1992 Miata No Start
 

Hello! I have a 1992 Miata and I just finished building and turboing it. I made the mistake of doing everything at once, causing a no start. I have looked at many no start threads, but I cannot seem to find my problem. I currently have a DIYPNP Megasquirt in the car, and I believe everything is running fine. The problem I believe is causing the no start is that the ecu is not receiving a CAS signal. When I took the car apart, everything was working fine. I have rewired straight from the CAS plug, to the ecu to eliminate that being a problem. I have also tried putting in a different cas from a 1996 miata. I got this from a junkyard. I am not positive that this worked, but it said that the car ran and drove. The stock ecu doesn’t start the car anymore either. I am not really sure what to do anymore, and I have already taken it to another shop to see if they could find the problem, and they were not able to. I was able to create a composite log a while ago, but for some reason I cannot anymore. Here a data log and the composite log from about a month ago. Thanks in advance!!

Really need your .msq file as well. I can see yeap, no RPM there in the MSL - and you must be really close to sea level with 116kpa.

Nope at about 6,000 ft. lol. Not sure how to fix that, I noticed that as well. Here is the tune file.

Nothing there looks obviously wrong - other than fixed timing - but if you haven't timed the car yet, eh, no biggy. A composite log would definitely help - so would making sure you have 12v on the w/r wire on the cas and ground is.. well, grounding. You can also take your old CAS, plug it in, and spin it with a drill - see if you get any sign of life from the composite log there as well.

Here is the composite log file from a while ago. I am pretty sure I am getting 12v on the w/r wire, will double check tomorrow. I don't know if you know a lot about the DIYPNP, but I unbolted the CAS and spun it by hand with the key on. The voltage at OP- should go from about 12 volts to 0 and back again 4 times per revolution. and the voltage at VR2 should go from 5 to 0 and back again 2 times per revolution. When I had the multimeter connected to OP-, I was getting a constant 1.2v. (Extremely low). When I spun it, the voltage would drop very close to 0. It did not matter if I spun it 4 times or half a rotation. When connected to VR2, it was doing the same thing but getting a constant 4.5v.

If your MAP sensor is reading 116kpa at 6k feet, something is definitely wrong. Either you have the wrong sensor selected in your config, or your sensor has failed. I'd fix that first and foremost. I live at 7k feet and see about 79kpa ambient, so I'd expect to see somewhere in the 80's for you. If the map sensor is off, then everything is going to be off with your tune.

Actually I just realized something - in your log I can see where you're cranking - the voltage drops to 9-ish volts - but your MAP doesn't move at all. Now, 116kpa is high - but there's a plethora of reasons to explain that, none of which solve the immediate problem of no RPM signal. However, while you're cranking, I don't see it drop at all. I'm wondering if your timing belt is broken. It could be that the map line isn't hooked up - but timing belt is a 2-for-1'er. You can look at the cam through the oil cap while someone turns it over.

Edit: and your coolant is 180 degrees. And your AFR is reading 10.1-14.4 - that should be around 22 if your wideband is set up correctly. Wondering if the firmware is on the fritz and needs a reflash, along with a sensor recalibration. Curious.

I don't think the timing belt is broken. I just replaced it with a brand new one, and have the front timing belt cover off so you are able to see it.

Could swap the OEM ecu in and see what happens.
https://cimg7.ibsrv.net/gimg/www.mia...d6af905ea6.gif

Stock ecu doesn't start the car anymore either.

Post a video of it cranking, taken from a decent phone camera. Aka borrow your friends phone if you have an iPhone 4s...

Here’s the video

Something sounds seriously mechanically wrong. Like no Compression in 2-3 cylinders. Do a quick compression check maybe?

edit: eh listened to it again maybe it’s not too bad...

Yeah I didn’t think it sounded too bad.

How is coolant 180 degrees if the car is just sitting there and its it's ~30 degrees? Wideband is set up, but the sensor is not in the exhaust as I currently do not have a downpipe. Shouldn't cause the car to not start you wouldn't thing though.

Like I said - it's weird. It's also reading your air temperature at 70. Something appears to be uber-f'd. I'd suggest getting an old priest and a young priest - or reflashing the firmware.
https://cimg9.ibsrv.net/gimg/www.mia...c1bb9d89c9.png

Alright I’ll try doing that then let you know how it goes. Thank you.

Air Temp is still 70, but at least the coolant is 54-ish and showing some change. Still don't see any inklings reading an RPM though - SGT might be the root though.

How can I fix that?