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Started running terribly after about 5 mins.

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  • Started running terribly after about 5 mins.

    We've just finished an install of the Pro-Flo 4 on a 347 Windsor with around 500HP (Australian horsepower - on an engine dyno). The car seemed to idle great after going through the setup and was driving great for the first few minutes. AFRs looked good and everything felt very smooth considering how early in the process we were.
    Then it went pear shaped. I believe it started to misfire, which obviously sent the AFRs into a spin. It progressively got worse until we had to get the car towed home. Now it will barely fire.

    It's running a bosch GT40 (non-resistor) coil since that's what was on it before hand.
    Primary resistance is measuring about 4.5ohms.

    The plugs don't look fouled, but we're going to try changing the coil, leads and plugs. I hope it's one of these, otherwise I think it's pointing to the ECU.
    Is there any way to log the tach trigger on these units? I'm not used to such a "friendly" interface on an ECU.
    Last edited by hybrid; 04-12-2019, 01:17 AM.

  • #2
    If you haven't already, you need to read the latest instructions: https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/35760.pdf Notice the big warnings about coil selection.

    That's not a good coil to use however it's probably not the culprit to your problem. Change the coil to something on the list of acceptable coils or similar and see where that gets you. There is no logging with Pro-Flo 4 however, you can see if you have a valid position signal from the distributor by simply looking for RPM while cranking the engine. If it shows 0 then you have a distributor problem. It'll likely show 100-300 rpm in which case the distributor is fine.

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    • #3
      Make sure the distributor hasn't moved. Recheck that the base timing is correct.

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      • #4
        Have never seen an ECU tied to such a small selection of coils. Normally as long as the impedance is enough to keep current below the Max of the driver it's fine. The distributor hasn't moved.
        We have another MSD canister coil we can try, but I need to check the part number. It was connected to an electronic MSD distributor previously, so hopefully it is on the list.

        Edit: we show rpm when cranking, but that doesn't really tell you if the signal is clean.
        Last edited by hybrid; 04-12-2019, 03:58 PM.

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        • #5
          The instructions have all the info you need:

          pf4 coil selection.png

          List of coils given is for coils that have been tested and verified to work fine with Pro-Flo 4. If you keep reading beyond the list you'll see that it says that if not using a coil from this list, that the coil's primary resistance must be at least 0.6 Ohms and inductance must be at least 6.0mH. So yes, if you found a coil that meets these requirements, you can use it. Most ECU's don't drive an inductive coil directly. Most typically either use an external driver or a CDI box. Since Pro-Flo 4 can direct drive an inductive coil, we must keep coil driver current in check thus you can't use coils that are outside our published spec.

          Again, I doubt this is your problem because the result from using a coil that's way out of spec (like a CDI coil) is that the coil drivers on the circuit board inside the ECU typically fail and you get no spark at all. If you still have spark and the engine starts, then you're probably okay and likely have a different issue.

          If you have RPM, then it does mean the signal is clean. Unless you've done something to alter the distributor wiring, the Hall Effect sensor outputs a very, very clean signal and the ECU is very good at filtering signal noise. Signal interference seems to be a common problem with some of our competitor's systems but not with Pro-Flo 4.

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          • #6
            We replaced the plugs, leads and coil (MSD Blaster 2) and everything seems to be OK now - at least for the 30 min test drive.
            I guess maybe the poor GT40 was being over-dwelled by the ECU and overheating or something. It was only about a week old, but clearly was not enjoying life.

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