7747 VSS Wiring Question
07-13-2006, 06:03 PM
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7747 VSS Wiring Question
I feel kinda dumb, but I looked, and searched and couldnt find my answer...
Anyway, this is for a system that was put on a non-GM vehicle.
I am trying to put the VSS back in the circuit. the VSS itself has 2 wires, the 7747 pinout shows A10 as the VSS circuit.
My question is, where do the 2 wires from the VSS itself go? One wire to the A10 position on the ECM, the other to ..??? Ground?
Anyway, this is for a system that was put on a non-GM vehicle.
I am trying to put the VSS back in the circuit. the VSS itself has 2 wires, the 7747 pinout shows A10 as the VSS circuit.
My question is, where do the 2 wires from the VSS itself go? One wire to the A10 position on the ECM, the other to ..??? Ground?
07-14-2006, 08:48 AM
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Engine: check
Transmission: check
It depends upon what kind of VSS you have. One with just 2 wires is most likely a magnetic unit. In this case you will need a 4-out Buffer Box. This box converts the 4-pole mag VSS to a square wave output. That output goes directly to the ECM.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
07-14-2006, 12:32 PM
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Thanks RBob
I do have a spare DRAC here, so Ill start with that first.
Now that would lead me to the next question:
DRAC PINOUT
connector 1
-- speedo output
-- N/C
-- speed to computer
-- speed sensor input
-- N/C
-- speed to rwal
-- 12 v keyed
-- ground
-- speed sensor input (sometimes used instead of other one can be empty)
If that is the correct pinout for the DRAC (im not sure), im back to my original problem of where the 2nd wire goes from the VSS?
I do have a spare DRAC here, so Ill start with that first.
Now that would lead me to the next question:
DRAC PINOUT
connector 1
-- speedo output
-- N/C
-- speed to computer
-- speed sensor input
-- N/C
-- speed to rwal
-- 12 v keyed
-- ground
-- speed sensor input (sometimes used instead of other one can be empty)
If that is the correct pinout for the DRAC (im not sure), im back to my original problem of where the 2nd wire goes from the VSS?
07-14-2006, 12:45 PM
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Car: 75 Jeep Wagoneer
Engine: AMC 360
Transmission: TH400
Could be wrong, but I think that one would go to the input and the other to a ground.
Last edited by 75 wagon; 07-14-2006 at 12:50 PM.
08-28-2007, 05:19 PM
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Re: 7747 VSS Wiring Question
I want to use one of these for a VSS.
http://store.summitracing.com/partde...6+&appfilter=1
Would one of the mentioned devices work for this? If not how could I make this work for a TBI system? Or is there something simillar available that would work better?
Thanks.
http://store.summitracing.com/partde...6+&appfilter=1
Would one of the mentioned devices work for this? If not how could I make this work for a TBI system? Or is there something simillar available that would work better?
Thanks.
It depends upon what kind of VSS you have. One with just 2 wires is most likely a magnetic unit. In this case you will need a 4-out Buffer Box. This box converts the 4-pole mag VSS to a square wave output. That output goes directly to the ECM.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
Last edited by Binder; 08-28-2007 at 05:37 PM.
08-28-2007, 11:09 PM
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Car: 75 Beast
Engine: 383 +EBL Flash
Transmission: 700R4
Axle/Gears: 4.11 with 33"
Re: 7747 VSS Wiring Question
TBI jr.
I'm putting finishing touches on my converted '75 C20 to a TBI. I bought my VSS from JTR. It's a two wire, 2000 pulse per mile unit. I placed my DVM (in resistance mode) across the two leads and made couple of revolutions of the shaft. It appears that JTR unit is a magnetic interrupter (switch on/off) unit. On 7747, A10 is pulled high through ECM internal pull-up resistor to +12Vdc while VSS pulls it down from 12 V to 0.6 volts as it rotates. 0.6 volts due to open collector in DRAC unit - so just one forward biased diode junction to ground on the other lead of VSS should do.
//RF
I'm putting finishing touches on my converted '75 C20 to a TBI. I bought my VSS from JTR. It's a two wire, 2000 pulse per mile unit. I placed my DVM (in resistance mode) across the two leads and made couple of revolutions of the shaft. It appears that JTR unit is a magnetic interrupter (switch on/off) unit. On 7747, A10 is pulled high through ECM internal pull-up resistor to +12Vdc while VSS pulls it down from 12 V to 0.6 volts as it rotates. 0.6 volts due to open collector in DRAC unit - so just one forward biased diode junction to ground on the other lead of VSS should do.
//RF
Last edited by RFmaster; 08-28-2007 at 11:13 PM. Reason: add
08-29-2007, 11:13 AM
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Re: 7747 VSS Wiring Question
Binder, the one you show on Summit claims to be both programmable, and a 16 pulse per revolution sender. Although I have a feeling the speedometer that Automotive offers is programmable, not the sender. The 16 pulses per revolution is too high.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
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08-29-2007, 03:25 PM
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Re: 7747 VSS Wiring Question
I don't have a speedo, just want ECM input. Sounds like the JTR unit that RF master listed would be perfect for me and I could wire it straight to the ECM?
This one.
Speed Sensor, 2PRS
The two-pulse (2000 pulses per mile) square wave (D.C. current or direct current) used on all TBI engines through 1992, all computer-controlled-carbureted engines, and on 1985–1989 TPI engines.
This one.
Speed Sensor, 2PRS
The two-pulse (2000 pulses per mile) square wave (D.C. current or direct current) used on all TBI engines through 1992, all computer-controlled-carbureted engines, and on 1985–1989 TPI engines.
Binder, the one you show on Summit claims to be both programmable, and a 16 pulse per revolution sender. Although I have a feeling the speedometer that Automotive offers is programmable, not the sender. The 16 pulses per revolution is too high.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
Last edited by Binder; 08-29-2007 at 03:39 PM.
11-15-2010, 05:34 PM
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Re: 2-pulse VSS Wiring Question
The question about where the "OTHER" end is wired, remains unanswered.
Anybody out there, swapped a TPI into a Classic Chevy, and KNOWS where the two wires go!?
Exasperated!
Anybody out there, swapped a TPI into a Classic Chevy, and KNOWS where the two wires go!?
Exasperated!
Binder, the one you show on Summit claims to be both programmable, and a 16 pulse per revolution sender. Although I have a feeling the speedometer that Automotive offers is programmable, not the sender. The 16 pulses per revolution is too high.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
The TBI optical pickup (off the speedo) is 2 pulses per rev. It goes directly to the ECM.
The TBI magnetic pickup (off the trans) is 4 pulses per rev and is buffered and divided by 2. Then goes to the ECM.
These both give the 2000 pulses per mile RF posted about.
The Autometer one can be used if the output is divided down to 2 pulses per rev. Easy to do with some CMOS chips. Then use a transistor (PN3904) in an open collector form to drive the ECM input.
RBob.
12-12-2010, 11:24 PM
#10
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Re: 2-pulse VSS Wiring Question
I bought i signal converter from Dakota digital. It was simple to install, and came with good instructions.sorry i cant remember the wiring exactly. but the part # is SGI-5 Universal Signal Interface Unit. it works great for me. And if you do an online search on 1227747 pin out, and drac. there are diagrams to follow. good luck. also if you ever want to change set ups. just move a jumper and push some buttons and your done.. its pretty slick.
Last edited by JeepYJv8; 12-12-2010 at 11:27 PM. Reason: add something
12-13-2010, 07:36 AM
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Re: 2-pulse VSS Wiring Question
A digital sensor has one wire grounded.
RBob.
08-13-2017, 05:54 PM
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Re: 7747 VSS Wiring Question
It depends upon what kind of VSS you have. One with just 2 wires is most likely a magnetic unit. In this case you will need a 4-out Buffer Box. This box converts the 4-pole mag VSS to a square wave output. That output goes directly to the ECM.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
The 4-out box can be found in a bunch of different GM cars. '88-'92 TBI Firebirds and Camaros, earlier MAF TPI cars, and Caprice's of the same vintage. Label on box actually has '4-OUT BUFFER' on it.
Can also use a DRAC as it too will buffer a mag sensor. And, has the benefit of allowing to adjust the VSS PPM into the ECM. Depending upon what you are doing, it may be the better choice.
If you get a square wave output sensor, it is 3 wires, +Ign, grnd and ECM input.
RBob.
ques.If this pu needs VSS signal going to ecm to run right and the ecm needs vss to input 2000ppm ,how do I go cheapest route to get there? The guy still wants his factory speedo,which is cable driven.
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