No RPM - MS3/MS3X 1.6
 

Now, I am having some problems getting a CRANK signal it seems.

The car is a 1992 1.6 Eunos Roadster with a stock engine and wiring.

The Megasquirt is the MS3/MS3X according to Frank/Brain's 90-97 guide.

I am reading 2.6-2.7v between R17 and R54 and ground (car chassis) after some tweaking of the R11 and R56 pots so I think the VR input circuits are set up correctly.

The stock AFM is still connected as I have not yet re-wired the fuel pump.

Right now the coils and injectors are unplugged and I'm cranking the engine in the hope of getting a sync following this guide. However, there is no RPM signal at all and the Composite Logger records a Cam signal but no Crank signal:
https://www.miataturbo.net/attachmen...ine=1388214297

The link on Frank's guide for the startup MSQ is dead so Brain kindly gave me one of his. I am not running a turbo (yet) so I have turned off boost and have tried tweaking a few of the settings advised in other posts.

I have attached the MSQ and logs.

I would REALLY appreciate some help with this. Thanks in advance!

The image is a little low-res so here is another.

https://www.miataturbo.net/attachmen...ine=1388214838

you're not getting a crank signal. did you tune your pots correctly? jump the mainboard correctly for VR in? build the harness correctly?

I tuned the pots so I was reading 2.6-2.7v on the top leg of R54 and the bottom connector of R17.
I did notice that on the bench the voltage on R17 would max out at about 2.35v however. In the car and with the laptop plugged in I was able to adjust it to 2.6 though - but this would only affect the CAM input right? Which seems to be OK.

I've checked the wiring and confirmed that:
There is a (white) wire between 2E on the connector and pin 24 on the MS3 mainboard.
There are jumper wires between: JS9 and S12C; TSEL and VROUT; TACHSELECT and VRIN
Jumpers are installed on the MS3X card in JP7 and JP3 only (no jumper in JP8)

Are there any other tests I can perform to further try to isolate the problem?

Thanks for your help.

So, I reheated/resoldered every component on the main board as well as all of the wires on the harnesses and cleaned off all of the flux. Trying the dry crank again, this was the result:
https://www.miataturbo.net/attachmen...ine=1388648880
TS read 280-288RPM

I guess there was a cold solder or short that was screwing things up.

Hoping to get the car started and running on the MS3 tomorrow afternoon.

Oh and Happy New Year!

Forgive me for bumping such an old thread but I think it's worth mentioning that the OP was onto something here. I had the exact same problem (no crank signal, but everything else worked) for literally years and all I did was touch up a few random areas with some solder and voila. I have no idea what the culprit was, but I guess that doesn't matter now.

very helpful. thanks for posting!