Coil ve- Fuel Only (No RPM)

[carmaniac37]

Hey everyone, I've been struggling with this for a couple weeks now. I'm attempting to trigger an MS1 using either the tach output from the factory Bosch motronic unit or the coil negative terminal from one of the ignition coils on a dual dizzy setup.

This is on an Audi 3.6L V8. So far I haven't been able to get an RPM signal in Tuner Studio. I'm using an MS1 V3.0 and have done the internal mods as described in the manual and all other posts about fuel only. That includes installing R12 and R13, D1 and a zener in reverse position at D2, XG1 to XG2, OPTOIN to Tachselect and OPTOOUT to Tsel. I've attached an .msq and am hoping I have a filter setting of some kind wrong which is blocking out my signal. I have tried triggering off of both negative coils and the tach output from the bosch ecu which should be a 12v signal. I tried jumping D2 as well since a 12v signal wouldn't overcome a 32v diode. Everything else is working and I tested for continuity along the optical isolator circuit with success.

I did try to update the firmware to no avail saying could not connect to com port. I have been having cable issues though. The cable itself stops working when it gets very cold, such as in the garage for a while.

Thanks for any assistance!

[Matt Cramer]

Will it get RPM on a Stim?

[carmaniac37]

I successfully upgraded from 029q to 029y4 today. Ended up having to use the boot jumper. No RPM from stim. I also confirmed rpm signal from the coil and the Bosch tach output using an old school engine analyzer. Should I upload an updated .msq with the new code?

[DaveEFI]

The opto coupler input part is simply a type of LED. If you've been experimenting, it's possible you could have damaged it. Have you got a DVM with a diode test function?

[carmaniac37]

I can get my hands on a meter to do that. Is that U3 you're referring to?

[carmaniac37]

Sorry to double post. What exactly should I test with a Diode tester? This is definitely where my skills are lacking in the trouble shooting department.

[carmaniac37]

Just to come full circle on this. Turned out to be a broken connection inside the board between pin 2 of the U3 Optoisolator and XG1. This means the LED side of the optoisolator had no ground and was not passing the signal through. Soldered in a jumper from U3 pin 2 to the XG1 XG2 jumper. The car fired up right away.