I have have had an engine run-on issue that has come and gone on my car. It went away completely for about 2 months and just recently showed back up. About 50% of the time the engine shuts off with the key, the other 50% the engine will continue to run. Sometimes I can turn the key on/off several times and it will die, sometimes that doesn't work. It's very inconsistent.
When the engine runs-on my ECU is seeing 8.0v, somewhere I am getting a backfed source of power that is knocked down from the battery. I verified that by powering the voltage regulator with the engine running on and the 8.0v went up to 9.5v.
What I know:
*When the engine is running on*
- 8.0v to the ECU and control side of fuel pump and inj/coil relays
-Engine will run "forever" in this state, the 8.0v is knocked down from the battery. Somewhere.
- I can pull the main relay, car still runs, see note in attachment.
- Sometimes I can toggle the ign switch on/off and it will die.
- I have completely disconnected the ignition switch, it has nothing to do with the issue, from what i can tell
- It typically happens after the engine has been idling for 1+min
- If i pull the 20a inj/coil fuse the engine will die [obviously], but the 8.0v *goes away* and the ECU will go offline
-If I pull the fuel pump relay, the engine runs itself out of fuel [on 8.0v]
- I can rev the engine and it will die
- I can open the alt charging circuit to the battery, it has no effect. I have not removed alt field wires, the field is divorced from the rest of the car with the key off. [no charge light]
I wired up the car completely from scratch and I like to think that I am pretty savvy at wiring. This one has got me baffled!!!! For now I have worked around it with a tableswitch with RPM and battery voltage <9.0v. But I hate having to do that.
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