Megatune RPMs?
 

So i hooked up the megasquirt to my 90 miata and when i turn the car on without trying to start it, megatune sees all the sensors except the RPM. I tried to start the car and still no RPM. Right now it doesn't work. I think I may have to check the miata specific mods on the board again, but i'm sure i did this part correct. Any thoughts as to what it may be?

I'm using the harness that i purchased from braineack, so i hope thats not it.

Ok, I rechecked all the mods for the MS to work with the miata and everything checks out. I used an mulitmeter to check all the resistance values and it all checks out.

I used the multi-meter to measure voltages coming from the CAS and i only get 2.5 volts. Is this correct? I thought it was supposed to be 5V. Am I wrong? I'm just not seeing any RPMs in Megatune, so this makes me believe that either my CAS is not working correctly or something is wrong with my MS. Maybe i'm missing components? I checked everything and compared it with Braineacks DIY sticky and all the components are there.

This is what happens when i turn the car to the on position without starting it

1. The fuel pump turns out for a little while
2. The two outer LED's on the MS are on

Megatune
1. all gauges are white except for the RPM, AFR, and pulse width 1
2. all other sensors are giving readings


This is what happens when i try to start the car

1. Engine cranks and cranks and cranks, like i have no spark at all

Megatune
1. RPM gauge is still red
2. Map sensor is showing approx. 85-90 kpa (normal is 99kpa without cranking, sea level)
3. IAT is showing ambient air temp
4. Coolant is close to ambient.

This leads me to believe that i'm not getting an RPM signal therefore it won't spark.

HELP ME DIAGNOSE THIS!! ITS DRIVING ME CRAZY.

What steps should I take to diagnose this problem.

Everything runs perfectly on the OEM ECU, so I don't think the CAS is a problem.....

That's exactly why it won't start, without a tach signal it won't spark.
What MSQ are you using? Can you zip it and post it in a thread.
Make sure you have your decoder settings setup right.
Double check the harness to make sure it's tapped correctly, though I'm sure Scott did it right.

I used the MSPNP 90-93 MSQ and modified that to match that of the DIY autotune install pages spark settings. Used the correct coil settings for it.

check the ignitor, and or your spark wiring.

you're certain the tach input mod was done correctly on the MS board itself?

other than that make sure you have MSnSe setup correctly.


the tach signal itself is the thick gray signal wire on the harness. double check it's on 2E, in between the blue/white and two black ground wires. make sure there's no way the shield is making contact with the signal wire itself.

Check what decoder settings you have setup for tach input.

Have you put jumpers between XG1 and XG2, OPTOIN and TACHSELECT, TSEL and OPTOOUT.

Without these you will not receive spark in MS.

Awww snap!! Got my biatch runnin on the MS!! Turns out that one of the jumpers wasn't soldered on, therefore it just fell out. Guess i forgot to do that!! That was a stupid mistake. Now I know to quadruple check my work. When i fixed that it still wouldn't start, it would backfire instead. Turns out that the wiring harness had the coils reversed. Ha Ha

Now to tune......You guys will be hearing from me soon!!

Thanks for your posts, it made me check all the tach mods over and over again until I found it. What a relief.....