Spent a few hours on the virtual machine reviewing the Snapon captures of our injector command wires night before. Confirmed a few things, learned some new things, raised some new questions..
Having the breadboard in play between the ECM and FICM on a bench setup works great for creating some situations that would be hard to recreate in a truck. Like FICM having a crank signal, but no injector control wires, at 600RPM. When it was going into limp mode, I could hear the injector solenoids clicking along with a pattern tracking cranks RPM. But they are not actually firing. My little caps are not clicking.. So our FICM is charging and discharging the 2 Injector Power leads in rhythm, every 180°, but the Injector Command wires are never pulling to ground long enough to engage the electromagnet. So who's in charge of this Reset?
First thing we notice in most of my captures below is, I have an electrical issue on Bank A circled in Red. Guessing an injector solenoid on that bank has a poor connection maybe. For some reason it's not draining that power line like Bank B. Will check it out, but it's present in most of these captures.
Above with FICM injectors receiving no command to fire, our Injector Power leads for both banks charge and discharge in a specific crank-timed pattern. As we zoom in below, we can see it's recharge cycles are every 180° per bank, and directly related to the 1st or 16th gap on our ECM created crank speed signal. Which is sent with a 50ms delay from the true crank position signal we can't forget... Some funky math has to be figured in here somewhere. But for now, we will call tooth gap #1 our start of injector charge cycle for Bank B, and every 180° or 30 teeth after that fact with no control inputs,
So I wondered if this circuit cycle switching was linked to crank signal or control wires. I actually did this part last, but for educational sake, will reverse the procedure. Next I started removing control wires one at a time, two at time, and so on to capture how this power switching related to the transformers, was as also related to our Injector Control signals. And it is very much so.. As in, this is our fail-safe, or default recharge time for our PCB coils. If no other input, it uses the crank. If any control input, then it waits for the injector to fire before recharging. Which means, our little FICM processor with the heat sticking to backplane, is probably a busy little fellow making all these decisions..
In this pic we can see how it defaults to our crank based recharge time when just one injector control #4,, is removed from Bank A firing messages. It shifts the time slot to sooner than if would have normally of fired that injector and recharged. So it knew there was not pulse 4 coming, and picked the default trigger time based off the crank..
And here it is again, but with opposite setup. Only Control 1 wire plugged into the FICM. We can see it has no problem Not following the crank speed signal for just one injection cycle per 720° of rotation. So again, the FICM processor is in total control of our operation. It looks at "9" control signals, 8 injector PW / Timing line, and 1 crank signal and does all the calculations. Like our 90° offset, our 50ms offset, and our tooth 1 reference line, to come up with our On Time for each injection cycle.
Betting one could seriously reprogram these units to run just fine with a single Injector Control signal, and that crank input. It's doing all the math, and following set timing rules, while computing all 9 values. With only 1 injection cycle value, PW and timing advance details, this FICM could easily replicate the other 7 injectors based off said data. But at least this way, it gives the ECM complete control over all 8 injectors parameters per rotation. Which means it can balance the injection cycles per stroke, cylinder, or however we see fit. While the FICM works out the injector power control based off simple 8 - 5v On/Off signals. and 1 - 10v crank trigger..
