Hi guys,

it was already late last year, that I encountered this problem - the car was outside for a night at ~0°C (32°F) and the car didn't want to start.

The car was of the road for 3 months - last week I took my MS from the warm bench and put it in the car. Near perfect start.
Today I tried to start the car after the MS was in there for some days at ~-3°C.
No f***ing start. I did an composite log - no crank signal.
Took the MS out of the car - put it on the bench (Jimstim) no crank signal too...

Screenshot Composite log - on the bench powered by Jimstim:


What part in the MS could cause such behavior?
My MS is made after Franks instructions here: 99-05 MS3 | Frank's Westfield MX5 99-05 MS3 | & Megasquirt site

EDIT: The MS just warmed up at my office for some minutes - now I get random RPM reading (cutting out heavily)

 

maybe need to reposition sensor?


oh n/m i didnt read fully. you're using the VR input? I'd check the voltage reading at R32.

 

Where and what should I be measuring there?

According to Frank it's R11 that has to be set...

 

that's what I meant. R54. make sure it's at ~2.5v-3.0v

 

R11 was set to 3.25V - reset it to 2.75V
R56 was set to 3.75V - reset it to 2.75V
we'll see if that helps. ;-)

 

Just one more question - (I am going to freeze the MS tomorrow outside and then test on the bench) - how would the temperature and the loss of the signal correlate (together with the slightly wrong set poti's)? Maybe one of the electrical experts could chime in and school me there...!?

 

That's the weird part- normally the performance of most electronic components improves as their temperature decreases. There are exceptions of course (batteries, for instance) but when it comes to nearly everything else including semiconductors, they perform best when they are at what humans would consider to be uncomfortably low temperatures.

 

crank signal is R56. 3.75V was probably just a tad to high to distinguish between hi (5V) and low level (0V). I always set them at 2.6V, never had a sync problem. You probably adjusted in house (nice and warm) where it was just on the edge of working and now that it got colder, you got outside the tolerance.

 

-little update:

Had the MS in the cold for some hours at ~-3 to -4°C (~25°F) - took it to the bench - perfect RPM reading/signal pattern



Put the MS in the car again, I will leave it there for some hours in the cold again and try to start this afternoon. (I'll take a log of course...)

Greets

 

looks like a good clean signal.

 

Final update - starts like a champ...

SOLVED!

 

WOOT. Awesome information hear. love to hear success stories.

 

I'm bringing this one back up as it's most relevant to my problem. Trying to get a 00' up and running on the new MS3x with V3.57 main board. Starts and idles but won't rev past 3k and tach cuts out when it stumbles. Points to a crank / cam signal issue, I got the MS3x second hand and did not touch R11 or R56, so I opened it up on the bench to see what the voltages are set to........with the screws fully CW

R11 can only get to 2.37V
R56 can only get to 1.67V

Voltages will go down to 0 if I turn the screws fully CCW. I've verified 5V on VCC. Tried the test on the bench and in the car to verify it's not a power supply issue. I've double checked my jumpers and resistors and they are as this guide shows: https://www.diyautotune.com/support/...rt-your-miata/

Stumped here........

 

Just found that if I fully seat R52 and R32 CCW (hyst adj.) I can get 2.4 volts on both boards now so that explains the difference but not the low voltages. Going to try running the car on it now.

Edit: Runs way worse, will barely idle, sync error counts just count up like crazy.

 

One last update.....I hope. Got the car to rev up and clean itself out, it was pretty flooded once I got the revs up the sync errors stopped and it revs to the moon just fine. This still doesn't explain the low voltages but at this point I buttoned it up and moved on. Very odd issue.

 

You are posting in a thread that has "SOLVED" in the title, most people are not going to come into it unless they are looking for a solution to a problem they are having as well.

You will have better luck creating a new thread of your own instead of hijacking a thread that was lasted posted in four years ago.

 

Ehh you have a point, it's a habit left over from another take no **** site I frequent. If there is an existing thread with the same issue you're dealing with then you bring it back up so that information is all in one place for future members to find easily, really cuts down on the noise.

Issue is resolved so hopefully my ranting into the dark of the net is found by future searches and can help them.