When I purchased the truck the ESOF system didn't work as intended. In winter I have been simply locking my hubs and then using the switch in the cab and it will engage or disengage my 4wd high and low properly.

Heater works fine, A/C works fine... But my truck seems to want to stall when I am coming to a stop when I am in 4wd. So I must have a leak somewhere...

I have replaced both front hubs and new locking hubs with seals. I replaced the threaded fitting into the knuckle as both of mine were rusted out. I put in new lines from the knuckles to the elbow adapters going upwards into the engine bay. I NEVER hear the vacuum pump running, but like I said ESOF works if I lock my manual hubs and use the switch...

It looks like I have a spaghetti of wires, the left hub knuckle and the right hub knuckle look like they both have hoses that T into another hose. That hose then goes up into the engine bay to what looks like a Vacuum solenoid? It's winter here and hard to tell.

Basically looking for some guidance as I don't own a smoke machine to test the vacuum hoses. I do own a vacuum guage, but since I never hear the vacuum pump run is it safe to say the pump is either dead or not getting power? I didn't know if my particular truck used engine vacuum instead of a pump.

Where would the vacuum pump be located? Sorry for all the questions. I have rebuilt many engines and done plenty of other mechanic work in my life, but I have never dealt with 4x4 systems.

My other question...

Is there a way I can just delete the vacuum crap and just manually lock/unlock my hubs like I am currently doing to eliminate the vacuum leak? Will this affect the switch in the cab that engages the driveshaft to the front diff? (I assume its electrical and wouldn't affect it.)

Visually it looks like the spaghetti of wires goes into an EVAP purge solenoid, a vacuum solenoid and some big canister that's kind of oval looking.

 

I tested this connector with Key On Engine OFF and I get 11.43 volts. You can see the big oval canister I was referring to in my previous post, just right of where my hand is, with all the vacuum lines above it.

 

Ok, I used compressed air and soapy water and couldn't find any leaks in the lines... I disconnected the two lines that come from that solenoid in the picture and since the connector had 12v, I would assume that is some type of pump that fills that low pressure reservoir (The blank oval thing)? I didn't hear or feel any suction or blowing on that device. So my guess is that device is broken. It looks like one line goes to the reservoir and the other line off that solenoid goes to my hubs. That device with the 11.4v looks much like a EGR vacuum regulator solenoid.. Which is odd because my truck doesn't have an EGR system hooked into the exhaust.

No leak in the EVAP/EVAP line or the lines that go to the side of the throttle body/intake area.


Ok, after talking to parts store... The device that sits on the passenger side that I tested is getting 11.43v is the Pulse Vacuum Solenoid or PVH.

 

if your heater and ac controls work properly, my bet is that the auto hubs themselves may be bad. if the heater controls still work the way they should when ESOF is put in 4 wheel, than i would just use the current hubs and lock them when you want 4 wheel drive.
if the heater does not work properly, then swap the auto hubs for a set of warn premiums.

 

Ok, I found a diagram and this is what looks like what happens to engage your front tires to lock.

Switch inside turned from 2wd to 4wd.

1. Transfer case is electronically engaged
2. GEM module sends a ground signal to one side of the PVH to tell the hubs to lock.
3. PVH initiates about 15Hg vacuum to lock your auto hubs.

When you switch from 4wd to 2wd

1. Transfer case is disengaged
2. GEM Module sends a ground signal to the other side of the PVH to tell the hubs to unlock.
3. PVH initiates about 6Hg of vacuum to disengage hubs.

This is simplified, but hopefully helps.

From my understanding if I can not find a leak in my vacuum lines themselves then the next logical device to look at is your PVH as that is what initiates the process... Doubtful your GEM module is not sending a ground signal and the cause of the issue.

The heater explanations as follows makes sense...

Switch from 2wd to 4wd using the switch and your heater controls act like they are changing makes total sense as you do not have enough vacuum to hold the louvers. IE: heater controls are set to face, but when you turn from 2wd to 4wd the air starts blowing from the defrost vents. This would indicate a vacuum leak in the lines or hubs.

Since my heater controls work just fine I highly doubt I am having vacuum leak issue.

Also, Diesels are the only Super Duty vehicles equipped with a stand alone vacuum pump. This is due to the fact that diesels do not produce enough vacuum to utilize the vacuum lines from the engine.

I think I found my issue, just had to think it out. I will measure vacuum from the PVH side that goes down to my hubs by using a minivac and see if I can engage/disengage my hubs to be sure my lines are ok from that side of the PVH system.

 

sounds like a logical plan since the heater controls work properly.
unfortunately i have absolutely no knowledge at all about ESOF except for the fact i have never worked on or owned one until today when i bought the loaded 2014 truck.

 

I work at Federal Mogul, and we introduced a hand installable seal for the late model F super-duty series of trucks, now we have a new offering for 05-09 F super-duty truck. I am looking for volunteers in Chicagoland to replace your front seals and install our latest offering.

Interested?

email David.Rupp@federalmogul.com or call me at (847) 568-2195