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    1. #1
      Join Date
      Nov 2010
      Posts
      251

      Just tried firing my ls2 for the first time

      I am running an LS2 with a t56 in my 68 firebird. I have a PSI harness. I flooded the fuel lines to clean em out before I tried firing it so I know I have fuel. It cranks real strong and sounds like it wants to start but it won’t turn over. What are some things I should look for to get it to turn over? Thank in advance.

    2. #2
      Join Date
      Aug 2004
      Location
      Jacksonville, FL
      Posts
      1,651
      Country Flag: United States
      It cranks but won’t turn over? Don’t understand that one. Do you have good fuel pressure at the rail? Any CEL codes?
      Chris
      1968 Chevy Camaro SS
      LS3/T56 DSE suspension


    3. #3
      Join Date
      Aug 2018
      Location
      Saginaw Mi
      Posts
      94
      Country Flag: United States
      ^ Im guessing he just meant it wont fire up. first things first, fuel, air, spark. You got fuel, now pull a plug and roll it over to make sure you're getting spark, and double check other things like sensors correlated with air flow.

    4. #4
      Join Date
      Apr 2006
      Location
      Huntington Beach, CA
      Posts
      2,415
      Country Flag: United States
      Fuel in the fuel rail doesn't automatically mean fuel in the engine. If you have sensor issues the ECU may not fire the injectors or the coil packs. Check for a code.
      Please Subscribe to the AutoXandTrack YouTube Channel

      Autocross and track blog about running autocross and track events with pro touring cars

    5. #5
      Join Date
      Feb 2018
      Posts
      27
      I had same issue with my LS2. I thought it was the VATS at first, but my problem was a error in the ECU. I had to re flash it and problem solved. But I know if the VATS is not disabled the engine will fire but it will not run.

    6. #6
      Join Date
      Nov 2010
      Posts
      251
      I pulled the fuel rail and tested all the injectors and cleaned them. Still had the same problem. Talked to psi and they think I need to set up the cold air and set the Maf sensor in the correct location. I also have a leak in my gas tank so once I get the new one in I’ll keep trying.

    7. #7
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Quote Originally Posted by firebirdzig View Post
      I pulled the fuel rail and tested all the injectors and cleaned them. Still had the same problem. Talked to psi and they think I need to set up the cold air and set the Maf sensor in the correct location. I also have a leak in my gas tank so once I get the new one in I’ll keep trying.
      Installation should be complete before starting the car. See a lot of guys try starting without a proper MAF or exhaust installation and it usually goes badly....

      What tune did PSI give you? They have the mindset that it just needs to run well enough to get dyno tuned.

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

    8. #8
      Join Date
      Nov 2010
      Posts
      251
      I don’t recall the exact tune that was given. I always planned on taking it to the dyno after getting it running to get the ecu dialed in. When I bought the harness I wasn’t sure about the cam, gears ect.

    9. #9
      Join Date
      Aug 2007
      Posts
      641
      My first check is the computer turning on the fuel pump when the key is turned? It should run for a few seconds and then should shut off if the computer doesn't crank rotation. Check for fuel PSI at the fuel rail. Should be 58 psi. Double check all electrical connectors on the engine are fully plugged in. Most harness/ECM suppliers will supply a "stock" tune that will run rich. It should start and run. Is your LS2 drive by wire or drive cable throttle? On my drive by cable LS swaps I've had to open up the throttle blade slightly with the set screw to keep it running. Even if the MAP sensor is in the wrong place it should still start and run. Having said that the tuner that I use says if the map sensor is mounted directly to the throttle body they can be a real pain to tune properly. Check spark as said above. Check to see if the injectors are firing. Make sure the injector main connectors not switched left to right. Same with the coil wires. I haven't used PSI so I don't know how well everything is labeled but I seem remember a post on LS1 Tech said the ground and power wires on a PSI harness can be a bit confusing. Not flaming PSI but I would just double check. Hope this helps.

    10. #10
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Where is the ECU power drawn from? Wherever it is, that circuit needs to be hot both when the ignition key is in the RUN position and in the CRANK position. Many circuits are shut down in CRANK. Check to see that the ECU has power when cranking. Don't need a MAF to start.

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    11. #11
      Join Date
      Aug 2007
      Posts
      641
      I forgot about the start and run. Double check that.

    12. #12
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Quote Originally Posted by 79 Camaro View Post
      I forgot about the start and run. Double check that.
      People miss this all the time!

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    13. #13
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Aside from the potential powering issues I recommend you finish the intake and exhaust before you go any fiurther. No need for half@ssing around. The time saved is not worth it....

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

    14. #14
      Join Date
      Nov 2010
      Posts
      251
      The ecu is drawing power from the ignition wire on the American auto wire set up. I finished the intake the other day, waiting for some new tank bolts to get the tank put back in. It’s looking like next week to get back out there and try to fire it again.

    15. #15
      Join Date
      Nov 2010
      Posts
      251
      So I got out there today after finishing up the intake and putting in the new tank. It’s all together now minus the exhaust (just have the headers on). It will start but only if I hold down the gas pedal and as soon as I let off the pedal it dies. Not really sure what to make of that.

    16. #16
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Depending on where the O2 sensors are on your headers they likely will not read properly without some length of exhaust pipe connected. Most likely not the cause of your problem but those O2 sensors will likely read lean.

      Hopefully an expert will weigh in...

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

    17. #17
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Are you using the correct pedal for your harness? There are pinout differences between the various pedals as far as I know.

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

    18. #18
      Join Date
      Jul 2006
      Location
      Pensacola, FL
      Posts
      1,263
      Country Flag: United States
      Is the LS2 a 24x or 58x? If its a 58, did you happen to also get the ecm from PSI? If you did, hook a code reader up and see what what vehicle comes up for the ecm. I had a similar issue with a PSI ecm. I purchased an ecm for a 58x LS2. I had trouble getting the car started from day 1. Once started, ran fine. Sometimes I had to shoot carb spray in the intake to get it to start. When I scanned the ecm, 2008 corvette vin was in the E38 ecm. PSI said they dont have LS2 E38s, the use LS3 files- And just make the needed changes for TB, MAP sensor, and a couple other parameters. After much back & forth, I bought a blank E38 and had an LS2 corvette VIN loaded on the E38 at the dealer. All problems went away. I wasted 6 months on this, just something to keep in mind if you have trouble finding the problem once everything is finished on the car.



    19. #19
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Quote Originally Posted by Z06vet View Post
      Is the LS2 a 24x or 58x? If its a 58, did you happen to also get the ecm from PSI? If you did, hook a code reader up and see what what vehicle comes up for the ecm. I had a similar issue with a PSI ecm. I purchased an ecm for a 58x LS2. I had trouble getting the car started from day 1. Once started, ran fine. Sometimes I had to shoot carb spray in the intake to get it to start. When I scanned the ecm, 2008 corvette vin was in the E38 ecm. PSI said they dont have LS2 E38s, the use LS3 files- And just make the needed changes for TB, MAP sensor, and a couple other parameters. After much back & forth, I bought a blank E38 and had an LS2 corvette VIN loaded on the E38 at the dealer. All problems went away. I wasted 6 months on this, just something to keep in mind if you have trouble finding the problem once everything is finished on the car.
      Interesting. PSI also sent me a junk tune. L92 tune for an LS6. I caught it before I used it and sent it all back. They told me the tune would be good enough to get it started and limp to a dyno tune...

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

    20. #20
      Join Date
      Nov 2010
      Posts
      251
      The pedal is the one I told them I would be using when I bought the harness. I’ll have them double check tomorrow when I call them.

      As for the tune I wouldn’t even know how to check what the tune is on it (my LS2 is a 58x). I’ll see what kind of info I can get from them when I call. Hopefully it’s just the wrong pedal for the tune and if not I’ll have to look into getting a blank ecm you spoke of.

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