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    Results 1 to 8 of 8
    1. #1
      Join Date
      Sep 2017
      Posts
      655
      Country Flag: United States

      LS7 backfire initial startup E39 ecu

      Ok guys here we go. LS7 with Late model racecraft cam and heads. Purchase out of a wrecked Z06 2008 model.
      I converted to wet sump so I changed the timing set to a Katech while there and a melling high volume oil pump. Using a psi swap harness HAR-1037 and the gm E38 ecu that came with the wreck.
      I got 59-60 lbs of fuel pressure.
      It backfires a few times the first time I tried startup. Thought maybe the intake was sucking air since a smell a little fuel I think. ( My sniffer sucks since covid) but so I tightened intake some more. It fired up and sounded smooth at about 1500 then one more backfire.
      I haven't scanned yet because my tech 2 was at my town shop and I'm home.
      Any suggestions to start trouble shoot.
      I'm new to LS but hot rodder and heavy quip mechanic for 30 years.
      Advice needed.
      TANKMASTERJ
      https://www.pro-touring.com/threads/...touring-Camaro
      Jasons Toys
      67 Camaro build
      2000 HD Softail
      1989 CBR Hurricane anniversary edition

    2. #2
      Join Date
      Sep 2004
      Location
      Santa Barbara, Ca
      Posts
      1,042
      I don’t have an answer, but was it backfiring through the intake or the exhaust?
      Andy

      1967 Camaro RS
      Magnacharged LS1/T56
      543 rwhp, 516 rwtq
      Sold

      1968 Firebird
      LS427/570 and T56 Magnum
      swap in progress



    3. #3
      Join Date
      Jun 2016
      Location
      Upstate NY
      Posts
      41
      Stuck/plugged or questionable injector(s), plug/wire. Is the tune correct? If the tune is off that's another place to start. If it runs fine at 1500, i'll start with injectors. Good news is you have a GM ECU, so monitoring and trouble codes make it easy to problem solve. With a Holley Dominator, much more difficult.

    4. #4
      Join Date
      Sep 2017
      Posts
      655
      Country Flag: United States
      Quote Originally Posted by ORBandit View Post
      Stuck/plugged or questionable injector(s), plug/wire. Is the tune correct? If the tune is off that's another place to start. If it runs fine at 1500, i'll start with injectors. Good news is you have a GM ECU, so monitoring and trouble codes make it easy to problem solve. With a Holley Dominator, much more difficult.
      An aftermarket coil harness with two separate pluds and 2 wires flip flopped in each. It's all good now.
      And I do got a GM ECU 38. For some reason my Tech 2 Scanner wasn't catching it bjt I didn't run it long.
      Maybe that's why.

      - - - Updated - - -

      Quote Originally Posted by streetk14 View Post
      I don’t have an answer, but was it backfiring through the intake or the exhaust?
      Exhaust. But as posted below it was coil harness with wires flip flopped on 3 and 7. It runs fantastic now
      TANKMASTERJ
      https://www.pro-touring.com/threads/...touring-Camaro
      Jasons Toys
      67 Camaro build
      2000 HD Softail
      1989 CBR Hurricane anniversary edition

    5. #5
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,072
      Country Flag: United States
      Quote Originally Posted by TANKMASTERJ View Post
      An aftermarket coil harness with two separate pluds and 2 wires flip flopped in each. It's all good now.
      And I do got a GM ECU 38. For some reason my Tech 2 Scanner wasn't catching it bjt I didn't run it long.
      Maybe that's why.

      - - - Updated - - -



      Exhaust. But as posted below it was coil harness with wires flip flopped on 3 and 7. It runs fantastic now
      Nice troubleshooting. Things like that can be tough to find.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain

    6. #6
      Join Date
      Sep 2017
      Posts
      655
      Country Flag: United States
      Quote Originally Posted by dhutton View Post
      Nice troubleshooting. Things like that can be tough to find.

      Don
      Thanks Don
      I'm old to engine electrical on heavy equipment, dozer, excavators, compressors, cranes, etc, and multiple diesel trucks heavy and medium duty but this is my first LS swap so I'm learning alot.
      TANKMASTERJ
      https://www.pro-touring.com/threads/...touring-Camaro
      Jasons Toys
      67 Camaro build
      2000 HD Softail
      1989 CBR Hurricane anniversary edition

    7. #7
      Join Date
      Sep 2004
      Location
      Santa Barbara, Ca
      Posts
      1,042
      Quote Originally Posted by TANKMASTERJ View Post
      An aftermarket coil harness with two separate pluds and 2 wires flip flopped in each. It's all good now.
      And I do got a GM ECU 38. For some reason my Tech 2 Scanner wasn't catching it bjt I didn't run it long.
      Maybe that's why.

      - - - Updated - - -



      Exhaust. But as posted below it was coil harness with wires flip flopped on 3 and 7. It runs fantastic now
      Itís not the first time Iíve heard of that happening to someone. Who made that harness, out of curiosity?
      Andy

      1967 Camaro RS
      Magnacharged LS1/T56
      543 rwhp, 516 rwtq
      Sold

      1968 Firebird
      LS427/570 and T56 Magnum
      swap in progress



    8. #8
      Join Date
      Sep 2017
      Posts
      655
      Country Flag: United States
      I cannot remember but I bought it quote a while back. It was supposed to be a USA one I recall.

      TANKMASTERJ
      https://www.pro-touring.com/threads/...touring-Camaro
      Jasons Toys
      67 Camaro build
      2000 HD Softail
      1989 CBR Hurricane anniversary edition