90 miata ms3 installed, now no tach - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-14-2014, 03:46 PM   #1
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Default 90 miata ms3 installed, now no tach

i installed an ms3 in my 1.6 miata and after lots of user error i finally got it running, but no instrument tach. i tried a 1k resistor bewteen ig- to 12v and from ig- to gnd at the diag and also a 1k from 2I to 12v and to gnd at the ecu connector... no results. i tried them separately and together.

any other ideas? the only thing i can think of is i had the spark out transistor in backwards in the megasquirt and they possibly went low for sometime while i was trying to figure it all out. i felt the ignitor get very hot, its amazing i didnt blow up my coils and that the car is running great. but, did it fry the tach out circuit in the ignitor? did it fry the tach?

i have an o-scope i can put on it, its just so hard to see outside in the bright light and its big with no stand.

details in build thread start around page 5
https://www.miataturbo.net/build-thr...4-74776/page5/
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Old 07-14-2014, 03:49 PM   #2
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edit: nevermind, I misunderstooD
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Old 07-14-2014, 04:03 PM   #3
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try ig- to b+ through a 1K resistor again.
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Old 07-14-2014, 05:14 PM   #4
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i had the resistor just stuck in the pins prior, this time i crimped on some spades so im sure it has good contact. still nothing. i verified continuity from the ignitor connector to the resitsor lead itslef and it checked out good. resistor measures 998, i tried another anyway. still no tach.

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Old 07-14-2014, 05:31 PM   #5
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i guess it wont work so long as you fubared your ignitor.
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Old 07-14-2014, 05:54 PM   #6
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i guess ill be dragging the oscope out there. anyone know what the signal looks like. 12v square wave?
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Old 07-14-2014, 07:30 PM   #7
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does ig- goes straight to ground if you test for continuity?
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Old 07-14-2014, 08:02 PM   #8
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with everything plugged in 1.5K from ig- to ground at the diag connector. i unplugged the ignitor and measured 2.56M between pins D and F.
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Old 07-15-2014, 06:40 PM   #9
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so im lead to bvelieve those are good numbers. ill get the scope on it next time i have a chance, to see what if anything, its outputing.
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Old 09-12-2014, 11:48 PM   #10
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i forgot to update this. so for future reference:

this is what i had on the scope. never mind the fact that its absolute garbage, and didnt change frequency with change in rpm, its also only about 0.9V P-P. my scope could not hold a trigger on it, which tells me it was scattering.





i grabbed a used ignitor from ebay for $30, and...











so an ignitor can just have the tach circuit go bad, and still measure ok.
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