Crank Trigger/ECU Help
 

I have some problems with a new set up I have been trying and no one local has been able to help much with it. On our drag car, the 1964 GTO, I have been trying to upgrade and use an ECU (Engine Control Unit). I purchased a new MegaSquirt Gold Box from efisource.com. I have a friend that has successfully added it to their car, with a Pontiac engine and it even helped pick the car up some. I have already talked to him and he is at a loss with my problem as well.

Anyway I have installed the Megasquirt (MS3) and I am currently using only a toothed crank trigger wheel as the tach input. I have not yet installed a cam sensor, but will either convert the distributor to use as a cam sensor or get one of those trick Luhn Performance pieces. I am no longer using the distributor to fire the car. I have went with a coil near plug setup using stock GM truck coil packs. The coil packs are the D581 Square coils. I have had the engine fired up and at idle and lower RPM the car sounds great. I revved it in the driveway and it sounded pretty good. I did notice on my laptop that it had a few missed syncs with the crank sensor. Last fall we went to the track to try out the new set up and it ran horrible. Idle and low RPM still sounded great but in the burnout and going down the track it would stutter and sound like it was on a rev limiter.

So I came home and talked with efisource.com and they told me several things to try such as grounds, different crank sensor, plug wires, plugs and nothing helped. At that time I was running a 60-2 crank wheel. I thought that maybe the sensor couldn't keep up with that many teeth, so I bought a 36-1 trigger wheel. The car sounded good and would rip to about 6,000 RPM in the garage without issue. I did have about 5 missed syncs though according to the computer. I thought my problems were fixed but it was too late to go to the track as they had closed for the year. So this past Saturday I went to the track and the car did the same thing. Sounds great at idle and up to around 3,000 RPM then it stutters like on a rev limiter. Seems like it is losing sync again.

So my question for you all is why would I be losing sync this way? Why does it only seem to show under higher loads like burn out and going down the track, as well as when higher RPM zones? Thanks in advance for any help you may give me.

Can you share the MSQ, and a datalog? Have you verified that your timing stays steady when set to fixed, as rpms rise. Are you using shielded wire for the crank sensor? Avoiding high voltage pathways to the ecu? What kind of sensor on the crank?
ETA: a datalog, and a tooth log would help. I'm not great with the trigger logs, but Krisr will see this most likely and he is.
I would highly encourage you to join the MSExtra forum as well. They have people intimately familiar there as the members include designers developers and builders of the hardware software and all.

I will have to get the log and tunes off of my other laptop, and it is out in the garage. I have the Holley 554-124 crank sensor. I have verified that timing stays rock solid on fixed timing. It is a lot more steady than when using a distributor. I have moved the sensor wire and it hasn't changed the problem. Maybe I could wrap in aluminum foil for a test?

That may not tell you much. Were the wires wrapped in a shielded cable when you got the unit? The shielding is particular in that it needs to be grounded only on one end and preferably the ecu end. What type sensor is the Holley? VR, Hall, etc.? You could need a pull up resistor possibly, depending on what it is. It could be the rising/falling edge setting. It could be several setting in the tune actually. Hard to tell without more info.
And see my edit in the other post about the MSExtra forums. https://www.msextra.com/forums/
And ask a moderator to consolidate these two posts or you'll be trying to keep up with 2...

I see it's a hall sensor, that requires no pull up resistor WITH HOLLEY... I know this one works reliably and requires no pull up with MS. https://www.diyautotune.com/product/...sition-sensor/
Not that you wanna buy another after what that Holey cost... Be SURE, you're following the directions about gap, and that concentricity is GOOD. Runout is bad... And ESPECIALLY the clean power and grounding to sensor ground. Battery in the trunk? Mine is. I ran a separate 12 gauge wire to a 4 position Blue Sea fuse panel that only powers the ecu and the crank/cam sensors(and leaves one available for when I add a Microsquirt for 4L80E control later) FWIW

Also verify coil power grounds are grounded to block or head, and the other to sensor ground. "A" is the power ground. The manuals go into great detail about all this. Heed all the warnings, and take it literally.

I don't believe they were shielded. It looks like standard wire insulation to me. Maybe that is it. Would I should just the signal wire, or all 3 wires (Switched 12v, Signal, and sensor ground)? I have tried the rising edge falling edge setting and it didn't change the sync issue. I will try to get the tune on here tomorrow evening and maybe you can take a look. I will definitely look at the other post on MSExtra. Also, should I be getting power for the crank sensor from any switched 12v, or should it come from the VREF wire that comes from the ECU? Right now it is coming from a standard switched 12V.

All the chassis grounds are grounded to the midplate. I talked to Mike at EFI source and he said that should be good. I also ran a ground to test from the battery all the way to my ground stud and it didn't change anything.

http://www.msextra.com/doc/pdf/html/...dware-1.4.html
Link to a page in the manual to see if the Holley sensor has built in pull up, or needs a resistor. Download the whole thing if you haven't already.

I would shield only the signal wire. Shielding grounded to sensor return ground, ecu wire. The end by the crank insulated where it can't make ground. I use 12v on mine for crank and cam. Clean switched 12v. Like I mentioned earlier my ecu, crank and cam power comes from a dedicated fused, switched source.
ETA: Did you make the ground you ran for the test your main ground from the battery? You can create ground loops if you left another ground from the battery Goin somewhere else. My battery(trunk mounted) has a 00 welding cable as a ground to the cylinder head and all Ecu related grounds go there too. It seems nit picky or particular, but I assumed there was a good reason for their directions, and followed as literally as I understood.

I need to clarify, the shielding should be insulated everywhere to prevent grounding anywhere except at the ecu sensor return. Double grounding the shield wire just makes MORE funky stuff...

no experience with this stuff. But...

Crank and cam sensor wiring ought be twisted wire with a ground sheath grounded only at the ECU, not the motor.

Coil Pack grounds have me figuring the Ground path needs to be the Alternator case, not the ecu. ECU grounded to Alt case too. If coil pack have " factory wiring to ECU" then a decent 4,700 uF Cap and 0.1 uF on the ECU 12V may help.

coil pack wiring ought to be twisted if possible.

Check the alternator brushes and slipring for smoothness.

Crank position sensor gap to not vary with vibration.

Beg the company for another ECU to rule-out a faulty box.

Definitely no on grounding the coils to alternator case. Proven reliable method is cylinder heads across installation of these coils on many and varied applications. Sensor grounds absolutely to sensor ground. Twisting the wires is good, especially VR. More important is probably his unshielded signal wire.

Wow, sounds like the polarity (trigger wires) are backwards. Idles but won t rev. JMO.

Hard to do as only one wire sends a signal. I don't think it would work at all if power and ground were reversed, but I guess there's always a possibility.

Also, for the OP, in your logs, when it shows a sync loss, there is also a place which reads "sync loss reason" and a number, which corresponds to a list of reasons in a troubleshooting section of the manual. Would be a good thing to know, along with is it consistently(every time it happens) the same reason.

What are your dwell settings? Certain coils do strange things when the dwell is set too high

He's using 581 coils. I leave my 585's at 3.8 for dwell as word has it auto fire can possibly happen over 4. I'm unfamiliar with these, but maybe they have the same characteristics? Mine will turn 6300 in all gears with no issues...

Hey Scott,
I am having trouble uploading my tune or data logs. Do you have an email or something that I could send them to so you could take a look?

I will send you a PM.