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Old 03-27-2010, 03:58 PM   #1
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Default 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?
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Old 03-27-2010, 04:15 PM   #2
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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.
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Old 03-27-2010, 04:19 PM   #3
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Quote:
Originally Posted by Ben View Post
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.
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Old 03-27-2010, 04:21 PM   #4
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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
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Old 03-27-2010, 06:19 PM   #5
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bad ignition switch?
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Old 03-27-2010, 06:28 PM   #6
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Quote:
Originally Posted by Ben View Post
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.
His MS only gets power from 4AF, so +1.

Jim
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Old 03-29-2010, 04:09 PM   #7
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Any chance the power is back-feeding through a relay?
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Old 03-29-2010, 04:24 PM   #8
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A friend has this problem too. But when he turns the car to run computer turns off.
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Old 03-29-2010, 09:37 PM   #9
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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....
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