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

Oh, and when connected MegaTune has all inputs including RPM.

--Alex

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?

Correct.

--Alex

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

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

Damn. Missed the 470ohm resistor from D2 to U5.

Thanks again Joe. :)

--Alex

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?

Could you have 'em wired to both? That sounds bad. I leave 'em on bullet connectors to swap back and forth.

--Alex

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?

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?

Exactly. Swapping. MS currently monitoring only. Soon, I'll swap the injector and coil wires.

--Alex