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Thread: Intermittent RPM Signal

  1. #1

    Default Intermittent RPM Signal

    Hi all. 427 Ford V8, MSD magnetic pickup distributor (8578) with a MSD Blaster SS coil. Borla stacked injection.
    Software version 2.2.0, build 4, Firmware version 1589.

    Here's the VR magnetic pickup at the ECU:
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    Looks nice & clean.

    Yet here's the output from the ECU on the white points wire to the MSD box:
    Click image for larger version. 

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    Very erratic and loads of pulses missing.

    Here's the ignition parameter setup in the EFI software.

    At the cranking speed (about 150 RPM), there should be about 8 pulses per second. Distributor magnetic pickup signal is perfect. But output from the ECU to MSD box is far from perfect!

    Can anybody give me a direction to go here? I know all the arguments between Hall-Effect & magnetic pickup, but the customer wants me to go the magnetic route.
    I can't see a reason why the points output is so erratic. HELP! Andy.
    Click image for larger version. 

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  2. #2

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    All powers, grounds load tested. Perfect. Can see no other software parameter that can be causing this. May have no choice, but to call ECU on this one. Unfortunately, Holley techs are not replying to any emails about this. And it's been two weeks plus. If anyone has any ideas, throw them in, otherwise it's ECU replacement time. Desperate times. Andy.

  3. #3

    Default

    If you know anyone else with a HP ECU, then try the swap to see if it changes anything. Could be a bunch of tricky to find things such as a bad harness, bent pin somewhere, some sort of programming error in your tune, etc.

  4. #4

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    This problem sounds similar to another member is having with his Sniper where there is no spark with timing control enabled. Looking at your waveform, those humps are most likely the effect of starter current. And when the signal did pull to ground, the voltage was OK. You could perform a bypass test with a test light connected to ground a touch on and off the white points wire, to simulate the ECU trigger signal and see if the CD box fires the coil.

  5. #5

    Default

    Thanks for the reply. Already did the test light pulling to ground on the white wire. Perfect spark. You are correct in saying that the oscillations are caused by starter voltage drop. Unfortunately, you're not correct about the switching. I can zoom in using Pico software and the pulse width varies too much. We're in the UK and these ECUs are scarce over here! I've sent Holley the tune, but they are not responding. But good suggestions anyway, thank you. Looks like we may be going dual sync distributor first, then another ECU if no luck. Prestige Motorsports did the tune with the engine on their dyno, then shipped over the pond. Must say they've been amazing. Will keep you all informed. Andy

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