TBI Harness Question (1 Viewer)

[Leaping Deer]

I'm in the process of swaping in a TBI 350 out of a 91 Chevy G20 Conversion van. I will be running a SM465 with a factory 3spd t-case using a Woody style plate adapter. I have looked at Woody's tech link and read numerous threads on the subject. This 40 is to be done on the cheap to get me out on the trail so I don't have the cash to buy a wiring harness so I need to come up with my own.

Woody says to retain the VSS but remove the DRAC. I understand the reason to keep the VSS but I'm not sure how to bypass the DRAC. I was looking at the Jags that Run VSS and it appears that I need the 2 pulse version. Now how do I hook it up with eliminating the DRAC. The VSS has two wires (Lt. Green/Black) and (Purple/White) coming into the DRAC both listed as VSS input. Now I'm guessing the only two wires I would matter on the output would be the ECM Signal (Brown) and the RWAL Signal (White) which goes to both the RWAL module (which I'm guessing I don't need) and the ALDL Connector which I assume I would want to connect.

Would I just hook up the (Lt.Green/Black) to the (Brown) and the (Purple/White) to the (White) and call it good? Or do I just hook them all up together?

I'm sure I will have other questions and I will add them later.

 

[Leaping Deer]

Anyone out there build their own tbi harness?

 

[reddingcruiser]

VSS/DRAC

I did, but I'm running the 700R4 and I used a VSS from Downey/Tojo Products. Mine is also a '91 and is a 2 pulse version. I built my harness from the stock donor vehicle. Cheap but took a lot of time playing with spagetti.
Here is some information from a web site I used.
Digital Ration Adapter Controller (DRAC) and Vehicle Speed Sensor Buffer (VSSB) are both electronic devices that simply convert the input AC signal (from the VSS) to a calibrated digital DC signal. The DRAC sends 2,000 digital pulses per mile to the ECM (Electronic Control Module), 4,000 digital pulses per mile to the cruise control module, and 128,000 digital pulses per mile to the ABS (Anti-Lock Brake) computer. The DRAC and VSSB units are pre-calibrated from the factory according to the vehicle's stock gear ratio, and tire size. But, it can be re-calibrated by simply moving jumpers around. 1990-1991 vehicles should have the DRAC, and 1992-1995 vehicles should have the VSSB unit. The main difference between the DRAC unit and the VSSB unit (from what I can tell) is that the VSSB unit has an extra "bank" of 7 jumpers in addition to the same bank of 7 jumpers that the DRAC unit has. I would assume this extra bank of jumpers is for the electronically controlled transmission that GM started using in 1992.
It would appear you can remove the DRAC. Check out this site and see if it makes things any clearer GM DRAC/VSSB Calibration

 

[Downey]

(1) You don't need a DRAC at all. They are vehicle specific, not re-programable by the do-it-yourselfer, and only used to calculate for specific tire size used on a specific vehicle when all vehicles use the same ECU (i.e. C-10 Pickup and Astrovan may have same engine and ECU, but a completely different tire size).
(2) The two pulse VSS from Stealth has two white wires, not directional. Attach one of the wires (either one) to any ground, the other to the ECU's VSS input wire (normally brown wire entering port #437 on the ECU). You do not need to correct the two pulse signal unless you are additionally using an electronic speedometer (in which case you'd have other issues), or you are using such a large tire diameter that you've taken the ECU out of it's operating window. In these cases you'd use a Dakota Digital "signal interface" to correct the signal.