Vacuum Hub Question
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Junior User
Joined: May 2010
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Vacuum Hub Question
Tried using 4x4 other day and noticed front wheels weren't engaged in Auto mode. Switched to Manual mode and all O.K.
Question is . . . What should the vacuum pump pull for readings. Mine shuts off at 14 inches. Canister is at 14 inches and will stay there for hours. Solenoid going to hubs shows 7 inches when going into 4x4 for around 45 secs and 7 inches for 25 secs when switching out of 4x4. I thought there needed to be like 15 inches of vacuum to engage from what I've read on the forum here?
Is my pump bad? Should there be more vacuum there?
Question is . . . What should the vacuum pump pull for readings. Mine shuts off at 14 inches. Canister is at 14 inches and will stay there for hours. Solenoid going to hubs shows 7 inches when going into 4x4 for around 45 secs and 7 inches for 25 secs when switching out of 4x4. I thought there needed to be like 15 inches of vacuum to engage from what I've read on the forum here?
Is my pump bad? Should there be more vacuum there?
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
14 inches is good at the pump, canister and solenoid inputs. You should get the full 14 inches at the solenoid output for lock, and the 7 for unlock.
You may have a bad solenoid, or corroded wires at the connector. The center wire of the connector should be hot in Run. One of the outer wires grounds to activate the solenoid for one cycle (lock or unlock) and both wires are grounded to activate the solenoid for the other cycle. Unfortunately, I forget which wires for which cycle and whether it's one for lock and both for unlock, or vice versa.
It's in a thread around here somewhere, I can search for it later.
You may have a bad solenoid, or corroded wires at the connector. The center wire of the connector should be hot in Run. One of the outer wires grounds to activate the solenoid for one cycle (lock or unlock) and both wires are grounded to activate the solenoid for the other cycle. Unfortunately, I forget which wires for which cycle and whether it's one for lock and both for unlock, or vice versa.
It's in a thread around here somewhere, I can search for it later.
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
Here is the thread I was referring to. It describes which wire does what going to the vacuum solenoid.
https://www.ford-trucks.com/forums/9...ml#post9180620
https://www.ford-trucks.com/forums/9...ml#post9180620
