1999 stock motor no turbo (yet)
MSPNP2
Force Flow 640cc injectors

I've had megasquirt installed for about 2 weeks now and I've been driving and tuning it. I finally felt confident enough to install the injectors I had bought in anticipation of my turbo getting here. Yesterday (merry Christmas btw) I installed the Force Flow 640cc injectors and made the adjustments in tunerstudio that FF's website told me to (req fuel, dead times, and voltage correction). After doing that, the car started fine and I began to tune my VE tables again for the new injectors. My focus at the time was to fix a heat soak issue I'd been experiencing at idle (AFR would get leaner and leaner as stock NB IAT sensor reading went up and peaked at around 150F). I never got to fix that issue because the car decided to stop starting.
This morning I began tuning again, and the car started from a "cold" Texas December start at 70F, and I got some VE tuning accomplished, but after taking breaks the car hasn't started since.

I've gone through https://www.diyautotune.com/support/...tartup-tuning/ and done everything they said to do with no results. Especially cranking pulse %, I've been messing with that for 3 hours now. I've messed with the req fuel number going all the way from 4.0 up to around 8.0 (currently set to 5.6). I even went so far as to re-download a base map for my 1999 and start from scratch. So far all I keep seeing while cranking is the car goes up to 230ish RPM and won't run at all. The best result I've had all night is one single ignition take place that bumped the RPM up to around 320 for a second, but other than that not a thing. I even used a timing light to verify that I was getting spark at 10deg.

Logically thinking, cars need air, fuel, and spark to run. If it WAS starting until I messed with fuel, and now it won't start, then the only thing that can possibly be wrong is fuel. And I don't know if the engine is getting any fuel at all to be honest. When I pulled a spark plug, it was dry and didn't smell like fuel at all in the engine, I also don't hear the fuel pump running when I turn the key to "on" so maybe the pump decided to pick today of all days to die on me. I swapped the fuse as just a quick check with no success. It's late now though for me so I'm going to bed. I'll troubleshoot for a possible fuel system failure tomorrow. For now though, I attached the last tune where the car managed to start and a log file of me attempting to start it with that tune (I even did a flood clear in the middle of the tune to demonstrate that I haven't just been flooded this whole time).

Hopefully its a software issue and I didn't break anything.

 

Lies.

 

ugh. see my signature. It's just how I am

...it would help if MT.net didn't log me out every 3 minutes

 

Why you do dis? What basemap are you using?

 

MegaSquirtPNP by DIYAutoTune.com
1999-2000 v3.3.1a
I know it's not the same firmware but it was working for a while. I just confirmed those settings you screenshotted looked the same as what was in the base tune too. What settings should I start with?

 

I have no idea why anyone would run anything other than sequential on an NB. Not your primary issue though.

I would use test mode to confirm your pump isn't being triggered by your megasquirt. Then grab a DMM and start checking for power. I had the bulkhead connector fail on mine a couple months ago.

 

So the car managed to start this morning, and I did the test mode thing you suggested. It is able to be controlled by megasquirt. So idk why it decided not to run the other day. Maybe excessive heat soak caused a relay failure or something like that, idk if the fuel system relay is in the engine bay or not. Temps reached up to 170 in the engine bay. I'm tuning idle stuff with an open hood from now on. It did have some trouble starting while I was running errands, but I just bumped up the fuel in cranking pulse and it seemed to help a lot. I'll post again if I continue to have issues.

 

Okay. So I had the issue again. But I think I managed to track down the cause. MAYBE.

I did research and found that other people have had issues with the fuel relay (not just the fuse found under the hood). In my 1999 it's above the gas pedal. There are 4 relays on a little bracket and its the one with 4 wires and light green plastic on it (the forward, outboard relay on the bracket; top right relay if you're on your back looking up at it). Apparently, they're under-powered for the application and as they go bad, corrosion and charring will build up on the mechanical contacts inside the switch. This buildup can cause the switch to either function intermittently (as it does for me sometimes starting and sometimes not) or completely cease functioning. I removed the relay, opened it up, removed the tiny philips screw on the inside (to enable me to move the flapper thingy out of the way) and used a 2mm flathead to scrape the gunk off both of the contacts. I put it all back together and reinstalled it and the fuel pump immediately started running when I turned the key to run.

That said, I don't think just cleaning it like this is a good long-term solution, and if it's a known bad part then I don't see why paying $70 is worth the replacement if it's gonna crap out on me again. I'm thinking about getting this upgrade from flyin miata. Thoughts? I wanna give it a few days to make sure this actually is the cause of my problem, and if it is then I'll invest in the long-term solution.

Although I do find it fairly conspicuous that the fuel relay should fail just as I upgrade injectors. I know that correlation does not mean causation, but still I wonder....

 

L2t

 

That mean learn to tune? lol that's what I've spent 90% of my Christmas break time doing. To be fair most of that is just looking through old posts and mentally bookmarking whatever you've said about whatever problem someone is having.

 

Okay. The issue came back, but I finally fixed it. Turns out, when the megasquirt installation instructions tell you to unplug the Air Flow sensor, it's not optional. It's good now and the fuel pump engages every time I start the car instead of intermittently.

 

Maybe unplugging it was in the instructions for a reason? Good to hear you got it going.

 

maybe.

 

Turned out it was the fuel pump going bad. I had the issue again, got pissed, decided to throw money at the problem till it was fixed, bought a stock replacement pump, installed it, and it's been over a month without the issue. I just wonder why an injector upgrade would cause the pump to fail, or why it would sometimes turn on (and stay on) and other times just ignore my plea for fuel. Oh well. I wish I had been more patient though and gotten an upgraded pump for future reliability (and more power later on) but what I have now should be plenty for my goals.