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1990 TBI setup in an 86 K-5

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by btolenti, Dec 21, 2004.

  1. btolenti

    btolenti 1/2 ton status

    Sep 28, 2003
    Likes Received:
    Gilroy, CA
    I can get a setup from a 90 truck that came with a 350 to replace my CCC Q-jet in my 86 K-5. What do I do about the VSS???? The TBI setup should have this, right? Unfortunately my 86 is the old speedo cable setup....
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    The VSS in your truck now should work with the ECM for the 1990, since the 199x DRAC just converts that 40 pulse signal to what the ECM wants, which in 1990, should still be 2 pulse (1000 cable revolutions per mile, times 2 pulses per cable revolution=2000PPM at the ECM) which is what the optical VSS you have now is.

    The ECM for the '90-91 trucks is a 1227747.

    The only variable in your situation is what output from the DRAC is the '747 using. DRAC shows the pinout for the DRAC. As you can see, there are multiple 2000PPM outputs, but there is also 40PPR, 128,000PPM, and 4000PPM. There might be data out there on the web that spells it out that I haven't found, but I kind of think not. DRAC just isn't real popular.

    However, if you are getting the setup, check the DRAC wiring, see which pin on the ECM the DRAC output goes to. I'd be willing to bet it's from one of the 2000PPM pins. At that point, just wire the VSS ECM output you have now to that pin on the new ECM.

    I'm going through this myself, essentially the same thing...going from 1988 injection to a 1991 205, which of course also uses no speedo cable. I was able to figure out that the stock truck VSS output I have now, (speedo cable driven) is the same as the DRAC 2000ppm output, which is why I believe the '747 you have uses the same.

    Hope this helps.

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