Ok, I think I am narrowing in on an issue that has prevented me from running megasquirt like 4 months ago. My initial problem was that after gettign megasquirt running, the tach signal would spike and it eventually died to never return again for the megasquirt. However it has been running fine on the stock ecu so i figured it had to be the megasquirt and so i bought another kit, built it very very carefully ... but it just wont pick up RPM. So i did some testing on the car with a multimeter and a spare CAS and here is what I found out:
Testing the connector with no sensor, both cars read 12v for white/red, and 5v for ckp/cmp wires so there should be no difference there.
When hooked up to my red 90 and using the blk/ltgrn wire for a ground:
White/red is 12v
white (ckp) is nothing, but shows a little tiny bit of voltage when the wheel is spun by hand
Yel/blu operates as expected and outputs either 0 or 5 volts depending on wheel orientation
Then I hooked up the sensor to my 97 to see if the sensor acted the same, but this time the White wire operated as it should and gave me 0 or 5 volts.
So Finally I am left with this question, what can I do to fix this? is there a possibility of it being more complex than simply the wire is grounding itself out somewhere? Perhaps I will try running a separate wire to see if that does it.