How to test injector circuit w/ JimStim?

[88tbird2.3t]

I currently have MSII w/ extra 2.0.1 firmware and have been getting noisey Map signals and battery spike's & drops.
Since I'm running low-imp injectors, i followed the following on: http://www.megamanual.com/ms2/V3trouble.htm
Section 16)
If you have MAP sensor spikes that aren't traceable to back-fires, etc, and you are using PWM to limit the current to low impedance injectors, you might have to modify flyback circuit. The fix for this specific problem (noise in the sensor signals, and a noisy +12v battery signal, spikes to 17v, dips to 7v) was to decouple the flyback +12v lines (both TIP125's) from the MS +12v input pin, and run them back to before a noise filter on the +12v input of the MegaSquirt.

To do this, lift the +12v pin of each of the TIP125's in the flyback circuit. The TIP125 are Q9 and Q12 (the ones with the mica insulators). The 12V pin on the TIP 125 is the pin in the middle - melt the solder and pull the pin up with needle nose pliers. Then run a wire from each of the pins you pulled up independently back to the raw +12v supply (outside of the box), and before the noise filter. You can ran the wires through the spares (SPR3 and SPR4, which go to DB37 #5 and #6). 20ga is just fine.

Since I have Spare 4 used up already, I used Spare 3 & 2, which runs into my Eec-IV adapterboard, then jumps to the (2) +12v sources above the proto area.
Started the car after making to mod, and seems like its only running on 1 bank/2 injectors and not really sure how I can test this first without replacing transistors. Car would start up and run fine up till now, now only runs on 2 cylinders.

Now i'm still getting use to figuring everything out on how to use the JimStim, but what I cant understand, is if the +12v to both TIP125's are no longer running through the MS +12v input, because they are jumped to SPR2 & 3 on my MS, how are my injector LEDs firing when I turn my stim on and turn the RPM pots a little? I thought I would have to run +12v jumpers to SPR2 & 3 on the JimStim so that to power the injector circuit? What am I not getting here? I dont think i'm understanding how the Stim is built and working:(

[racingmini_mtl]

The flyback circuit does not provide power to the injector but actually returns power to the battery (which is generated by the injectors when they are turned off). So you don't need to connect the 12V supply to the 2 spare pins because the injector LEDs on the JimStim don't generate a flyback current so there's nothing to return to the battery.

So it will not be possible to test the flyback modification on the JimStim but if the LEDs light up and you make sure you followed the instructions to the letter then you should be fine. Also, make sure all your solders are good, you haven't shorted anything, and that you have continuity between the TIP125 middle pin and your external wiring to the 12V supply.

Jean

[88tbird2.3t]

thanks Jean! I'll check a couple of those things tonight and see what happens

[88tbird2.3t]

would both LEDs light up on the Stim if one of the TIP125's are bad?

I tested both middle leads on Q9 & Q12, and between each lead and its respective prong on the DB37, i get 0.5 ohms, so at least theres a connection
now i'm at the point where i need to take the adapter board out of the car and hook it up to MS to check continuity between the transistor leads and the actual 12v source i have the connected to the the adapter board.

If i still have continuity on each circuit on that point, then i'm guessing I either have a bad TIP, not sure how to check for which one is bad, or one bank has no 12v flyback

If one bank doesnt have 12v flyback, then could that cause the MS to only fire 1 bank and not both?