JimStim Tach OK, No RPM in TS (JS 2.0.3, MS2 v3 rev 2.88000)

[Slowpoke_70]

Hello All,

Hardware:
JimStim v1.5 board with 2.0.3 chip
MS2 v3.0 running rev 2.888000
13.5VDC 400mp power supply

Software:
TunerStudio Lite 2.0.8



I bought a used MS2 board that was built from a DIYAutoTune kit. I had the same person that built the MS2 build me a JimStim 1.5v 2.0.3. Initially I thought I had no power to the JS but after some diagnosing I figured out that all the LED's had been installed backwards. After re-installing the main 4 LED's and the top two IGN LED's on the jimstim those LED's passed the assembly tests. I then setup the stim in hall/opto mode with all dip switches off and no pull-up jumper.

The MS2 v3.0, according to the previous owner/builder, was set-up for EDIS with the MS2 running B&G 2.888 code. I have looked at the board and it seems to match the Megamanual instructions for the Hall/Opto circuit perfectly.

So I hooked up the JimStim to the MS2 and connected to my PC. Everything seemed okay on TunerStudio Lite v2.0.8 EXCEPT I didn't get an RPM signal on the TS dashboard. So I removed the JimStim and checked the tach signal using one of the IAC LED's as described in the JS assembly guide, it passed the test.

Then while reading through a lot of forum posts on msextra and jbperf, I found instructions on how to test the JimStim tach circuit while having it hooked up to the MS2. Simply jumper the "TACH" pin to one of the "IGN" LED pins. I tried this without the MS2 connected to my PC, and the IGN LED lit-up solid as soon as I switch on the power. The D15 LED on the MS2 also lit up at this point.

With the jumper in place and both RPM pots turned fully CCW, I began to slowly turn the RPM Fine pot CW. After about an 1/8 of travel, the IGN LED began to pulse and frequency increased as I turned the pot further CW. The FP, INJ1 and INJ2 LED's also lit up under these conditions and behaved as expected. D14 and D16 on the MS2 also lit up and behaved as expected.

So I connected the JS/MS2 to the PC and pulled up TunerStudio. Powered the assembly up and checked for RPM on the TS dashboard. With the jumper still in place, the dashboard shows and RPM signal. BUT, with the RPM Coarse Pot turned fully CCW, I can only get up to 1021rpm using the RPM Fine Pot. If I then turn the RPM Coarse Pot a bit, I can get the gauge to peg, but then returning the RPM Fine to fully CCW won't bring the needle back to zero. I tried several suggested adjustments for the R52 and R56 trim pots, and I get the same behavior.

I guess the really odd thing is that the RPM signal is only displayed on the TS gauge when I have the jumper in place from TACH to IGN LED1. Shouldn't the RPM signal be displayed on TS even without the jumper to the LED?

Any help on additional diagnostic steps would be appreciated. My goal is to verify that the MS2 board/cpu is working correctly before modifying it for my own ignition application.

I have a cheap Digital Multi-meter, no oscilloscope, and I can build an LED "noid light" if needed.

Thank you,
Enrique a.k.a Slowpoke70

[Matt Cramer]

Can you post a copy of your MSQ? I'd like to check your settings.

[Slowpoke_70]

Sure, I will do that when I get to my home PC later on today.

Thank you.