Hey guys,
On my 09 powerstroke my auto 4x4 won't engage. If I get out and lock the manual hubs it engages fine. The dash lights change when I flip the switch and the front driveshaft locks in but not the hubs. Any clue what could be causing this?

 

Have you tested the vacuum pressure at each of the front wheels? I have heard there is a quick test to see if you have a leak in your vacuum system for the 4x4 by turning your air on the vents and switch to 4H or 4L on the ESOF switch. If you have a leak in the 4x4 vacuum system the front vents will switch off and it will be redirected to the defrost vents.

 

I'll give that a try and see what happens.

 

If it turns out that you do have a leak in the 4x4 vacuum system it will more than likely be the rubber tubbing running from the 4x4 vacuum solenoid to each of the front wheels. If you don't have a leak in the 4x4 vacuum system then it probably is the 4x4 vacuum solenoid itself.

 

Do you know where the vacuum solenoid is on this truck?

 

Found the solenoid. Is there anyway to test the solenoid? The vents didn't change, so I don't think it's a leak. I have a vacuum gauge just not sure how much vacuum it should be pulling.

 

I have a 2003 F250 SD 6.0 diesel and mine is located on the passenger side towards the firewall. The vacuum accumulator tank is located in the same area and so is the 4x4 vacuum solenoid. I don't know if they are located in the same area on your 2009 or not but I can hear my vacuum pump run when I turn my key to the Run position without starting the engine. It should run and build up a vacuum pressure then turn off. It will run again once the vacuum pressure falls to a certain level and pump again until the vacuum pressure shutoff is reached again. This is only on the diesel model trucks. The gas models get their vacuum from the engine.

 

If you have a vacuum gauge I would disconnect the output vacuum line (the side that goes down to the front wheels) and connect my vacuum gauge to the output side of the solenoid, switch the ESOF switch to 4H and see if you get a vacuum reading on the output side. It's not a lot of vacuum pressure needed but you can disconnect the input side of the solenoid and measure what your pump is producing going into the solenoid and you should get the same amount of pressure on the output of the solenoid when the ESOF switch is in either 4H or 4L position.

 

The wiring going to the solenoid, is it a three wire connector?

 

First you need to check to make sure your vacuum pump itself can create more then I think it was 11 inhg of vacuum. You can check this by unplugging the vacuum line connector at the pvh solenoid and hooking vacuum gauge to the line that runs to the pump...turn on ignition and wait till vacuum pump stops.

Next thing you'll want to test is that the pvh solenoid is sending the right signals. You'll want to reconnect the vacuum line from the vacuum pump to the correct port on the pvh solenoid.....and hook the other port of the pvh solenoid to your vacuum gauge. Just twist the double port vacuum connector at the pvh solenoid to achieve this. Once again turn on ignition and wait till vacuum pump stops. Now with ignition still on turn the 4x4 selector **** to 4x4 high. Go and look at your vacuum gauge.....it should read about i think it was 10.5 inhg or slightly higher of vacuum for 20 seconds or so. (This is the signal that causes hubs to lock) After the 20 or so seconds are up the vacuum is vented to atmosphere. Wait a minute or two and then go turn the 4x4 selector **** back to 2wd position. Go back to your vacuum gauge and it should read between 5-7 inhg of vacuum for I think 10 plus seconds or so(this is the signal that causes the hubs to unlock) and then once again it'll vent to atmosphere. If both of these tests pass then your pvh solenoid is working properly.

Next step test the vacuum line from the pvh solenoid to the hubs. You'll want to go to each wheel and pull the vacuum line off of the steering knuckle nipple and plug them. Go back to that double vacuum line connector at the pvh solenoid (make sure you get the line that goes to the hubs and not to the vacuum pump) hook your vacuum gauge/pump up to this line and pump it up to say 15 inhg of vacuum or so......if it holds this for a few minutes...then the lines from the pvh solenoid to the hubs are good.

Now the last and most fun step....seeing if the hubs hold vacuum. Since you already have the vacuum lines disconnected from the nipples on the steering knuckle, hook your vacuum gauge/pump to each side and pump it up to 15 inhg of vacuum and see if it holds for several minutes. If it holds the vacuum then the hub and knuckle seals are good. If it does not hold the vacuum then either the hub seal or the knuckle seal is bad. Now determining which one of these seals is bad is the fun part. If one side of the truck tests and holds vacuum then you know for sure that the hub and knuckle seals are good. Take the good hub off of the side that holds vacuum and put it on the side that does not hold vacuum. Now retest this side......if the vacuum still does not hold then you're pretty sure that your knuckle seal is shot( remember the hub seal held vacuum on the other side)...You can also take that hub from the side that didn't hold the vacuum and put it on the side that did hold.....if the side that previously held vacuum now does not....then that hub and or seal is bad.

Hope this isn't to confusing lol.....This is all going from memory..so my numbers may be slightly off...but should do what you need to do.