Ls wiring

Discussion in 'High Tech Retrofits' started by Goat, Mar 15, 2017.

  1. Goat

    Goat Veteran Member Lifetime Gold Member

    1,594
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    Jun 7, 2001
    moncure, NC
    Starting to wire my car. I have a Painless full chassis harness to integrate with a GM ECM/engine harness, along with Vintage Air wiring. I am finding some redundancies and wondering if there are any implications.

    The first one is powering the fuel pump. I know I need a switched power source. Both Painless and the GM harness have provisions for this. I am leaning towards using the Painless one because it routs both a power and fuel sending lead with the rear tail lights - making it convenient to the in-tank pump. I can't see any reason not to use this one. Any thoughts on this?

    Also, if anyone has installed both of these systems, I would be interested in any other quirks that may await me...

    thanks.
     
  2. badazz81z28

    badazz81z28 Veteran Member

    13,742
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    May 4, 2001
    Las Vegas, NV
    Richard I have vintage air, painless harness and the engine harness working together. Fire away Qs

    I can tell you your better off letting the engine harness control engine functions. The fuel pump is controlled by a relay controlled by the ECM.
     
    Last edited: Mar 15, 2017
  3. badazz81z28

    badazz81z28 Veteran Member

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    May 4, 2001
    Las Vegas, NV
    Ok now that I have a second. I used the fused power source from the painless harness for "fuel pump" to the standalone harness relay. I only did this because the PSI harness doesn't have a fused power source for the pump. The power for the pump has to come from the ECM controlled relay. The ECM will turn the pump on or off depending on if the engine is running regardless of switched power. The power source being switch by the relay can come from the painless harness but honestly it doesn't even have to be ignition switches power. I'll have to look if the GM one does. Vintage air, I used the brown trigger wire from the painless harness to be the switch for the VA kit. The VA will also need a batt source as well as your harness (straight to the battery, starter, stud etc). I put mine on a bulkhead stud on the tunnel because my battery is in the trunk. For trigger source for the harness I used the HEI power wire. Worth noting I removed a handful of wires out of the painless harness as they are not needed.
     
  4. Goat

    Goat Veteran Member Lifetime Gold Member

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    Jun 7, 2001
    moncure, NC
    Thanks. I'm going to have to read your first few sentences a few times. Confused me a little - must be too early...
    1st, what is the "PSI harness"?

    So, you used the Painless "fuel pump" wire to activate a relay, but the power from the relay to the pump has to come from the ECM? Where is this relay, in the GM fuse box? I haven't sorted through all the GM stuff yet...

    I too have mounted my battery in the trunk.
     
  5. badazz81z28

    badazz81z28 Veteran Member

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    May 4, 2001
    Las Vegas, NV
    PSI is just the brand of the harness I used with the LS1.

    The Fuel Pump wire from the Painless harness will be the source power for the pump. The ECM will provide the trigger power for the relay to let the voltage from the painless to the pump flow.
     
  6. 71RS/SS396

    71RS/SS396 Veteran Member

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    Aug 26, 2008
    Wake Forest NC
    I would let the engine harness control any engine function...fuel pump, fans...etc. It's safer for the ecu to be in control of the fuel pump because it will shut down the pump once it loses rpm feedback.
     
  7. Goat

    Goat Veteran Member Lifetime Gold Member

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    Jun 7, 2001
    moncure, NC
    Thanks guys. I've had some time to read through the instructions for the GM harness now. I agree that using whatever the ECM offers is the best way to go. Thanks.
     
  8. Mwilson

    Mwilson Veteran Member

    No helpful info but I'm gonna have to stop by and check it out
     
  9. Squeaky192

    Squeaky192 Veteran Member

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    Aug 19, 2014
    Fort Worth, TX
    I believe the ECM provides a ground trigger to the fuel pump relay, and if it sees low oil pressure, it should cut off the pump, at least when set up like a factory harness. I'd assume the GM harness is the same way, and you could just cap off our chassis harness fuel pump wire and keep it around in case you need a 12V ignition switched wire for anything moving forward. The GM harness works well, but you're going to have a fun time if you are trying to hide that giant fuseblock they have. :p

    The chassis harness is meant to work on everything from a stock carb'd car, to a guy wanting to update to a simple low amperage fuel pump, to someone like you LS swapping. I removed quite a few wires out of my chassis wiring, as I didn't need the sending unit wires under the hood with my Dakota Digital gauges, etc.
     
  10. Mwilson

    Mwilson Veteran Member

    where are the pics!!!
     

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