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Old 05-01-2009, 09:53 PM   #1
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Default No start w/ MS Parallel

Just built my MS again. Now I have a no start. Figures I'd ask here while I troubleshoot myself.

With the MS attached to sensors only I get a crank no start. If I disconnect only the shielded tach signal wire, it starts no issue.

MS is in parallel w/ stock ECU. The harness in the car is the same that I've been using for a while. I've checked all pins to ground, re-cleaned the PCB, and went over my tach input wiring. Still looking....

--Alex
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Old 05-01-2009, 09:55 PM   #2
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Oh, and when connected MegaTune has all inputs including RPM.

--Alex
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Old 05-01-2009, 09:55 PM   #3
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I'm confused.

If you disconnect the tach wire from the MS, and the car runs, this means that the injectors and ignition is still connected to the stock ECU, yes?
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Old 05-01-2009, 10:00 PM   #4
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Correct.

--Alex
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Old 05-01-2009, 10:03 PM   #5
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Just rung out from the shielded input pin 24 to the opto isolator. Resistance is good, and open to grd.

TACHSELECT to OPTOIN is jumpered. D1 and D2 are jumpered. C12 and C30 are not installed.

-Alex
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Old 05-01-2009, 10:07 PM   #6
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So it doesn't seem the signal is being grounded in the MS. But how else could I loose the stock ECU when MS is plugged in? I'm a bit lost.

--Alex
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Old 05-01-2009, 10:14 PM   #7
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Damn. Missed the 470ohm resistor from D2 to U5.

Thanks again Joe.

--Alex
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Old 05-01-2009, 10:17 PM   #8
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Ok. Not sure how I helped, but you're welcome.

I'm unclear as to whether you have the injectors and ignition wired to both the MS and the stock ECU at the same time, or are you swapping the wires back and forth?
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Old 05-01-2009, 10:18 PM   #9
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Could you have 'em wired to both? That sounds bad. I leave 'em on bullet connectors to swap back and forth.

--Alex
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Old 05-01-2009, 10:19 PM   #10
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You're making my head hurt.

Yes, it would be bad. Do I assume correctly that you do have them bulleted, and are swapping them back and forth?
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Old 05-01-2009, 10:20 PM   #11
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Sounds like he was running the car off the stock ecu for now but had the MS connected for monitoring to make sure all systsems were go, meaning all gauges including tach were working before switching spark and fuel over to MS?
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Old 05-01-2009, 10:22 PM   #12
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Exactly. Swapping. MS currently monitoring only. Soon, I'll swap the injector and coil wires.

--Alex
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