MS stays powered up with key off
 

It happens once in a while. Cannot figure out what may causing this.
Anybody else had a similar issue?

The MegaSquirt ECU does not need a full time powered +12V source, and should not be connected to one. Power up is soley commanded solely by a switched +12V in. If your ECU is not shutting down it is because your switched +12V is not depowering when you turn the key off.

But it is powered from a switched +12. The same +12 that stock ecu gets.

This is not happening all the time. It happened today. Last time I remember happening was 2 weeks ago and then it was gone until today.

Forgot to mention that when this is happening, if I disconnect the main ms harness and then connect it immediately it remains off.

EDIT: From Peter Florance 2009 presentation:

• MS stays powered up with key off.
– Injectors or idle valve not connected to same
switched +12V as MegaSquirt box

bad ignition switch?

His MS only gets power from 4AF, so +1.

Jim

Any chance the power is back-feeding through a relay?

A friend has this problem too. But when he turns the car to run computer turns off.

and both those symtoms make me still wanna say the ign swtich, my radio used to stay on once in a while, along with something else i forget, but one day the car finally didnt have the start position, and i had to jump it to get to work. but i took apart that switch and the contacts were all begining to melt and just look shitty, so its worth a look....