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Thread: A little stuck getting started

  1. #1
    Electronic Ignition!
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    A little stuck getting started

    I have a '91 TBI 350 with the 1227747and ARJT chip that I am swapping into my '69 GMC. I have modified the harness (which is why I'm here LOL), and have tried to fire it up. The issue that I'm having is that I'm not getting an injector pulse. I know there are several posts about causes for that, and I've been through all of them and everything checks out. So, what I wanted to do is to hook up to the ECM to scan and see what I could be missing. I really need to figure out whether this is a wiring issue, or an ECM issue. My issue is that when I hook up to the ECM, I'm not getting any readings. Attached are a couple of screenshots of what I'm seeing (winALDL & putty). Just looking for some advice on what to check next.


    2017-03-18_1607.png
    2017-03-19_0726.png
    Last edited by mjensen; 1 Week Ago at 09:05 AM. Reason: fixed ECM model

  2. #2
    Fuel Injected! mmigacz's Avatar
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    Are you using a TBI distributor (Or a TBI ignition module)?
    1986 ski centurion boat, 351W, gt40P heads, edelbrock performer rpm, 1227747 ecm, 72 lb/hr injectors (@18 PSI fuel pressure), .490/.490 lift, intake 278 duration, exhuast 282 duration, 112 lobe separation

    1969 camaro, 355ci, performer RPM intake, camel hump heads, 1227747 ecm, 454 throttle body (@18 PSI fuel pressure),

    2016 Chevy Cruz

    2014 Chevy Silverado

  3. #3
    Electronic Ignition!
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    It's using the stock TBI distributor that was in the Blazer.

  4. #4
    Super Moderator Six_Shooter's Avatar
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    I'd download Tuner Pro along with the correct ADX for your application and use that.

    WinALDL seems to be hit or miss as far as getting good data.

    And do you mean 1227747?

    Do you have spark?

    Does the fuel pump prime, and does it turn back on when cranking with the OPSU (Oil pressure Sending Unit) unplugged?
    The man who says something is impossible, is usually interrupted by the man doing it.

  5. #5
    Electronic Ignition!
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    Haha...Oops yes. I have Tuner Pro RT, and it's not pulling any data either.

    I have spark (it will run when spraying carb cleaner)
    All relays kick on (fuel pump runs while cranking) - I have not tried with the OPSU unplugged
    Noid light on the injector harness indicates no signal from ECM
    Replaced Ignition module
    Traced every wire (found some issues and corrected)
    Tested all voltages and resistance through the wires

    This is why I was hoping to scan the computer to see what signal I could be missing, but I can't seem to get any of them to work. I'm starting to wonder if the ECM could be bad?
    Last edited by mjensen; 1 Week Ago at 09:08 AM.

  6. #6
    Fuel Injected! mmigacz's Avatar
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    There are two wires going to each injector. The white and red wires should have 12V all the time when the ignition is on. Can you confirm this? The ECM creates the pulse by providing a ground (blue and green wires) to the injector.

    lf you unplug the injector and put a nine volt battery across both terminals, you should hear it click. If you try this, only do it for a fraction of a second.
    Last edited by mmigacz; 1 Week Ago at 11:56 AM.
    1986 ski centurion boat, 351W, gt40P heads, edelbrock performer rpm, 1227747 ecm, 72 lb/hr injectors (@18 PSI fuel pressure), .490/.490 lift, intake 278 duration, exhuast 282 duration, 112 lobe separation

    1969 camaro, 355ci, performer RPM intake, camel hump heads, 1227747 ecm, 454 throttle body (@18 PSI fuel pressure),

    2016 Chevy Cruz

    2014 Chevy Silverado

  7. #7
    Electronic Ignition!
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    I have verified that they have 12v and the injectors do click with a 9v battery. I've checked the resistance in the injectors, as well as the wires running to the injectors, and they are well within spec.

  8. #8
    Fuel Injected! uncabob's Avatar
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    Dumb question, but have you verified fuel is actually getting up to the injectors?
    Don't force it, get a bigger hammer!

  9. #9
    Electronic Ignition!
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    I have, and we've got fuel. I'm fairly certain that the computer is just not receiving SOMETHING that it needs in order to tell the injector circuit to ground.

  10. #10
    Electronic Ignition!
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    Well, now I can't even get the software to connect to the computer. I'm taking tomorrow off, so I'm going to run over to the local junk yard and pick up another computer. I'm just convinced that I've somehow screwed this one up.

  11. #11
    Electronic Ignition!
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    Picked up a new ECM and harness from said truck. EXACT SAME ISSUE!!! So, let me ask. Can a faulty oil pressure switch, or no oil pressure cause the injectors not to pulse?

  12. #12
    Fuel Injected! jim_in_dorris's Avatar
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    when cranking, the oil pressure switch isn't used. I ran my truck for years without the oil pressure switch being connected. D14 and D16 from the ECM are what control the injectors A and B. Check for a crank signal on C9. that is what the ECM uses until the engine RPM's reach a running state. You may need an O scope.
    Last edited by jim_in_dorris; 6 Days Ago at 09:56 PM.
    Square body stepsides forever!!!

  13. #13
    Electronic Ignition!
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    Thank you for your response! That is very helpful to know. One question about the crank signal. Where should the source be coming from? Is it different between a '91 and a '94? The only constant in all my tinkering has been the distributor, as an fyi. Maybe the issue is related to that (I have replaced the ignition module)

  14. #14
    Electronic Ignition!
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    Got it figured out! When I put the new harness in, I failed to hook up the 12V supply to the injectors...doh!

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