My front wheels wont engage when I select 4H or 4L. No dash lights are ever lit.

I read up and understand how the system works and plan to replace the solenoid, transfer case motor and both hub actuators. I swapped out the solenoid and wanted to test that it was functioning properly so I followed the video below:


With the engine running and selector switch at 2WD, I pull the vacuum lines off and can feel vacuum at the supply. I then hook up just the supply line up (to the bottom port) and expect to feel vacuum at the other solenoid port (top port - what I would call the outlet) and cannot feel any vacuum.

This has halted my repair attempts as I am not convinced this is functioning and would pull in the actuators if they were functional. I know it's a small vacuum from a small orifice but I would think I should feel it by hand, no?

The solenoid's electrical connector is plugged in during this as well.

I get the same performance with the old solenoid and the new.

If I bypass the solenoid I can feel vacuum at the front wheel hubs.

I have done a lot of reading on forums and cannot seem to find anyone expressing this same concern. Should I try a third solenoid? Seems unlikely I would have 2 bad ones...

No OBDII codes at all

Any ideas on what to try next?

 

you need a vacuum gauge, not a FEEL.

 

Just confirmed with gauge that no vacuum is leaving the solenoid. 20 inhg coming in. And that is on both solenoids.

also just replaced the transfer case motor, still no lights on the dash when switching between 2wd and 4wd.

 

I know it doesn't explain the lack of vacuum issue on the solenoid, but perhaps there is an electrical issue? Why wouldn't I be getting dash lights? Brand new transfer case motor...

 

What if you unplug the solenoid connector and provide 12v and a ground to the solenoid? Will it then pass a vacuum?

 

I can do that in the am. No more daylight right now.

would it be easier to measure the connector with the engine running? I'm not sure how I could jury rig a 12v setup and test the vacuum without shocking myself

is the solenoid polarity sensitive? Don't wanna flip it and blow it...

 

Don't forget to check for a blown fuse.

 

Any particular ones I need to watch out for? Everything at the passenger footwell fuse box looks ok.

 

I had one come through the shop a while back with solenoid problems. The solenoid was on one of the air conditioning fuses. Something was shorted on the ac system and blowing the fuse . I don't remember what fuse it was.

 

put a dmm across the two pins of the solenoid connector and got 12V. i think that would rule out a fuse, right?

i guess i have 2 faulty iwe solenoids? seems crazy...

anyone?

 

the video I posted shows an unenergized solenoid passing vacuum through the 2 ports. I cannot do that on the original or the replacement solenoid. Am I misinterpreting that?

 

I though when you started the truck it powered the solenoids and passed vacuum to pull the IWE OUT OF 4 x 4............. so with no power, you should have no vacuum ?
did you check the solenoids WITH power ?

 

from the IWE sticky post at top of this forum--------

If when you try to shift into 4WD and it will not engage, most likely your solenoid is not working and releasing the vacuum to the actuators and engaging the hubs. Replace the solenoid. This might happen because of the early design of the IWE solenoid with lets water run off the cowl right down on top of the solenoid possible shorting it out. The new style solenoids have a rain cover on them to prevent this. This is all being said as long as you know your shift motor on the side of the tranfer case is working properly.

-If your in 4WD and it will not shift out, the solenoid is not opening back up to let vacuum release the actuators. Replace the solenoid. Again if the shift motor is working.

-If you hear a grinding or whining of gears at certain speeds or loads you probably have leak in your vacuum system somewhere and your vaccum is dropping to or below the 5 lbs of vacuum needed to keep the actuators unlocked. Check the following:

 

I read that as:

2wd on switch - vacuum at iwe actuators

4wd on switch - no vacuum at the iwe actuators.

this is not what my brand new solenoid is doing.

 

I think that is correct....... BUT , I though when you shut the truck off and vacuum goes away ( and solenoids have no power) , that the IWE engaged the 4 x 4......... So , no elect power = no vacuum = 4 x 4 engaged ??

from IWE sticky note--------

When the system is working correctly, vacuum is placed on the system unlocking the hubs while the truck is running. When shifting to 4WD vacuum is relaesed, locking in the hubs. A vacuum leak at any part of the system can cause failure.

When the engine is started and running, vacuum is exerted on the entire system, unlocking the IWE actuators. When the engine is turned off or 4WD is engaged (either by floor shifter of dial selector) vacuum is released by the IWE solenoid to the actuators at the wheels. So vacuum to the actuators at the wheel unlocks the hubs for 2WD and release of vacuum by the solenoid locks them for 4WD.