Another Megasquirt conversion: VIN00910

[ramblinmike]

So I've been lurking on here for years and watching you all convert to EFI and never quite getting up the nerve to do it myself. In December I was able to do some side work and, well, that money went into me converting my car from K-Jet to EFI.

The hardware side of the conversion is done: I sourced a Z7U manifold and injector rails and was able to make an adapter plate to mount a throttle body off of a Jeep 4.0. The Jeep throttle body allows me to use the integral TPS and IAC that were not part of the Z7U throttle body that came with the manifold.

Since I had no idea how crazy I was going to get with this thing in the future, I bought a MS3X with the relay board for this conversion.

I have everything installed and plumbed and, as far as I can tell, the wiring completed for the new sensors, injectors, etc. My current goal is to get fuel-only running first before I do anything with running spark control, as you guys have all mentioned that fuel-only is the easiest way to go. Since I'm a complete noob, I took your advice.

I followed the guide opethmike posted and used the settings he suggested in his writeup for the initial settings in TunerStudio. The car started right off but immediately started missing like crazy and running extremely rich. The sync loss counter started counting up quickly before resetting to 0 and starting over while the sync "light" at the bottom of the gauge screen flashes from green to red constantly. The 'Engine RPM' gauge flashes red repeatedly with the displayed rpm quite literally going from 10,000+ rpm to 0. It shows what I guess are 'normal' rpm readings while the starter is cranking. It only goes crazy after the engine starts.

I have the ignition currently set for 'basic trigger', as the car doesn't start at all when this setting is changed to 'fuel only'. I started with connecting the "tach" terminal on the relay board to the white/slate wire in the connector for the old rpm relay. After seeing all of the sync issues, I moved it to the white/slate at the old idle controller connection behind the driver's seat. I have not tried connecting it directly to the - terminal on the coil, but I know I read someone on this forum had issues with that placement. I've read so much today that I don't remember whose thread that was on.

The MS3X and the LC-2 wideband are both grounded together at the same place behind the passenger seat at the bulkhead ground. There is an 8AWG wire connecting the battery to this bulkhead connector and the engine block. The MS3X constant 12+ is wired to the battery directly and the LC-2 is wired as it showed in its instruction manual with a relay connected to the battery +. The trigger wires for both the MS3X and the LC-2 relay are connected to the green wire at the old rpm relay connector.

I've read several threads about sync issues, but mine seem much more severe than what I've read on other's posts. I have things grounded together like others suggested. I've been running an Accel coil for the past 15 years with it wired to receive a full 12V, but I swapped the original coil back in and moved the wires around at the resistor to their original positions without any effect.

I guess I should say that the car was running before I took it apart. As far as I know there wasn't any ignition-related issues. I had done the coil swap long ago on the suggestion of a local club member right after I bought the car.

Where would you guys start? Is there something from tuner studio I should post here? I played around a little with capturing a log file showing the things its doing if that would help.

Thanks in advance!

Mike

[powerline84]

So I run spark trigger direct from negative coil . When I first started my car I was getting the same sink loss symptoms you got. Then Fabombjoy was nice enough to let me know that the megasquirt ecu is not shipped set up for negative coil input. So you have to take your ECU apart and move some jumpers/switches. Let me see if I can find the pics from me doing it based off his help.

[powerline84]

Screenshot_20200405-192659~2.jpg


I believe these are the spots I changed. Get into the hardware manual for ms3 (Google it it's free should pop up) and go the the part about setting up the ECU . I'll see if I can find more info and hopefully Fabombjoy will chime in.

[powerline84]

Ok for my setup (negative coil input ).

You need to have
jp1 on 2-3,
j1 on 1-2.
Xg1-xg2 connected

That is referenced in the pic above.

If you are running negative spark and haven't touched your ECU I guarantee it's wrong and that's your problem. Go negative coil direct. Make the changes to your ECU board. Pat and I have that setup and my car starts almost instantly. No sync loss

[ramblinmike]

Holy smokes. I didn't know there was a different jumper setting for negative coil input.

I'll do that and post back. Thank you.

[powerline84]

Me either it was one of the many mistakes I made In the road to EFI lol

[FABombjoy]

There were definitely issues with using the VR pickup on the distributor. Some MS board revisions were better than others and it sounds like an in-line resistor was needed.

This approach was only taken if you wanted to run full programmed ignition from Megasquirt, removed & locked out the distributor advance mechanisms. TBH I'm not sure that the few minor gains you get from MS ignition control are worth the extra work on a non-turbo car. Idle advance control is probably the largest benefit. You're still only as accurate timing-wise as the VR pickup can be which is 12 events per 720 degrees of crank rotation.

Negative trigger for fuel-only though will work for you once the jumper & settings are correct.

The only downside of coil negative is it can be susceptible to solenoid / relay / coil noise if you're missing filter capacitors (from the cooling fans, AC fan, AC clutch, things like that).
It probably won't cause any issues running but you would see it as a strange once-sample spike in RPM w/ creates a brief rich spike in fueling.

Once your MS box is set up for coil negative, any of the white/slate RPM wires that sprawl throughout the car will work fine as your RPM pick-up point.

[AdmiralSenn]

My experience was the opposite of most - I had terrible noise problems with everything I tried, until I switched to VR input running off the distributor pickup, and tuned it using the on-board adjusting pots. I used shielded wire for the inputs with one pin being attached to the shield and one to the core, and IIRC the shield was attached to the sensor ground on the board and the core to the VR in pin (don't quote me on that it's been several years). This setup ended up with a nearly perfect VR input and I never had ignition trigger issues again. Bonus points that it can be run straight off the existing pickup wire in the relay area so one less wire to run.

[Bitsyncmaster]

My idle ECU can provide a cleaned up ignition signal that a few users have used but most people going MS end up removing the idle ECU.

[ramblinmike]

Well, I need to thank powerline84 because his suggestion worked!

I was able to get the car started tonight without a single sync error in TunerStudio!


https://youtu.be/m_Pp-PnyJBo

I was able to get the car to 'run' immediately after making the jumper changes powerline84 suggested, but it would not idle on its own. After much reading and tinkering with settings I was able to get it to idle fairly smoothly at 1500rpm as in the video. I was pretty happy at that point, so I spent the rest of the evening texting everyone and sharing that video!

I had some of that plastic wire loom wrap here at the house, so I wrapped what I could:
IMG_8719.jpg

I've been doing some reading about getting the idle to lower where it should. I have it set to idle at 700, so I don't know if I have the IAC wired incorrectly. As far as I can tell the idle stop screw on the throttle body lets the butterfly completely close. I have the distributor solenoid wired to ground to fidle on the relay board and I followed the suggestion in opethmike's writeup to have the ecu ground the solenoid when I'm just off idle.

I want to get the rest of the harness wrapped and get something figured out for the air filter before I drive it, but the lack of any sync issues and the engine running made me pretty happy today.

Thanks for the replies!

Edit: the YouTube link didn't work so I just pasted it in the body of the post.