MS3X VVT - no crank and cam signal issue
 

Hi there,

Making progress with our MS3X VVT setup - have all basic sensors working as well as coils and injectors, but facing problem now with seeing no crank and cam sensor signals at all. Searched forums last night but still unclear as to what the correct MS3 hardware setup is for the Miata NB8B (2005 VVT engine) crank and cam sensors ... VR, Hall, or something else. Mazda is running a 12V supply to the crank and cam sensors which suggests that they are the hall-type, but the DIYAutoTune instructions for Miata suggest to use a VR input and that's how our MS3X hardware is configured now (jumpers set and pull ups installed).

The sensors are currently wired with a 12V supply, ground and the signal wires going to the MS3 (mainboard crank input / MS3X cam input).

The crank sensor is configured in TS as Miata 99-05, but we are not seeing any kind of signal in the composite logger.

Any guidance would be highly appreciated.

Thanks much in advance.

did you build it yourself?

Post pictures of your board.

They use hall sensors, but the VR input is like a universal input and can take in hall signals.

What documentation did you use to build it (if you built it yourself)? I used Westfields guide for the crank input with success: 99 ? 05 MS3 | Frank's Westfield MX5 99 ? 05 MS3 |

Go to Part 5, Step 2 in the Westfield guide and make sure your voltages check out.

adjust pots

Composite log and pot adjustment

Thanks for all replies.

Purchased the MS3X second hand from a friend who crashed his car (not a Miata). The crank input was originally configured for a hall sensor - we changed it to VR as this seemed what everyone is using for a Miata (higher noise suppression).
Used the DIYAutoTune v3.0 hardware manual as well as Frank's guide for the input modifications. The pots are all turned counter-clockwise as far as possible. Verified that the crank and cam sensors are getting 12V via fuel pump relay.
Sensors are grounded at our main ground location for everything MS3 at the back of the engine (intake side).

Hope to be able to pull a composite log and take the ecu apart for some pictures of the boards later this evening when home from work.

What's the correct setup for these sensors in TS?

Thanks much for all the help in advance :-)

MS3X board pictures
 

Attached are some pictures of my MS3X boards. Also tried to pull a crank log file from the composite logger, but all log files I recorded are empty (zero bytes), so there seems to be no data at all coming from the ecu, which is weird (they also don't upload as attachment here for some reason).

I will try to set the pots and check for 2.5V at the right places tomorrow.

Thanks much for your assistance in advance.

fwiw, you need a pullup on the adapter board too if you want alternator control to work.

im with everyone else on the adjusting pots now.

I dont even check voltages:
spin R52 & R56 CCW at least 12 times. Spin R56 CW 8.5 turns.
on the adpater board, spin the two back at least 6 times. Spin R11 CW 3.5 turns.

Thanks, Braineack. I will adjust the pots tonite and see if that fixes the problem.

Any recommendation on what the best setting for Ignition Options in TS is? "Miata 99-05" or is it better to chose "Toothed Wheel" and configure it for the 4-1 Mazda trigger wheel?

Cheers

Thanks also for the pointer regarding at the need for a pull up for alternator control. We are running a 94-97 alternator so are not going to use the alternator control feature in the MS3X.

99-05 obviously.

Some progress
 

Progress!!! Thanks for suggesting to adjust the input pots. We are getting signals now. The cam signal looks like it should be, but we are getting only a single bar from crank at the very end of the crank cycle. Please see attached composite logs.

Tried various different settings in TS (Ignition Options), but no change. Also adjusted the sensor / tooth wheel gap, but no difference either. Also played around with the R56 setting, again same result.

Any ideas, why the crank signals are not coming in as they should?

Thanks much in advance.
C.

Composite logger screen shot
 

Forgot to include the screen shot from the composite logger ...

Anyone willing to share a good base map for the VVT engine to get us started and the engine running?

Stock?

Sharing maps is like sharing condoms. Too many configurations: ribbed for her pleasure, fruity, studded, extra thin. Not everyone uses a magnum.

did you add a pull-up to the VR input circuit?

Yes, pull-up is installed with a 1k Ohm resistor - please see attached picture.

Could it be a defective crank sensor (how do you test it?) or a wrong setting in TS?

Thx.

What's the gap to the crank sensor? I spaced mine with a Safeway club card. CVS might work too.

I used my VISA Black Card

Adjusted the gap visually as best as possible yesterday, but will adjust it again today using the suggested plastic card and report back. Regarding the pull-up ... I used a 1k resistor - some people say the resistor should be 470k. Does this make a big difference in your experience?

Is there a good way to test the crank sensor? It's the one that came with our junk yard engine, so we have no way of knowing if it actually works.

Thanks.

Well, I'm about to pull my hair out ... still no crank signal ... kinda exhausted all options. Double checked wiring and every wire connection tested ok. Ordered a new crank sensor since this is kind of the last possible cause other than a problem with the ecu itself. Will test with new sensor when it arrives on Monday.

Does anybody know someone in the San Francisco Bay Area who has the ability to test / check the MS3 VR input circuit?

Thanks for any tips in advance.

Strange. My 01' Miata worked fine without a pull-up, on two different main boards. I recently upgraded to a MSpnpPro so I am not going to waste my time messing with my old ECU, but I wonder why I was able to get it to work without it, if it is in fact necessary.

Also, what is connecting your megasquirt to the sensor? Are you using some sort of adapter harness or box, or are you spliced directly into the car wiring. I can't recall if I saw what the overall application is.

EDIT: From :https://www.diyautotune.com/support/...rt-your-miata/If that was done, I don't know what to tell you. I guess I was lucky all those years.

How did you adjust the pots? If you just counted turns, I would try using a multimeter and measuring voltage as described in the manual. I had the same issue with mine after I counted turns and lost track of how far CCW it had gone. I had the same single spike of the crank signal at the end of every plot, even though it was getting no signal. Adjusted to 2.5V and the car started.

no it didnt.

Ok, let's be clear of what we are both saying here.

I am saying that my car fired and ran without pull-ups (at least on the crank sensor, because the cam sensor pull up may be installed on my MS3x board).

Wither or not it ran optimally is another story, but I am 100% certain that there was no pull up on the board I looked at on my bench yesterday, and when I get my fully built ECU back I will happily pull it apart and check to see if there are any hidden pull-ups I may have missed.

This may be the reason why I had so many problems adjusting my VR pots.

So, should you install pull-ups? Absolutely. Somehow I must have been the anomaly. My only point in replying is to figure out if you are saying that my car did not run without pull-ups, because clearly enough for me, it did.

We did not measure voltage, but went through the whole pot range in cycles with two pot turns at a time - didn't make any difference.

Re-checking the wiring again, discovered an error though. Due to using difference wire colors for wire extensions, the black wire (ground - mainboard pin 1) in the shielded crank sensor cable (DIYAutoTunen pigtail) got accidentally connected to the signal wire (blue) of the crank sensor. Not sure if this exposed the VR input to 12V and could have damaged anything inside the ecu? Changed the wiring but still no signal.

Can someone please verify the following crank sensor wiring that we currently have:

- Black ground wire in shielded crank sensor cable (ecu mainboard pin 1) to ground wire on sensor
- White signal wire in shielded crank sensor cable (ecu mainboardpin 24) to signal wire on sensor
- Separate fused 12V feed to 12V wire on sensor

What about the grey wire (ecu mainboard pin 26 - also part of the TPS wiring) which is referenced in the DIYAutoTune wiring diagram as needed for a hall type sensor?

Thanks much in advance.

Are you getting my private messages Coma? I sent you some files to check against.

Thanks for sharing your info, Chiburbian! Will review later today and will email you in case of any questions.

It's impossible to get a signal without one. Check R13 to R45; that's where I put mine.

Quick update ... just adjusted R56 to get the voltage at R54 dialed in at exactly 2.5V, still same problem and not getting any signal but just one blue crank bar at end of crank cycle. The new sensor arrives on Monday, but this kinda already looks like it might be a problem with the ecu.

Does anyone have advice in regards to troubleshooting the VR input circuit?

If we get one blue bar in the composite logger and the VR input range (R56) adjusted to 2.5V just fine, is it an indicator that the circuit is working or could there be other components damaged (IC, etc.) that cause the "no signal" problem?

Thanks much in advance.

This is a situation where a jimstim would have been really handy... :)

the one blue bar at the end of the cycle isn't your crank sensor sending a signal, it's just a random blip in the log when you stop cranking.

We have crank!
 

Problem solved! Had an Electrical Engineer friend come over with his oscilloscope yesterday to help us solve the mystery of the missing crank signal. It took him about an hour to hunt down the problem. Turned out to be a broken trace in the VR circuit on the mainboard - unbelievable!

So we are seeing the crank signal now, yay (see attached screen shot), but noticed that the rpm reading in TS is not consistent during cranking of engine ... you see rpm for a couple of seconds, then briefly goes to zero, then rpm again for a while, goes to zero, and so on. Is this normal or is this an indication that something is not syncing up correctly, yet?

Wanted to relay a big thank you again to everyone who has helped us with guidance and insights so far!

Cheers
C.

the polarity of your crank and cam inputs aren't matching.

what did you do to flip the cam input like it is? your earlier log it looked correct, where it's failing edge--now it's rising.


The double cam marks should be happening between the crank marks.

Ahh, thanks. That might have gotten changed in the TS Ignition Options settings by accident while we tried to troubleshoot the crank signal problem. Will check and change it back to falling edge again later today and then see if everything lines up.

Thanks a lot.

We love that sound ... :-)
 

Hi there,

Once again a big THANK YOU to everyone who helped us getting over the initial hurdles - much appreciated!

Yesterday evening was the big moment of truth as we tried to start the engine for the first time running off the MS3X ... instant success !!! Engine ran almost too smooth for the first attempt ...;-). Now off to the dyno to get this baby tuned for max performance.

This is a great forum.
Cheers
Conny

really help full
 

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