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Unread 04-21-2012, 09:05 AM   #1
ymurf
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1979 CJ7 
 
Join Date: Apr 2011
Location: Steelville, Mo
Posts: 738
4.0 swap/VSS wiring

I put a 94 4.0 from a YJ in my 78 CJ7 with the AX15 and a Dana 300. I bought a 91 YJ Speed sensor and it has a two wire hook up.The wiring for the Speed sensor from the 94 4.0 has three wires. I bought the 3 to 2 wire conversion plug from Hesco..Which two out of the three do I hook up?

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Unread 04-21-2012, 10:16 AM   #2
1986cj
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1986 CJ7 
 
Join Date: Dec 2007
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I have copied this from cjoffroad, never tired it but guys say it works. The Early 2 wire VSS is a simple mechanical switch, it makes and breaks a set of contacts internally using magnets and a reed switch. One wire is from the PCM which has a 5 volt reference internally, the other is the sensor return. When the 5 volts drops to ground, the PCM senses a trigger.

The later 3 wire VSS uses a Hall effects switch to make and break the connection between the sensor return wire and the ground wire. The 3rd wire is a 5-8 volt power supply to operate the hall effect sensor.

The 3 wire sensor colors are usually:
Wt/Bk = 5-8v supply
Wt/Or = Sensor return (signal to PCM)
Bk/LB = Common sensor Ground

With the 2 wire sensors, just connect the 2 wires to the Bk/LB and Wt/Or wires from the harness, you can disregard the Wt/Bk = 5-8v supply wire, it's not needed! It doesn't even matter which wire you connect to which pin on the 2 wire VSS, (but if the colors match, connect them!)

Hope this helps!
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Unread 04-21-2012, 01:54 PM   #3
ymurf
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1979 CJ7 
 
Join Date: Apr 2011
Location: Steelville, Mo
Posts: 738
Quote:
Originally Posted by 1986cj View Post
I have copied this from cjoffroad, never tired it but guys say it works. The Early 2 wire VSS is a simple mechanical switch, it makes and breaks a set of contacts internally using magnets and a reed switch. One wire is from the PCM which has a 5 volt reference internally, the other is the sensor return. When the 5 volts drops to ground, the PCM senses a trigger.

The later 3 wire VSS uses a Hall effects switch to make and break the connection between the sensor return wire and the ground wire. The 3rd wire is a 5-8 volt power supply to operate the hall effect sensor.

The 3 wire sensor colors are usually:
Wt/Bk = 5-8v supply
Wt/Or = Sensor return (signal to PCM)
Bk/LB = Common sensor Ground

With the 2 wire sensors, just connect the 2 wires to the Bk/LB and Wt/Or wires from the harness, you can disregard the Wt/Bk = 5-8v supply wire, it's not needed! It doesn't even matter which wire you connect to which pin on the 2 wire VSS, (but if the colors match, connect them!)

Hope this helps!
Thats better than anything else I have found..Mine has an orange,A white with orange stripe and a black with blue stripe.So I am guessing I would disregard the orange wire?? Anyone else agree?
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Unread 04-21-2012, 02:06 PM   #4
1986cj
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1986 CJ7 
 
Join Date: Dec 2007
Location: Denver Colorado
Posts: 1,876
If I remerber right may have been from Marty So Cal, but not real sure. He hangs out over on priate and is real good with mpfi. The way I understand it is "you can disregard the Wt/Bk = 5-8v supply wire, it's not needed!"
Take a volt meter and see witch one has 5-8v and dont use it.
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Unread 04-21-2012, 02:11 PM   #5
ymurf
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1979 CJ7 
 
Join Date: Apr 2011
Location: Steelville, Mo
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Quote:
Originally Posted by 1986cj View Post
If I remerber right may have been from Marty So Cal, but not real sure. He hangs out over on priate and is real good with mpfi.
I made a post over there this morning but no response.
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Unread 08-03-2012, 05:04 PM   #6
Jak_Flash
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Join Date: Oct 2009
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Is the 2 wire hookup from the 91 vss considered a 2 pole vss? I'm in need of one for my 5.7tbi swap.
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