baggedgoods

Well good news. I got to thinking about how I lost my trigger signal beings I had only changed 2 things, injector impedance and wire routing. So I got to digging about hi vs low impedance and the effects of noise. Well I began to realize that I had my CAS signal (pin 24) pulled down with a 1k ohm resistor from the 12v+ of the HIGH IMPEDANCE INJECTORS. I had removed the PWM ?filtering? for the low impedance to high impedance injectors. So I moved the resistor to the CAS 12v+ and voila, perfect trigger edge, and some slight deviation of around 2ms of the teeth in the tooth log The impedance or pwm control must have been a big factor as to why it worked previously that way. Anyway, thought I'd update this post with a success!

I am having rpm loss and crank signal errors while cranking, and while running below roughly 1400 rpm. The car will start with some throttling and run great around or above 1400 rpms. Once I let off the throttle, the car will buck and die. While composite and teeth logging during cranking, I'm not seeing anything close to a proper tooth count, and the rising/falling edges look blocky. I'll attach both composite and teeth logs below as Excel and Megalog files as well as my TunerStudios file. I've confirmed the jumpers J1 and JP1 are correct for the Nissan CAS optical sensor. There is a 1k pullup resistor wired from the injector 12v to the white(pin24 i believe) crank sensor signal. I've readjusted the R52 and R56 pots according to the manual. I read 2.39v at the top of R54 and can't seem to get it any higher while turning R56 clockwise. I have had the car running well previously and I decided to upgrade the fuel system and reroute some wiring to clean it up a bit and am now having these issues. My hardware and settings are as follows: MS2 V3.57 board with a BIP373 transistor 3.4.2 firmware Nissan CAS optical sensor with the DIY 12-1 toothed wheel Single nissan ignition coil -Falling Edge -Going high -Single coil -JS10 (jumped to igbtin within board) Wiring is per MS2 v3.57 schematics. CAS power is fed from an unused relay terminal. No Idle valve 1050x hi z injectors walbro 255lph fuel pump BCPR6E-11 resistor spark plugs and NGK wires I've confirmed the MS has 12v+ and both power and ground leads are good with <0.2 ohms respectively. I've tried moving the MS grounds around the engine bay, from the heads to the intake manifold to the firewall. I get the same measured resistance across each ground position. There was no change in the messy signal. I then tried isolating the noise by: disconnecting the coil. No change. separated the shielded wire from the injector wires. No change (Note: the only un-shielded portion of wire for the crank sensor is where I connected the wires to the stock CAS and for the pull up resistor from the +12v injector wire). Unable to find any noise reduction from obvious *loud* wires, I then readjusted the hysteresis and trigger voltage pots R52 and R56. No change Then within tunerstudios, I introduced 25% noise filtering at .1ms and I can see what seems to be some semblance of square waves. The tooth log still looks as ugly as it did with or without filtering. I'm considering changing out the CAS with a fresh one as I have no way of testing whether its malfunctioning or not. I would prefer not having any noise filtration if that's even possible. I don't like the idea of putting a bandaid over bad wiring. Thank you! Z31 1.msq cranking tooth logger.mlg cranking tooth logger.csv cranking composite logger.csv cranking composite logger.mlg

Thanks sheen. That's what I had thought. I've seen some really weird shit with automotive electrical stuff so I wanted to keep any possibilities open.

Yeah, you're right. I'm talking about the physical wire from the negative side of the coil to the megasquirt. I'll have to test my injectors. So if megasquirt is firing my injectors, it should be controlling, or at least trying to control the spark. And if I do not have a spark but my injectors are firing, then the problem lies elsewhere than from the cas.

I haven't manually checked the injectors themselves but I smell gas so I know there must be fuel coming out of them. The junkyards around here are bogus and not worth it. (Not an open yard and takes them a month to get something miniscule) I have a new one on the way that will be here Thursday. This no spark issue has been bugging me for awhile. The last thing I'm suspecting is a faulty ground wire to the coil. Pin36 out of the Megasquirt. I haven't been able to do a continuity test on it yet, but will do so. I've already replaced the bip373 power transistor inside the board, ignition coil, wires, plugs. The cap and rotor look fine. So I'm down to a faulty CAS, a faulty ground wire, or something else inside the board. Also, I've heard the z31 cas tends to go bad after a couple years so putting a fresh one in isn't a bad idea either.

Hey guys, would a faulty cas still read cranking rpms but cause no spark? I've put a megasquirt in my car and am seeing cranking rpms but am having no spark and am trying to narrow everything down as best I can. If so, is there any plug and play alternatives for the 1985 300zx turbo crank angle sensors that would be more readily available that I can just drop in.(I don't really want to wait up to two weeks for a $200 crank angle sensor) Edit: had the car running and driving for a few days when it suddenly died and now it has no spark.

I just installed what DiY gave me. Metal screw with plastic insulator. Alot of people tend to over look things so I have to say the same shit twice so they get all the details. But no, the only change I made to the board was the transistor installation. And no, there was nothing installed into q16 prior to me installing the bip373. Only js10 was to the center hole. I found a diagram for mounting the transistor and followed it to the letter which seemed to work for however long I had the car going.

I'll double check on it. You'd think if it was electrically conductive, it would have grounded out long before it did. Who knows.

It is heat sink grease. It's used mainly in putting processors into the motherboard's of PCs but I'm pretty positive it is non-conductive. Tried turning it over and it won't start. I believe I fouled out my plugs from trying to start it so much without spark. Gonna pick up a new set tomorrow and go from there. Crossing my damn fingers once again lol. Welcome to the race car world I guess

Took the old transistor out and found that the screw holding it on grounded to the wall of the transistor mounting hole. I had the plastic insulator installed but it seemed to arc just below the bottom of it. So, dropped a new transistor in and I'm about to test it out. Will update soon. Wish me luck.

Well I just dropped a new oem coil in but haven't manually discharged it because you'd think it would work just fine. And I tried starting it but still no spark. That's why I'm being lead back to the transistor. I'll let you know how everything goes when I put the new transistor in.

I haven't found any test procedures for the transistor so I'm just going to replace it and see where it gets me. I'd very much like to know what or how it failed. But sometimes if it works it works. What really puzzled me was, after the car died, I was checking my wires and the power wire to the coil wasn't getting power to the coil. Fuse was fine. So immediately I replaced that wire and confirmed 12v at the coil. Still no spark. I'm not sure if that had something to do with the transistor failing or just the wire had gone bad (even though it was a brand new wire.)

Off the top of my head, the primary coil is about 1 ohm and the secondary around 10k ohms. So it is a low resistance coil and I ran 3.1ms of dwell through it. That doesn't seem like too much dwell time to me. I don't even touch 6k rpms so I don't believe it would harm anything being that long at higher rpms.

It looks fine to me. I used the mica insulator as well as thermal compound. And yes, that was one part of the problem. I replaced the coil but have not tested it manually because it's a Brand new coil. Also, for some weird reason, my power wire to my coil wasn't getting power to the coil anymore so I replaced that as well and have confirmed 12v at the coil. So this leads me back to the coil not getting grounded by the megasquirt which is through the bip373. And I made sure my js10 to igbtin was connected and looked physically okay and tested okay.

It does and it's installed. I noticed a few hardware pieces on the heat sync that had the mica insulator as well as heat sync grease/thermal compound so I put some on as well. But that would make sense, thanks for clearing that up. Also, I bought the board preassembled so that would explain my lack of knowledge towards the board side of things.