Announcement

Collapse
No announcement yet.

LS swap - No Start the next day

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • LS swap - No Start the next day

    Hi,

    I have a Pro-Flo 4 system that I am using on an LS2 out of a 2005 Pontiac GTO.

    I have been using this system in a Subaru for almost a year and it has been working great. (It was running for 6 months on a single plane/4150/edlebrock 3636 injectors with a 5.3 LS1 with no problems of any kind)

    Now for some reason the car will not start.

    My current setup:

    LS2 - with 24x crank/1x cam
    FAST 102mm and 102mm throttle body
    LS3 oem injectors (35lb/h at 43psi)
    43 psi fuel pressure
    stock coils
    stock LS7 exhaust
    AEM CD-7 hooked up to CAN

    The car has ran with all this for 2-3 months but only for a few minutes at a time. I was moving it around the shop to work on it. I had a constant issue where it would stall out after revving at idle. I raised idle to 900 and played with the throttle stop to lower IAC down to 10% and it would still hunt for idle after revving. Idle would stay smooth once the rpms would stop changing rapidly.

    I ran the car at idle for 30 minutes and let it fully warm up but it would still hunt for idle after blipping the throttle at idle. I turned it off and disconnected the battery. After 4 hours I came back to the car and reconnected the battery and the car will not start, but it does crank.

    Things I have done or have confirmed working: (not neccesarily in this order)
    Replaced the battery but that didn't help. I thought maybe the voltage was dropping too much down to 10-10.5volts.
    Attached a battery charger while cranking. I have 14 volts before cranking with the charger on and it drops down to ~11.5 volts while cranking. I have tested voltage at the battery wire for the PF4 and the ignition wire for the PF4. Neither drop out or go below battery voltage even when starter is engaged. Voltages without charger are 9.5-10.5volts while cranking and 11.3-12.1 with ignition only. Depends on battery charge.

    Replaced MAP sensor with a new one. ~1.8inHg when cranking, ~0 when not.
    Fuel pump uses a relay controlled by the PF4, fuel pump has battery voltage and fuel pressure is 43psi while cranking.
    Fuse at PF4 has same voltage as battery.
    I have not tested fuel injectors for voltage but O2 sensor shows ~14 to ~16 AFR while cranking, if I let the sensor become ready
    I have not checked for spark or pulled the plugs.
    All diagnostic lights are always green
    I have tried many different maps even though the car already ran on one before. 323,346,361 CID, stock/mild/race cam, LS firing order, 24x crank, 43psi base, 35/lb hr.
    RPM while cranking at 160-180 (depends on voltage at battery)
    Changed cam and crank sensors, V+ same as battery, ground is present, signal is at 4.9v
    IAT is at ambient, coolant is at ambient.
    Tried changing cranking fuel and cold start enrichment max/min values

    Only weird thing is a light smell of oil out of the exhaust but I have the valve covers venting into the air filter via catch cans. No oil in the intake, just oil vapor smell.

    Any ideas, before I buy a new ecu?
    Anything that would cause the PF4 not to fire injectors or coils?
    Last edited by Sway Tale; 10-08-2020, 01:01 PM.

  • #2
    READ NUMBER 4 FROM PAGE 3 OF MANUEL.

    1. BATTERY CHARGER PRECAUTIONS: PLEASE ADHERE TO THE FOLLOWING GUIDELINES OR DAMAGE TO ECU MAY OCCUR.
    • Be sure the battery has a full charge prior to attempting to start the vehicle.

    2 • Never use the “engine start or jump start” setting on a charger to start the engine.

    3 • Do not set the battery charger above 10 amps when charging.

    4 • Never turn on the ECU or attempt to start the engine with the battery charger connected

    5 • Make sure the charger is not charging over 18.0 volts.

    6 • If the battery is completely discharged, it is best to disconnect the negative terminal on the battery when charging
    Last edited by fleet man; 10-08-2020, 12:36 PM.

    Comment


    • #3
      Sorry, I edited my post in bold to make more sense.

      Comment


      • #4
        You need to check for spark.
        At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

        Comment


        • #5
          with all the in shop running [ i.e not driving enough ] are the spark plugs fouled ? and as asked check for spark

          Comment


          • #6
            Forgot: The #1 reason LS motors don't start, is no/bad ground for the ignition coils....4 coils on each head are grounded to each head. Then each head is grounded to firewall, or frame.

            #2 is wrong wires connected to Crank/Cam sensor.....some motors have a short extension cable ( factory ). They switch the wires around in this short cable......butt this is always a "no start at first running of motor".
            At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

            Comment


            • #7
              Originally posted by fleet man View Post
              with all the in shop running [ i.e not driving enough ] are the spark plugs fouled ? and as asked check for spark
              Originally posted by BITE_ME View Post
              You need to check for spark.
              Originally posted by BITE_ME View Post
              Forgot: The #1 reason LS motors don't start, is no/bad ground for the ignition coils....4 coils on each head are grounded to each head. Then each head is grounded to firewall, or frame.

              #2 is wrong wires connected to Crank/Cam sensor.....some motors have a short extension cable ( factory ). They switch the wires around in this short cable......butt this is always a "no start at first running of motor".
              That was it. No spark. Ground wire for coils was not connected. I didn't bother testing for spark, I tested the pins at the R plug for coils and PIN A had battery voltage on it (voltage feedback from coils still connected to L). PIN A on the coil connector is labeled on the harness as a ground, its the ring terminal with short wires that you would normally bolt down next to the rear cam sensor (There is a conveniently threaded hole in the block for this). I assumed this was a common ground to the PF4 ecu and if not connected then the sensors wouldn't work . After looking at the diagrams it only goes to the coils. In my infinite wisdom I bolted it to the RH cylinder head but never tightened the bolt. Apparently it worked its way loose. This is very embarrassing.

              The cam sensor wiring needs to be corrected as well. Swapped pins from A to C on plug going to front cover cam sensor. This is why the car would start poorly and stall out after blipping the throttle. Is it true that the PF4 is setup for wasted spark?

              I do have a lingering issue. Once coolant is at 190F, when I blip the throttle and rpms go back down to idle the rpms and IAC% will surge trying to hit target idle. The rpms can go as low as 350 when this happens. Raising idle RPM to 1000 helps mask this but that is not a solution. IAC% also changes on its own. Sometimes it goes down to 5%, other times it stays at 20%. I tried to adjust the throttle stop again but I can't tell if it helps. When cold the engine starts immediately when cranking, when hot it takes longer. Vacuum leak at intake manifold, maybe?

              Comment


              • #8
                Yes to wasted spark. 4 coil drivers built into the system:

                You fire 2 coils at once. Example for a SBC with firing order of 1-8-4-3-6-5-7-2.
                Driver 1: Cylinders 1 ( Firing ) and it's companion Cylinder 6 ( exhaust ).
                Driver 2: Cylinder 8 ( Firing ) and it's companion Cylinder 5 ( exhaust ).
                Driver 3: Cylinder 4 ( Firing ) and it's companion Cylinder 7 ( exhaust ).
                Driver 4: Cylinder 3 ( Firing ) and it's companion Cylinder 2 ( exhaust ).
                So.
                Driver 1: Cylinder 6 ( Firing ) and it's companion Cylinder 1 ( exhaust ).
                Driver 2: Cylinder 5 ( Firing ) and it's companion Cylinder 8 ( exhaust ).
                Driver 3: Cylinder 7 ( Firing ) and it's companion Cylinder 4 ( exhaust ).
                Driver 4: Cylinder 2 ( Firing ) and it's companion Cylinder 3 ( exhaust ).

                Do you see the pattern?

                You take the firing order: 1-2-3-4-5-6-7-8
                The first Cylinder will fire with the fifth in the order.
                The second number in the order, will fire with the sixth number in the order.
                The third number in the order, will fire with the seventh number in the order.
                The fourth number in the order, will fire with the eighth number in the order.

                This works on all V8 firing orders.

                Anyway.

                To check for vacuum leaks.
                Plug the IAC port, and close the throttle all the way......vacuum leak will give the air needed to keep the motor running....you can also spray carburetor cleaner around the base......my factory LS was kind of hunting at idle, and not being consistent with the RPM's at idle. It was the intake gaskets.
                At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

                Comment


                • #9
                  Originally posted by Sway Tale View Post





                  That was it. No spark. Ground wire for coils was not connected. I didn't bother testing for spark, I tested the pins at the R plug for coils and PIN A had battery voltage on it (voltage feedback from coils still connected to L). PIN A on the coil connector is labeled on the harness as a ground, its the ring terminal with short wires that you would normally bolt down next to the rear cam sensor (There is a conveniently threaded hole in the block for this). I assumed this was a common ground to the PF4 ecu and if not connected then the sensors wouldn't work . After looking at the diagrams it only goes to the coils. In my infinite wisdom I bolted it to the RH cylinder head but never tightened the bolt. Apparently it worked its way loose. This is very embarrassing.

                  The cam sensor wiring needs to be corrected as well. Swapped pins from A to C on plug going to front cover cam sensor. This is why the car would start poorly and stall out after blipping the throttle. Is it true that the PF4 is setup for wasted spark?

                  I do have a lingering issue. Once coolant is at 190F, when I blip the throttle and rpms go back down to idle the rpms and IAC% will surge trying to hit target idle. The rpms can go as low as 350 when this happens. Raising idle RPM to 1000 helps mask this but that is not a solution. IAC% also changes on its own. Sometimes it goes down to 5%, other times it stays at 20%. I tried to adjust the throttle stop again but I can't tell if it helps. When cold the engine starts immediately when cranking, when hot it takes longer. Vacuum leak at intake manifold, maybe?


                  thank you for your honest response to help others to tell of what went wrong and as a tech for 40 years it helps to be honest of our mistakes so others will follow your lead.

                  Comment


                  • #10
                    i had the issue the first time i tried to start my ls...didnt connect the ground to the block... once i figured out it scared me how quickly it came to life...

                    Comment


                    • #11
                      Originally posted by Sway Tale View Post


                      I do have a lingering issue. Once coolant is at 190F, when I blip the throttle and rpms go back down to idle the rpms and IAC% will surge trying to hit target idle. The rpms can go as low as 350 when this happens. Raising idle RPM to 1000 helps mask this but that is not a solution. IAC% also changes on its own. Sometimes it goes down to 5%, other times it stays at 20%. I tried to adjust the throttle stop again but I can't tell if it helps. When cold the engine starts immediately when cranking, when hot it takes longer. Vacuum leak at intake manifold, maybe?
                      I figured this one out too. The engine is blown. Cylinders 1 and 7 covered the spark plugs in oil.

                      Comment


                      • #12
                        Originally posted by Sway Tale View Post

                        I figured this one out too. The engine is blown. Cylinders 1 and 7 covered the spark plugs in oil.

                        Thanks, for the update.....

                        A reminder " Mechanical " problems , can throw off Pro Flo EFI diagnosis.....

                        Comment


                        • #13
                          O2 sensor might be gone now. It can't be cleaned.
                          At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

                          Comment

                          Working...
                          X