MS3X injector circuits
 

Hi there, can anyone please let me know what voltages should be present on the MS3X injector outputs, if everything works correctly?

Took race car to Thunderhill last weekend - car ran fine for one lap, then engine started to cut out and eventually stopped working - wouldn't start at all. We traced the problem down to injectors not firing. Wiring between ECU and injectors checked out fine, rpm was present and crank/cam sensors registered without sync issue. Voltage measured on injector outputs was less than 1V and fluctuating, so we are assuming that somehow the MS3X injector driving circuits went out / got damaged. Does that assumption sound reasonable or are we missing anything else, here? We also found that one of the belt pulleys had eaten through the crank sensor wiring protective sleeve and exposed a bit of the black wire going to the cam sensor, so there's a chance that that black wire made contact with engine ground via the belt pulley - could that potentially have damaged anything inside the ECU?

Thanks much in advance.
Cheers

Injector outputs are grounding outputs. So the MS3x pulls the injector to ground. 1v sounds reasonable without a load.

Really you need to get a scope on the output and see what its doing.

Ok, thanks. We measured only around 9V on the injector common supply while cranking - is this too low for them to fire?

Not sure. You can always use the MS3 injector test mode to see if they are working.

What should the voltage on the MS3X output be with injector connected ?

Is there anything else that we are missing that would keep the MS3X from firing the injectors (other than rpm and crank/cam sensor sync)?

Post log and tune.

The voltage supplied to the injector is NOT from the MS. It comes from the main harness/main relay/ignition switch. If you have about 9v while cranking at your battery and 9v at your injector + side, I would say you have a weak battery.

If you have 9V on one side and 0-1V on the other, then your injectors are firing. The battery is not the greatest, but it doesn't seem like an MS problem.
When you say you traced the problem to "Injectors not firing", how was that determined?

Maybe it's a fuel pump issue?

Fuel pump is brand new (less than 2 month old), but we took it out and checked it anyway, but couldn't find any issue - we also replaced the fuel filter just to be sure. Fuel pressure gauge in the engine bay was reading a constant 40psi. The engine would start right up when we sprayed some brake cleaner into the intake, so it was clear it didn't get any fuel. Since we had eliminated most of all other typical reasons for not getting fuel, injectors not firing was the last remaining plausible clause (we didn't take the intake off in order to get the injectors out, though) .

where's the log file?

I'll have to check. Not sure if we had logging turned on since the MS3X had been running like clockwork before.

Turns out that we have some log files on the SD card, but they are all in ".ms3" format. Seems like MegaLogViewer HD is unable to read the logs in this format directly off the SD card. Is it possible to convert the logs to a format the MegaLogViewer can read? The MS3X is out of the car so not hooked up to 12V power.

Tuner studio has an option to import/convert datalogs from ms3

MS3X SD card log files
 

Here are the last 3 log files from the SD card in our MS3X. Please let me know if you can identify anything that would prevent the injectors from firing.

Thanks much in advance.