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No tach ms2pnp

 
Old 11-28-2015, 11:00 PM
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Default No tach ms2pnp

I have a 1991 with a 1994 turbo motor. I can't get a tach signal. I tried the resistor trick in the dignostic port and still nothing. What am I doing wrong lol
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Old 11-29-2015, 05:08 PM
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No tach in tunerstudio or dash?
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Old 11-29-2015, 06:38 PM
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Which coils are you using. 94? Or 91? Do they have 3 wires or 4?
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Old 11-30-2015, 12:11 AM
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I'm useing all 91 electornics so 3 wire and on the dash.
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Old 11-30-2015, 12:22 AM
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What did you jump in the diag box.
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Old 11-30-2015, 09:02 AM
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you did the resistor wrong, or you fubared your ignitor.
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Old 11-30-2015, 02:13 PM
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I did the IG- to B+ with a 1/4w 1K resistor. And I've got a brand new igniter.
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Old 11-30-2015, 02:15 PM
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Old 11-30-2015, 02:22 PM
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I read though that. Was slightly confused though. I'm not running cops.
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Old 11-30-2015, 02:25 PM
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What should my tachoutput be in mega squirt?
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Old 11-30-2015, 02:28 PM
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Off.

Wait, if you are still running 1.6 coils and everything the tach should never have broken.

Dead fuse is my guess.
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Old 11-30-2015, 02:32 PM
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Oh ok I'll start checking fuses.
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Old 11-30-2015, 02:35 PM
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Do you have 12v at B+?
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Old 11-30-2015, 02:51 PM
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i wrote a huge reply and lost it explaining why the resistor works and why the tach goes dead when you pull out stock ecu, even though the 90-94.5's tach is driven through coils.

i dont feel like writing it again right now. :(
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Old 11-30-2015, 02:54 PM
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Now I want to know...even on 90-93 with the ignitor?
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Old 11-30-2015, 02:57 PM
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Dang that sucks Brain. Can u sum it up. It's just weird driving the car with no tach lol it's not a fuse.
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Old 11-30-2015, 03:12 PM
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Why does the tach go dead with the megasquirt?
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Old 11-30-2015, 03:17 PM
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because the stock ecu provided the pullup to power the tach signal.

the coils go to ground with each spark event.

the signal must have voltage to start with.

when coils ground, the tach sees constant voltage, then none -- the rate it sees those events is how it knows the engine speed.


1K from B+ (12v) to the tach signal (IG-) puts power back on the wire. otherwise there's no activity on the wire, cause youre going from no voltage to ground -- no signal.
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Old 11-30-2015, 03:20 PM
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Very nice. Thank you brain. I now understand it better. My megasquirt is set to tachoutput should it be off with the resister in place?
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Old 11-30-2015, 04:11 PM
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I don't think the mspnp's even have tach output hooked up. Or at least the jumper shouldnt be set. Adding the resistor is emulating the stock ecu. If adding the resistor isn't working you have bigger problems.
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