No Tach Sync for 7-pin HEI

[71gto]

Hello, I'am a new user but have enjoyed your site for awhile. I'm using a Megasquirt 2 V3 board bought from diyautotune and home built, along with a relay board. The distributor I'm running is a Pontiac HEI (counterclockwise rotation) with the 4-pin module swapped for a 7 pin module with the reluctor leads switched for the 7-pin. I'm only trying to control spark. I have good vacuum showing in tunerstudio. The problem: No tach signal showing on tunerstudio and no led's flashing or burning on megasquirt.
I only have pins "E" and "R" hooked up to the relay board so I keep the car running while troubleshooting. "E" is hooked to "B5" and "R" is hooked to "Tach" on the relay board. I've hooked a scope up to the ref. signal from the module and I have a very clean 5v square wave coming in. I have also ohmed out from the terminal strip on the relay board and to pins 36 and 24 on the megasquirt board itself, no problems.
Now for the mods I've done to the board. I originally started with diyautotunes HEI kit. Removing the TachSelect to OptoIn jumper, and the XG1-XG2 jumper, and running a jumper from OptoIn to 5v proto area with inline 1K ohm resistor and another jumper from Tachselect to XG1. Also setting the input capture to falling edge. No luck with that mod, so I went a step further. I tried the transistor mod by soldering 2N2222 transistor into the proto area. Then running a jumper from OptoIn to the 5V proto pin. Running a jumper from XG1 to the collector pin, and jumper from Tach Select to the base pin with a 1k resistor inline. The emitter pin is going to ground. I inverted the input capture in tunerstudio to rising edge. Still nothing.
Of course D1 and D2 have jumpers in them and C12 and C30 are not installed. I have ohmed out the circuit from the DB-37 pin to U3 and all the jumpers with no problems found. I have also tested U3 the only way i knew how buy checking for 5v at #2 pin on U3 while gounding out pin 24 and I can switch the 5v on and off by grounding pin 24 on and off. That was preformed on the diyautotune HEI mod kit installed before I switched to the transistor mod.
That is the sum of things. Unfortunetly I do not have a stim board to test out of the car but with the clean square wave coming in and the complete circuit to U3, I'm guess the results would be the same. Where do I go from here? Sorry, there's no data log to atached because it literally shows nothing but vacuum.

Please help, no more hair to pull out. Thanks

[Matt Cramer]

Can you post a copy of your MSQ and a trigger log of an attempted start? This will let us see what the ECU is expecting and what it's really getting.

[71gto]

I've uploaded the msg. but when I ran the trigger log, I just got the message "empty read:no data received from controller". I also went and bought a new ignition module. It has a nice clean square wave on the scope but the voltage is only 1.5v compared to my old module at 5v. Unfortunately I damaged my old one farting around with it. I'm guessing that should be a problem though, with using the transistor as a means of switching ground for the opto-isolator. That's all I got for now.

[Matt Cramer]

As you do not have a Stim, what happens if you check the output at TachSelect with an oscilloscope?

[71gto]

I checked the TachSelect on the board and I do have my 1.5v square wave. I also checked the transistor and I have my 1.5v square wave on the base pin and I also have a 5v square wave at the same freq. as my input present at the collector pin/XG1.

[Matt Cramer]

The wave should be 5 volts, not 1.5. Is R13 present and in spec?

[71gto]

The 1.5v signal is right off the module before it gets to R13. I do realize that's low, but I'm guess because it's a BWD brand instead of OEM. With the mod I have with the constant 5 volts coming into the opto-isolator and the transistor switching the ground, it's enough to bias the transistor. With reading a good 5v square wave on XG1 should indicate that the opto-isolator is switching on and off? Is there a way to test the signal from U3 to the processor?

[Matt Cramer]

Sorry, I meant to ask to scope TSEL. What do you find there?

[71gto]

On TSEL I have a 1v square wave. It's not a perfectly horizontal peak. It's slightly arched. Maybe .9v to 1v arch. Not much. No noise. But the leading edge and trailing edge are sharp.
Also, I checked the path from TSEL to pin 14 on the daughterboard and it's a straight shot with no resistance.

[Matt Cramer]

If you remove the processor, does this change the voltage?

[71gto]

If you remove the processor, does this change the voltage?

No with the processor removed, I get the same signal I get on TSEL with the process in.

[Matt Cramer]

If R13 checks out and is getting 5V, this sounds like a bad optoisolator.

[71gto]

I checked R13 and the resistance is good and I have 4.98v on both sides. So I will go ahead and order a new Optoisolator. When I do get it replaced, what kind of signal should I be expecting on TSEL?

[Matt Cramer]

If you have 5 volts on R13 but not on TSEL, do you have continuity from either side to TSEL? One side should be connected there.

Or is TSEL not jumpered to OptoOut?

[71gto]

I checked continuity on both sides of R13 to TSel. One side is 4.7K and the other is 5K.

TSel is jumpered to OptoOut

[Matt Cramer]

Check for a burned trace or cold solder joint; R13 should go straight to OptoOut.

[71gto]

Okay, I made a mistake. I checked R12 for continuity to TSEL instead of R13.

I just checked R13. It is in spec and one side is a direct path to TSEL/OptoOut. One side of R13 has 5V and the other side is at 1.5V. That 1.5V is carried to TSEL without any drop. I was looking at a schematic for a 4n25 Opto Coupler (U3) and it looks like pin 5 would be the output of U3 to the processor? If so would I be looking for a 1.5V square wave on pin 5?

[Matt Cramer]

That's right. It sounds like the optoisolator isn't working right here.

[71gto]

So I went ahead and ordered new optoisolator. It should be here sometime next week. I did check my signal at the opto-isolator on pin 5 and it is a 1.5v square wave. Pin 5 is tied to pin 14 on the daughter board and TSel. They all have continuity between each other without resistance. Sorry if I'm just saying the obvious but this is my first go around with Megasquirt. It looks like the processor is getting the correct signal and just not recognizing it? (please let me know if I'm missing something). I'm wonding if a reflash could help or if I'm reaching for straws? I'm just hoping that the daughter board isn't bad. Is there any way to troubleshoot the daughterboard? I haven't found any internal schematic of the daughterboard.

[slow_hemi6]

Is C11 faulty and pulling the 5v down to 1.5?