slpin

iTrader: (9)

ok... i know i wired it correctly, i bought the megasquirt 2.2 from diyautotune.com

the problem is, i cant get the megasquit to regonize rpm signal and squirt fuel. but i know the ECU is firing and the factory tach moves.

if i pour some gas into the port, i can get it to sputter.

the megasquirt would always read 0rpm.

any ideas?

i hooked it up to the same RPM signal that the AFC/whatever uses
and i also tried hooking it up to the VE-, and both would not work.

renns

Sounds like you are wiring up in piggyback fashion, with stock ecu firing the plugs? I'm not certain where the AFC/whatever gets its tach signal, but if you are getting no reading now you either have an incompatible signal, or a wiring error. Triple-check the wiring for shorts and opens. If it checks out OK, then you can either figure out how to adapt the MS to accept that tach signal (details here: http://www.megasquirt.info/v22manual/mwire.htm#ignition), or choose an alternate tach signal soruce. I ran my first FC install from the -ve terminal of one of the coils. If you use leading, configure as 4-cylinder, if trailing, 2-cylinder.

slpin

iTrader: (9)

I know it is not the wiring. I made my harness, that didnt work - and then I bought a harness, and that didnt work either.
I tried the RPM signal, which is the fourth wire from the left on the S5, 3 wires down from the 12V IGN hot

and then i tried the VE- one that is also on the harness. that one should connect to the leading.

it is not reading rpm at all - while my tach is bouncing, the megasquirt tach stays at 0.

renns

Sounds like you are hooking to the 5v signal line to the coilpacks? The stock tach circuit will not operate at that voltage level without modification. Take a look at the schematic on the link I sent you. See the diode labelled 'D8' with the name John beneath it? It's a zener type diode, which effectively blocks low-voltage signals from the circuit. This helps avoid false-triggers on many installations, but is likely preventing any triggering in your install. You could try jumpering that zener and re-testing, or just run a wire to the coilpack as mentioned previously.

slpin

iTrader: (9)

i am not sure. i looked at the link and i seemed to have it wired like that.
the VE- is on a pin on the ecu wiring harness, and that is the one i tapped to.
do i need to run a wire directly from engine bay to megasquirt and tap a different one? i thought they were the same as it is labeled VE- on the ecu wirign harness. can i have a picture of where you tapped yours if its not too much to ask?

renns

On my S4 install I didn't cut into the stock harness at all. I modified a stock ecu to get the required sensor signals, and ran a separate wire from the coil back to the MS for tach signal. Take a look at the coilpack. The coil itself has two small electrical connection studs. There are '+' and '-' markings molded right into the plastic of the coil body. Simply connect a wire from the '-' side, and run it back to the MS for a tach signal. It's best to run a shielded wire for this run, although many have got away without it.

slpin

iTrader: (9)

i see.
alright, i will give it a try on friday and let you know

thank you for your help.

jayroc

I used a FC coilpack and got my signal wire from the stray wire coming off the leading coil pack, not the +\- connector. I don't think they do anything except diagnostics maybe?
Anyways, I used unshielded wire and a 10k resistor in line with and got a real stable RPM input from that.

renns

Was that the extra tach line? I tried that, and it worked fine but then the in-dash tach read zero. Never tried the series resistor, as I was up by the coilpack already anyways...

jayroc

That's weird, I thought FCs used trailing as well for tach input.. Honestly, I don't know what stock purpose that wire serves.. I think it is disconnected on a stock setup? I am using the coilpack on a FB with a special ignition circuit and that wire works quite well as a MS ignition source, with the resistor in line that is.
I think it was Mike Robert that told me the trick with the potentiometer in series to find the correct value resistor, other folks' mileage may vary..

slpin

iTrader: (9)

im using the black round connector thingy that goes nowhere on the coil
it seems to work....

Rex4Life

Yea that's what I'm using right now, it's a female bullet connector right.

On the S4 turbo schematic it's F-39 check connector--a yellow/blue wire.