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Getting tach working after COP ignition install

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Getting tach working after COP ignition install

Old 02-20-2014, 02:42 PM
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Default Getting tach working after COP ignition install

I recently installed the Fab9 coil-on-plug ignition system into my 1995 running a JR supercharger and a Link and I'd appreciate some help getting the tach needle working again. The engine runs like a champ in this configuration. There's just no tach needle movement. The Fab9 people warned me that the tach could stop working because the needle runs off a signal from the original coil, which is obviously no longer there, so I was kinda expecting this.

I've been working with Brandon at Flyin Miata on this, who suggested moving the b/w wire from 2I pin to the 1F pin. The logic is that 2I is connected to the needle and 1F drives a 12V tach output from the Link.

I made that change and was successful in getting the tach needle to move properly again. The problem is that the engine either idles at 2200 rpm, or not at all. That is to say, if I rev up the engine and then take my foot off the throttle, the idle will rest at 2200 rpm. In past situations where the engine occasionally idles too high, I would tap the throttle and the idle will drop back to normal. But when I attempt this with the new wiring configuration, the engine will die immediately. It'll restart once I crank over the engine, but it still won't idle properly.

I've verified that the engine runs perfectly if I remove the wire from the 1F pin and then dies again when I reconnect it, so clearly there's something going on with that configuration. Flyin Miata is continuing to investigate the situation but I wanted to see if anybody else had an idea.

I've heard about using a 1K resistor to jump IG- to B+ in the diagnostics box to get the tach working, but it seems like this would only apply to a stock ECU. Is that right?

Much thanks in advance...
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Old 04-09-2014, 06:31 AM
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You ever get it worked out ?
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Old 04-09-2014, 11:15 AM
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Well, kinda. I removed the kit since I couldn't get it working quite right. I had a couple failures in the ignition module that left me stranded. The system ran great when it was working, but it got to the point where it wasn't much fun anymore. Bryan (the Fab9 owner) was great to work with but we simply couldn't keep the ignition going for me.

Before I removed the system, Bryan was describing a tach adapter from AutoMeter that would drive the gauge. It's not very expensive and it's easy to install so that seems like a reasonable option for anybody in a similar situation. I hope and expect you'll have better luck than I did with the system.
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