Odd MS3X + JimStim 2.04 Power Issue.

[mega1uz]

Hi guys,

I've managed to assemble a working MS3 with expansion board after a few gotchas (such as not connecting the daughterboard 40-pin connectors properly for fear of breaking something), and have successfully loaded the firmware via USB cable. I also purchased a JimStim v1.5 with firmware v2.04 pre-assembled, and was able to connect it up and test the TPS/O2/Coolant inputs successfully.

The issue I'm having is (I think) related to the toothed wheel setup and RPM signal from the JimStim. I configured a basic trigger setup fine and the RPM signal could be read, however when I configured it for a toothed wheel setup with sequential injection and coil on plugs, it won't read an RPM signal unless I power the unit on/off from the wall transformer—Using the power switch on the JimStim stops the RPM signal working (80% of the time). The wall power supply is from DIYAutotune.

Has anyone come across this problem before? You can view a video on what's going on here: https://vimeo.com/180712932. I've triple checked the MegaSquirt components/connections and all seems fine. I have also adjusted the pots.

Cheers,
Josh

[racingmini_mtl]

What happens if you turn off the JimStim then unplug the wall power supply, replug it and turn on the JimStim? Does that allow you to see an RPM reading or do you still see the same thing? You might also try to keep the power off for longer than that.

I'm just trying to see if there is something in your setup that keeps some partial power at a lower voltage when only switching off which could put the CPU in an undefined state.

Jean

[mega1uz]

Hi Jean,

Same issue applies when following the steps you posted. I left it overnight unplugged with the JimStim turned off, then turned wall power on, and then the JimStim on and no RPM signal.
On rare occasions it will work correctly with that procedure, but the only way to guarantee an RPM signal is to leave the JimStim in the "on" position and turn power on from the wall.

What could be causing partial power to the CPU, and how could I check this? Thanks for your help!

[racingmini_mtl]

The only thing I can think of is that there is something wrong with the switch. If you could try to bypass it by shorting the 2 pins under the board while the switch remains off that might give a clue. Make sure to not short anything else while trying this though.

Jean

[mega1uz]

Thanks Jean - solved the issue. I accidentally left the tx/rx jumpers in place which was causing the issue - always the simple things!!