Yet Another Missing Tach Signal

[HawaiiB2200]

Gentlemen,
This is my first post to the forum though I have read extensively for some time. I need your help with the following issue.

What I Have
1) MSII Processor w/V2.9200 code
2) V3.0 Board
3) V2.1 Stim
4) Running TunerStudio


I have arrived at the RPM signal testing portion of the MegaManual with success for all other tests. I could not get an RPM signal initially, so I tested all other inputs. IAT, CLT, TPS, and O2 all function correctly on TunerStudio.

How Its Wired: I have wired this for a pickup right from the coil, though I have left the Zener diode off of "D2" for the purpose of testing as per the MegaManual.I have soldered a jumper in place for the purposes of troubleshooting and will replace with Zener diode once I am successful with Stim testing. I have jumped TSEL to OPTOOUT, TACHSELECT to OPTOPIN, and XG1 to XG2. I have also made the jumper connections for an IAC motor (JS0->IAC1A; JS1->IAC2A, JS2->IAC1B, JS3->IAC2B). I followed step 50B (installed C30, C12, R12, R13, and D1) not 50A, I also installed the VR circuit in case I want to change the setup later. I have not installed the jumpers for the VR circuit.

Troubleshooting Already Executed:
1) Scrubbed back of board with acetone and toothbrush.
2) Check and ensured all components are installed and in the correct orientation.
3) Made sure I was using a fresh battery. I hooked up two regular alkaline 9v and a Lithium 9V. No change except minor bump in voltage for Lithium 9v.
4) Checked voltage at U3 pin #1. Volts read 1.2. U3 is installed with dot in upper left corner facing the heat sink.
5) Jumped TSEL to TACHSELECT and was able to see brief spike in RPM, then nothing.
6) Check voltage on U5. 7.56V on pin closest to DB9 (Stim battery reading 8.1V at same time) 5.01V on pin farthest from DB9.


I will be redoing all soldering until I get an answer to ensure it is not a cold solder joint and will post as soon as I have resolved the issue IF the solder checking does fix it.

In the meantime, help! I'm stuck on this. Any advice, good vibes, or voodoo magic that fixes MS is appreciated.

[Matt Cramer]

Let's test the opto input circuit. With the Megasquirt powered up, apply 12 volts to pin 24 or TachSelect, and check the voltage on the TSEL jumper with a voltmeter. You should read zero volts. Next, ground pin 24 so it has no volts on the input circuit, and check TSEL's voltage again. You should see 5 volts there. Let me know what you find.

[HawaiiB2200]

Apologies for the late reply, I've been out on a field problem for the past week. I came in for a few hours to refit and I got away to run your tests.

I applied the 12V from a battery to TachSelect while the stim was powering the board. TSEL had 91mV. I then grounded pin 24 on the DB37 input and tested the volts at TSEL. 93mV. Didn't get the 5V.

[Matt Cramer]

Check to be sure R13 is 4700 ohms and there is no stray flux or solder blobs on the optoisolator.

[HawaiiB2200]

So I completely replaced the optoisolator with a six pin socket and new optoisolator. Still missing the tach signal. Checked the back of the board, no stray blobs of solder, no messy flux. I've already scrubbed the back of the board with a toothbrush and acetone, twice.

[Matt Cramer]

Any changes to the voltage test?

[HawaiiB2200]

It has been a minute since anything has changed with my board, but I have some updates. I re-installed the MS code onto the daughtercard and now I have some very strange things going on. The tach signal jumps from 0 to 8000 and now all of my other inputs are non-responsive. The fuel pump LED also blinks on and off. TunerStudio is reading the ECU as a MSII with v2.920 code, the software detects the ECU and determines the right code correctly everytime I plug it in. Does anyone have any ideas?

[Matt Cramer]

You need to set the ECU type to MS2 under the general settings.

[ironwill11]

Hey Hawaii2200,

Did setting the ECU type to MS2 under general settings, fix your tach bouncing from 0-8000? I just got done building the tach circuit, and my tach goes from 0-8000 back to 0.

Will