99 & up 7.3L Power Stroke Engine and DrivetrainDiscussion of the 99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.
The auto hubs work on a vacuum pulse. This seems not to be working in your truck.
First check the vacuum system. This fairly easy. If your heater is not stuck on defrost, your vacuum system is working.
Next check the vacuum hoses to the hubs. They run from the fender area to the hub.
If all is good up til now, you need to check the vacuum relay on the passenger side fender (engine compartment). It has 2 vacuum hoses and a plug with 3 wires. Make sure the plug is plugged. I don't have a simple test for this relay.
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2011 f250 XLT 4X4 Crew Cab.
SOLD - 2001 F250 XLT 7.3L SC/SB 4x4 (ESOF) - Tranny Upgrades; SCMT 1705; AIS Intake w/trimmed Snorkel; ZooDad; Turbo back 4" Exhaust; Issopro Pillar Mount Gauges; TC lockup LED; Auto Magic Heater Bypass; 2W Low Switch.
It's an electric pump located on the passenger side wheel well. The easy way to test it is to raise the hood, turn the switch on (don't start the truck), and listen for the vacuum pump to run and then shut off. If it doesn't run, check the fuses first. If it doesn't turn off, you have a vacuum leak. Check this first and then we can go from there.
Joe
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2002 F350, Crew Cab, 4WD, ISSOPRO Gauges,
3.73, Auto, 2wd low range mod, No door dinger,
Interior lights off switch, Zoodad Mod,
Extra Trans Cooler, Before coolers trans fltr,
Coolant fltr, Crimestopper remote start/alarm
Oil Guard Bypass, Air horns
It may be just the connection at the back of the hubs. Sometimes these pop off or get cut, just cut an inch off and stick them back on. Good luck, and yes the locked position is your back up when the ESOF system fails.
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NCH
2000 Ford F350 4X4 Auto,Crew Cab Lariat, Western Hauler Package, Long bed,
Isspro EV Guages on A-Pillar, Coolant change from Green to Gold to Red,
SCT XCalibrator2 with DP's 60 tow,80 econo,120 Race
Fumoto Valve, Marinco Mod, Homemade CCV MOD,Fuel Neck Mod, KMC Wheels at all 4's
Monroe Reflex Shoxs, SS/Kevlar Brake Lines,
FTVB from Greg Evans,Ford AIS Intake
Coolant filter,Walker BTM, Attwood Gooseneck ball flush mount,6.0 cooler, 2002 headlights & corners
Zoodad Mod,Cyro'd Powerslots and Hawks LTS Pads. 2005 front grill
Turbo Lifesaver, Infinity Refrence x4, powered by Infinity Reference amp, sounds awesome!!
Towing a 2005 HORNET 30BHSS 8500 LBS,
Stopping it with a Prodigy P3 Controller
Friends Don't Let Friends Drive Trucks With Generic Tunes!!
I fought the same problem. I replaced the fuse. I think it was 29 a 15 amp fuse on the right side of the fuse box about halfway down. The fuse would blow quite often. The last time I went to replace the fuse, the fuse was fine. I ended up with a new vacuume pump. I could only find it at the dealer and it cost about $145. I swapped out the pump and things worked fine. A day or so later I had the hood open for another reason and I noticed the vacume pump kicked on. I noticed that after about 3 or 4 seconds it stopped. 3 or four seconds later it started again. It continued to repeat this cycle. I finally traced it to a bad sylinoid. The one on the fender wal with the 3 wire plug.
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Early 99(4-98,) F-350 CC shortbox Lariat, 285/75/R16, In-tank and pre-pump mods, EDGE Juice W Attitude, EDGE Evolution. AIS Intake, Zoodad. 210K miles.
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It may be just the connection at the back of the hubs. Sometimes these pop off or get cut, just cut an inch off and stick them back on. Good luck, and yes the locked position is your back up when the ESOF system fails.
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Sorry Kevin, if a connection at the hubs is leaking, the system will only show fault while it is trying to engage the hubs. In other words, it will go into defrost for a short period of time and then appear normal again. The hubs work on a vacuum pulse and not a constant vacuum.
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2011 f250 XLT 4X4 Crew Cab.
SOLD - 2001 F250 XLT 7.3L SC/SB 4x4 (ESOF) - Tranny Upgrades; SCMT 1705; AIS Intake w/trimmed Snorkel; ZooDad; Turbo back 4" Exhaust; Issopro Pillar Mount Gauges; TC lockup LED; Auto Magic Heater Bypass; 2W Low Switch.
By the way. I tested the pump it was also bad. My best guess on what happened was that the leak caused the pump to cycle. After several months or longer of continuous cycling, the pump started to go. As it went out it started drawing more current which is why i was changing the fuse so often. Finall the pump went out completely and stoped drawing current. Thats why the fuse was good the last time I checked it.
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Early 99(4-98,) F-350 CC shortbox Lariat, 285/75/R16, In-tank and pre-pump mods, EDGE Juice W Attitude, EDGE Evolution. AIS Intake, Zoodad. 210K miles.
well, i manually locked my hubs and went out plowing for about 8 hours and the truck died...i put in a new alternator and everything works perfectly now!
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