MS3X V3.57 NA6 Stock – No start, normal cranking, no RPM signal
 

This has been quite a learning process. Once I got past the harness adaptor (https://www.miataturbo.net/megasquir...grounds-81994/), the installation went smooth until first startup. I posted I’ve spent at least 40 hrs searching and reading for possible solutions to my no-start to try to figure it out on my own – I feel I’m at the point where I've extended my own resources and need some help to continue on (I'm much more confident in tuning the car)…

SETUP

• `90 Chassis, stock internal 1.6
• I/H/E, AFM-delete, wired for sequential fuel, stock coils/CAS
• DIYAutotune Pre-assembled MS3X (not PNP) V3.57
• MS3 1.3.4 Release Firmware
• MS2E v3.2.1 MSPNP2-MM9093 base map MegaSquirtPNP by DIYAutoTune.com (in lieu of finding a genuine MS3X 1.6 base map)
• 64-pin DIY adapter connector (MS3/X DB37 to 26- and 22-pin factory harness plugs), wired per Frank’s guide
• Innovate LC-1/XD-16 WBO2

Followed much of the forum and DIYAutotune setup guides for initial MSQ settings, sensor calibrations, etc.

SYMPTOMS
Engine cranks normally, fuel pump operates, confirmed spark present by removing a plug attached to wire while grounded, but will not fire. A couple of backpops through the intake if I prime too much. Composite logs appear to show cam and crank signals but lots of sync loss. And no RPM signal (I understand the engine will not run if it does not see RPM).

• Triple-checked harness adaptor wiring – confirmed 12V at 1B, Main 24 at 2E (CKP in), MS3X 32 at 2G (CMP in), Main 1 at 2C (Sensor GND)
• IAT, CLT, TPS, MAP calibrated and reporting good values
• Adjusted pots R52, R56 (Main) and R11, R32 (X) to output ~2.5V at pin 3 of U7 on each board
• Base timing was/is 14* prior to MS3X (obviously haven’t adjusted base timing yet)

I've attached a Composite Log, I/O and MS3X pins lists, log of cranking, and the .msq of the current tune. Please let me know if there is any other information to provide to help troubleshoot this.

Thanks for the support.

Try reversing the Ignition Input Capture setting.

We have ignition!
 

Much thanks, Matt. Switched Ignition Input Capture from Falling Edge to Rising Edge, fired after some coughs to clear the fuel sitting on the piston tops. I didn't save the Composite Log of cranking after I did this, but sync losses completely stopped, and "RPM SYNCED" was solid ON during cranking, "NOT RPM SYNCED" when ignition ON.

If you don't mind, help me understand why I needed to do this.

The MSPNP and MS3 use different ignition input circuits that require different settings.