I am actually well acquainted with that open circuit relay by the passenger right foot! That little relay all by itself kept my fuel pump from running, but I digress.
I will start a search for that little sucker and we'll post location and pictures.
 
Transfer L4 position switch would be checked after the relay. If the relay and the VSV's on the firewall all work then the last two items are the L4 position switch on the tcase and the diaphragm itself. Have fun...
 
Found the probable location of the relay, above the brake pedal there is a cluster of silver round relays.
Now I'm just going to crawl some part numbers and see what kind of names pop up for them to locate proper relay.
 
Cruiser Parts.net says that part #
90987-03001 is the "front drive relay."
It is round and silver and is located above the brake pedal.
Continuity is supposed to be between pin 1 & pin #2.
I get a reading of .063 between those. That is close to zero, pass?
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Also:
I have 12.15 volts to the 4wd switch on the dash but only 11.63 volts at the relay.
I'm thinking that may not be enough power to operate the relay?
 
I actually tested the relay per FSM and and then reinstalled it and listen for the click when I engage and it did click so the relay appears to be fine even though there's only 11.8 volts to that relay, it is operating fine.
Now to go the next step down the line.
 
This indicates that everything with the button is working fine. Start the engine, double check vacuum(should be on one line to each VSV) to the VSV, then check each VSV line going TO the Tcase. One should have vacuum, and the other when the button is pressed. If this is true then you have an issue with the lines or actuator.

Check to make sure you have a good ground at each VSV plug. It's the wire at each VSV that is the same color/strip combo.

Forget about the 4wd relay right now.

Also for a quick check, take one line going to the actuator and hook it to the line going to the manifold vacuum. Spin the shaft, does it lock? If not hook the other to vacuum. If that doesn't lock look more into the actuator or lines going to it.

RECRUISER said:
On the firewall, the blue VSV solenoid has 12v power when the 4wd button is pressed and the RED VSV solenoid does NOT when pressed in. Then when I turn the 4wd button OFF this reverses, with the BLUE VSV having no power and the red VSV having power. But all this with no green light on the dash.
Click to expand...
 
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