Crank/No Start; RPM Detection Issue
 

Need help figuring out what the hell is going on. Megasquirt PNP2 v1.2 90-93 3.2.1, recently turned the car on to give a run, and its cranking but not starting. When it first happened, the MS would also power cycle itself twice in about 5 second intervals. In tuner studio, I get an error along the lines of "argument between ignition output and spare outputs". Going into Output Port Settings and disabling PM4 gets rid of the error, but the car would still not start. When I begin to crank, the RPM dial in Tuner Studio goes to 1, then stays there until I power cycle the MS. Reflashing and loading a base map does not change anything, except I have to go back into Output Port Settings and disable PM4 after loading the base map. I've never had to do this before, and I don't know why I have to do this now.

Ive Attached a log of a five second start attempt on the base map available on megasquirtpnp.com.

Does this sound like a hardware issue or a settings/software/firmware issue?

I should also mention I've tried switching out the Camshaft Position Sensor with a spare I had lying around.

Update on the situation. I was able to get an RPM signal and spark output by switching the Ignition Input Capture to "Rising Edge", as opposed to "Falling Edge" as set in the base tune. The signal wasn't very stable though, and seemed to reset back to 0 RPM after every ignition event. Its my understanding that events may be captured by either method, but my set up prefers falling edge to run properly, as noted in DIY Auto Tune's article "How to MegaSquirt Your Mazda Miata", as well as the info panel in Tuner Studio when selecting the question mark next to the Ignition Input Capture option. This leads me to think there may be an issue with whatever circuitry picks up the falling edge signal, if its different to what picks up a rising edge signal. I will do some research and see if I can obtain some relevant circuit diagrams.

Please post up your tune file and a composite log of an attempted start.

This is a log of me cranking with rising edge, and the tune file to go with it. A log using the downloaded base tune is attached to the original comment.

need a composite log, click on the diagnostics tab, hit save to file, and crank for a good 20 seconds or so to ensure a reading.

Sorry, this has been established with Matt over email, but I forgot to update the thread. Here they are.

Any update on this? I think I'm having a similar problem.

Noise filter?

Issue resolved. Was caused by corrupt firmware. I eventually flashed using the firmware wizard in Tuner Studio as opposed to the "boot jumper" technique, and that got it running properly. Idk why using the boot jumper technique didn't work for me, but I believe those with a similar issue as this in the future aught to try reflashing using the flash wizard in Tuner Studio if they haven't already.

My issue was also fixed by reflashing the firmware using the wizard in TS. I also needed to switch from falling edge to rising edge under ignition input capture to get the car to start reliably.