Megasquirt MS3x 4.0 Startup Issues

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Cdyt7717
Posts: 2
Joined: August 28th, 2019, 6:48 am
Vehicle Year: 1989
Vehicle Make: Jeep
Vehicle Model: Comanche

Megasquirt MS3x 4.0 Startup Issues

Post by Cdyt7717 »

Hey guys, I'm stumped and looking for some assistance with my MS3x initial startup on my renix 4.0, 2000+ cam sensor, LS D585 coil near plug setup. I'm hoping someone wouldn't mind giving me some ideas that could point me in the right direction. I've worked through the quick start manual in order, and I'm stuck at the startup section. I have verified spark/fuel outputs are in sequence, verified base ignition timing, tried to fire it up and got nothing but cranking, it didn't even try to fire. I then removed the injector fuse, switched to wasted COP and tried cranking using starting fluid to verify my ignition system was setup correctly. In this setup, it will crank and fire, but if you try to keep it running on starting fluid it will backfire into the intake. I switched back to sequential COP with the same results. Verified my wiring again, base ignition timing (with timing light), and double checked my firing order using the ignition test mode to fire the coils in sequence. I am stumped to what could be causing this backfire after checking everything. Also, I cannot get it to even try to fire using the fuel injectors, no matter how much fuel I give it. This is my first go around with tuning and I may be missing something silly. I can post pictures of any useful datalog info if needed. Composite tooth logger looks great with no sync loss at all during cranking.
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Cdyt7717
Posts: 2
Joined: August 28th, 2019, 6:48 am
Vehicle Year: 1989
Vehicle Make: Jeep
Vehicle Model: Comanche

Re: Megasquirt MS3x 4.0 Startup Issues

Post by Cdyt7717 »

So I set the plugs on the valve cover and video'd the ignition events during cranking and found out what is going on, just not sure why. It will fire in the correct sequence, then all of a sudden, sporadically fire a few random coils. it seems to only do this after it completes a round of proper sequenced sparks (1,5,3,6,2,4...then 1,4,5). I'm gonna take a look at dwell settings but I don't think that is the culprit.
mpgMike
Posts: 5
Joined: October 14th, 2022, 3:34 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: XJ

Re: Megasquirt MS3x 4.0 Startup Issues

Post by mpgMike »

Not familiar with the Renix stuff, but the 91+ crank trigger system pulses at 65, 45, 25, and 5 degrees BTDC for each cylinder. There is no added or missing tooth to denote cylinder 1. On the scope though, I see that the Cam sensor goes high shortly before the 65 degree pulse for #1.

I am suspecting a dirty signal from the Cam sensor, confusing the MS as to when #1 should fire (and subsequently the rest of the cylinders). In the first scope shot, the Cam sensor signal is in red and the negative blip in yellow is cylinder #1 firing.
cam_cyl1.png
This shot shows cylinders 1, 5, and 3 when the cam sensor is high (centered).
crank_cam1.png
A higher resolution shot of the crank (red) and cam (yellow) sensor relationship.
crank-_cam2.png
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