rusefi.com

from discussion on discord:


5vp does not light up with just 12v below a certain battery voltage, causing a no-start condition

this was traced down to a severe enough drop at the main 5v regulator that would cause the main MCU to power down, aborting enabling 5vp, entering a loop.

fix is rather crude, but it's to force 5vp to initialize forcefully, MCU or not.

10k resistor between pin 7 and 5v rail, like in the picture.

gurov wrote: ↑

Thu Apr 11, 2024 10:30 pm

this was traced down to a severe enough drop at the main 5v regulator that would cause the main MCU to power down, aborting enabling 5vp, entering a loop.

We still do not know real root cause right?

Similar looking boards one would work another would not, right? https://github.com/rusefi/uaefi/issues/59

correct, still don't know the actual root cause, just breadcrumbs of symptoms with comparison to good board

Not to necro an old thread but this might still be the case. Have a UAEFI hooked up to a bench power supply putting out 12v with nothing connected besided power and ground and it appears the 5v rail isn't firing up. When I plug in the usb to a laptop the 5v rail stays up even when removed. I don't have a variable power supply but it looks like even as low as 12.2 and I don't see it kick on. Can be a bit inconsistent though. I have had a case where I know the battery was low and the 5v line fired up fine, enough to bump start and get the generator spinning but not enough to use the starter.

See also https://github.com/rusefi/uaefi/issues/85

Anche la mia uaEFI personalizzata aveva il problema discusso in questo post
Per risolvere il problema ho eliminato R141 e aggiunto R142 nel modulo mega-mcu-100
con questa modifica funziona perfettamente.

non sò se è la soluzione corretta, non ne ho trovate altre.