Everything points to either a bad starter or bad battery especially from the low voltage I see in the logs, but both have been checked and swapped out for different ones with the same problem persisting.
I have a 1995 miata, MSPNP2 with EV14 650cc injectors and a BEGi Gt2554 turbo kit installed. Over the past few weeks my cold starts have gotten progressively more difficult. I had to use a jumpbox to be able to get the starter to spin enough to get it to catch on the first start of the day, but it will take 10-15 start attempts to even get it to start thinking about catching. Hot starts it will fire right up.
Now I can't even get it to start when I have it hooked up through jumper cables to another car. I switched the battery out with a know good one from my dads miata thinking that was the issue, but the starter is still very sluggish. It constantly acts like the battery is really low, even on jumper cables to another car, the extra juice doesn't change the results. I have double checked the wires at the starter and I get 12v there when I turn the key.
It'll crank for about 1.5 seconds at most before it stops and just clicks the solenoid. Bad starter right? I replaced the starter today with a refurb from napa auto parts. Went to start the car and nothing has changed. It still spins very sluggishly and wont start. I double checked for spark and I have it, I did hear it explode a single cylinder thru the exhaust once or twice, so I think if I can get the starter to spin up normally it will catch eventually.
Bad ground maybe? I used a thick jumper cable directly from the negative battery terminal to the block... no difference.
Bad hot lead from battery to starter? It gives 12v when checked with a meter, we did attempt to jump the starter on the car directly from a battery, got it to spin but the solenoid wouldn't extend out into the fly wheel.
Correct me if I'm wrong, I don't believe the ignition switch or the clutch switch wouldn't be the culprit in this case as I do have 12v at the starter when the key is turned.
I will pull the starter back out tomorrow to return it for another and run some tests on it before we try to re install it.
Anecdotally, when I was farting around with my ECU in between start attempts I did manage to corrupt the firmware and brick my megasqurt temporarily. While the ECU was bricked without a tune I was able to spin the starter much faster and longer than when a tune is loaded into it. In my mind with the tune it's as if the cylinders are getting loaded up with unburnt fuel somehow and the starter is having a hard time pushing through the extra compression.
I had to update the firmware into the MSPNP2 to bring it back to life. I reloaded my old known working tune back onto the new firmware. I have also tried different .msq files provided by diyautotune with no difference in the starter dragging.
I noticed when I look at the logs of my start attempts that the voltage will drop significantly during the start attempts, 6.4 volts at it's lowest and the engine makes it up to a peak of only 242rpm now. The logs of start attempts before the ECU firmware corruption had the rpm going as high as 689rpm.
Start attempt a few days ago: