Megasquirt ms3x randomly shuts down

[K-Wired.]

Hello everyone,
I have a strange problem with my ms3x turning off. I rechecked my wiring and everything seems okay, I have tunerstudio plugged in and I noticed it would randomly go off line and my fuel relay would click turning off the fuel pump but main relay still sends the 12v to main fuse. I checked the db37 connector and I do have 12 volts coming in from the fuse, when I plug the db37 connector again I can hear the fuel pump turning on and im connected with megasquirt in tunerstudio. Sometimes it stays connected for 20 minutes, sometimes It goes off line after 10 seconds or 2 minutes. Can it be a bad db37 connector or perhaps something with megasquirt itself? Anyone else had or heard of a similar problem? I made sure everything is tight, but i still get off line in tuner studio. Only thing done to the ms3x was installing the knock module and everything seemed to be working fine, and this problem started a couple days ago. If anyone needs more info let me know, thank you!

[kjones6039]

Do you have a log of it randomly shutting down?

Ken

[K-Wired.]

I believe in this log it turned off on me, ( Log might look crappy at the beginning but towards the end the car started running better because I unplugged the alternator which caused the car to idle like crap and adjusted the fuel pressure ) Car was running and randomly turned off and automatically went off line on Tunerstudio without me touching the key.

Thank you!

[K-Wired.]

Anyone? Maybe someone has an idea what should I be looking for to solve this?

[nathaninwa]

This is my way of tackling issues like this. We need to verify its the car or megasquirt. So in this situation I would find a known constant 12v supply, even if I had to run a test lead into the cabin. Power megasquirt up with this wire and start/drive the car. You could have a bad ignition switch or something random in the car side. This will define exactly where to start looking

[K-Wired.]

Okay Nathan thanks for responding, maybe I will say what I already done. I changed the ignition switch from my other 240sx not only because of this issue but also because the ignition switch I had wouldnt always catch and it became too annoying, Ive connected the red 12v wire that goes to the megasquirt straight with battery through 3 amp fuse not to burn anything up, still it would turn off and once it turned off, I unplugged the ms db37 connector to find I actually do have 12v coming in, as soon as I re plug it I automatically connect to tunerstudio and fuel pump turns on. Right now I think it might be either ground or something with db37 connector or megasquirt itself. I was wondering if maybe someone already had a similar problem but seems like I am the first one so I just gotta find the solution on my own. Thank you!

[K-Wired.]

I got the data log in which I noticed that just before turning off the megasquirt gets 17-18 volts from the battery and then shuts off. Any idea what can be causing such Voltage spikes and then turning off of megasquirt? All grounds have been cleaned plus I've putted a bigger ground between the engine and the chassis. Please look into the data log and towards the end you will notice the voltage rising. Thank you

[nathaninwa]

I wonder if the range of the 5v regulator inside megasquirt shuts down at 18v?

How about this, do two more tests. Wire it to the battery like before and put a voltmeter on that wire and watch it. See if the meter spikes too. Then unhook the alternator and do the test again. Could have a failing voltage regulator.

[K-Wired.]

Nathan, as of right now when I was testing this, the alternator like the whole engine bay harness was unplugged, only thing that was hooked up was the Ground to the engine and then ground between the engine and the chassis, 12v to megasquirt was going straight from the battery though a 3 amp fuse and then straight to megasquirt.. Still had the same problem, then I found somewhere on the forums that someone had a similar problem with voltage spikes and megasquirt basically turning the engine off. Someone on that post mentioned that the db9 connector, specifically pin #9 might be causing the problem. I've cut my db9 pin #9 off and as of right now for an hour and a half I did not have any issues with megasquirt turning off. Looking at a data log it seems to be stable without any spikes, So now I start to believe that this pin somehow was my problem. I run db9 to usb connector since I dont have the db9 port in my computer. If that was my problem Im glad I was basically forced to go over my whole wiring and make sure everything is working as it should.

Thank you!

[K-Wired.]

Been 2 hours and it did not turn off. I believe this issue is solved.

Thank you!