MicroSquirt.com read only forum (Jan.15,2018)

I have been working on tuning the last couple of nights, everything been good. Until it stumbled then shut off. Started it again not as quickly as usual. Ran for a little while then same thing. Looked at Megatune and noticed no rpm. Also fuel pump only runs now when you first turn the switch on. Will not run while cranking. It's a aircooled type 1 VW with fuel only hookup running Msd dist and box seperatly. I had to use a tach adapter before with my innovate datalogger. So used it again and hooked the signal wire to Pin 30 Optoin+ and grounded Pin 31 Option-. Worked good for about a total of 1 1/2 hour run time. Checked spark per Msd instructions good there. Pulled ampseal connector checked for negative flashing signal while cranking, good there. Checked connections grounds etc. Pretty much overkill on the wiring. While cranking nothing fluctuates but the map signal. Everything else reads good. Tried loading different msq nothing. Did i fry something internal. Any thoughts would be appreciated. Thanks Ken.

Sounds like the CPU is not getting a tach signal that it can recognize.

You may want to try the tach tester tool from this thread: http://www.microsquirt.com/viewtopic.php?f=89&t=23001, to see what the CPU is seeing for CPS/tach signals, although I don't know whether this tool is valid for non-decoder wheel setup.

What is the source of the signal that feeds MSD? Could you connect that signal directly to Microsquirt?

Cheers,
Paul

The funny thing is, it was working just fine? The tach on Megatune looked fine no spikes jumping around on anything. Last night was the first time i got it to idle good and that was the longest i let it run. I'm afraid something got over heated and burnt up. The ignition still works fine, will run on starting fluid. Is there any specs on checking the pins on the microsquirt for resistance etc. Too see if something did go wrong? I cut the signal wire too pin 30 It flashes negative while cranking, also shocks you? The Msd dist is a magnetic pickup. Someday i would like to wire through the computer to control it, just right now. One battle at a time! I was hoping too put the intercooler pipes on and hook up the wideband this weekend. Looking for any help.

Magnetic pickup as in Hall or VR? If it's VR, then I'd try connecting it directly to the VR1 inputs on 32 and 33.

Is the signal from MSD that you're using an output designed to drive a tach or is is the coil drive signal? If it's the coil drive signal, then doesn't that have the pulse multiplication that MSD stands for?

I think its a vr sensor,. I can check later and find out. I don't want control the ignition right now with the MS. Can i use that for the rpm signal? If so i will try that. There is a tach hookup on the side of the MSD 6al box. Which sends a crazy signal that most tachs must use the tach adapter to clean it up. Which i have installed and was working fine. I would really like too know what happened that it stopped reading what previously had?

You can use the VR signal for RPM info even if you're not using Microsquirt to run ignition. There will still be ignition output signals and a tach signal being provided by uS, but that's OK... just leave them disconnected.

No idea why things would have stopped working just like that. Are you sure there's nothing else that changed in the system?

Unless something happened to the Msd tach adapter. Appears to be working ok. I don't have access to another one other then spending $50 and ordering it. To use the vr do i need to change anything in megatune setup? Was running stalled then thats it. It's a nightmare to remove my MS and open it up. Maybe i would see something on the board? One step forward two steps back. What a learning curve this has been

You don't need to change anything in Megatune (should be set to no dual spark and no trigger wheel), just change the input wires used to the coaxial pair.

The basic test will simply be to see whether spinning the distro makes uS run the fuel pump a bit. If it does, then you know you're picking up a tach signal of some sort. From there you may need to play around with rising edge / falling edge and/or swap the signal and ground connections to the VR input. You may also need to add a series resistor if you find that this setup works but loses tach above a certain RPM.

I tried using the vr sensor no luck there. Then i thought why not just put a stock dist back in. Hooked it up checked signal with test light looked good. Still shows no rpm and will not turn on fuel pump. The pump cycles like it should when you first turn the switch on. I can't imagine the signal all of a sudden just went bad. I must of started it a hundred times before this happened. It was running then just shut off. Could something be wrong inside? I opened it up and didn't see anything noticeable. Is there someone that can check and repair this thing? Thank you for trying to help.

After hours of research i decided to build my own tach adapter. Didn't help. I read about putting a 50v 1a diode inline with the tach signal wire. Success that fixed my problem. Why it worked with out it at first i don't know and don't really care. I found the info on the MSII board assembly guide. I wouldn't think that stuff would apply to the Microsquirt being that it's pre assembled, but i got too remember it all works in the same way and same problems