Hi all,
I've been struggling with some engine run on issues (remove key - engine keeps running). I thought I would post what I've learned and hopefully help someone else with similar issues.
I installed an aftermarket engine management system. This eliminates the CDI box and CIS. After the install I started having issues with engine run on where I would remove the key from the ignition but it wouldn't stop the engine. Of course this is not ideal..
What I believe happens in a normal vehicle:
-Key into ignition: wakeup signal (12V) to engine components driven by the ignition circuit
-Engine starts and alternator begins charging
-Key off - ignition circuit open (slight backfeed from the alternator isn't enough to keep the CDI box awake) so the ignition system stops and engine shuts down
What I believe happens in my vehicle:
-Key into ignition: wakeup signal (12V) to engine components driven by the ignition circuit
-Engine starts and alternator begins charging
-Key off - ignition circuit open -slight backfeed from the alternator
IS enough to keep my ECU awake and engine keeps running.
My solution, as many already know, is to place a diode in the alternator excitation wire. This prevents backfeed which keeps the ECU awake.
Does this seem reasonable to everyone? Anyone have a similar issue? I searched and searched but couldn't find this straight answer elsewhere.
