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- #661
Idle is at 900rpm because of my Delta cam.
But … I figured this out finally last night and it’s a weird one. I was kind of working off a gut feeling and ideas started coming to me. The last thing I did before the dieseling started was change the alternator Tuesday night. I never went for a test drive, I just drove to work Wednesday morning and that’s when the problem started - the first time I shut the truck off after swapping the alternator. The one I removed and the one I installed are both FJ80 units, but one was Rock Auto and the other Toyota. They have different plugs on the back, neither of which are the 2-pin connector in the 2F engine bay, so I had originally wired up a pigtail adapter with parts from Coolerman. When I changed alternators I had to de-pin the connector for the Rock Auto unit and repin into a different connector for the Toyota unit.
Of course I did that incorrectly. I missed the part of the 80 Series EWD where it says the pictures of the connectors and their pinouts are looking at the business end of the connector. I had assumed it was looking at it from the back, hence putting the pins in the wrong locations. I corrected the pigtail adapter last night and boom - no more “run-on”.
I have two theories:
1. The wrong part of the alternator was getting energized and actually providing rotation force after shutdown (I.e. somehow the stator was making the rotor turn instead of the rotor being spun by the belt and inducing a voltage on the stator). The alternator was providing rotational force on the belt which made the crank turn. Once one piston got to the top and squeezed fuel vapors it was hot enough to ignite, kicking off a chain reaction of other pistons compressing and firing.
2. Somehow the incorrect wiring was providing 12V on the wrong side of the ignition switch. The side of the switch that’s supposed to have 0V when the key is off was getting power, which provided power to the coil, igniter, dizzy, and spark plugs. This technically wouldn’t be considered “dieseling” because there is a spark ignition source for combustion, and it’s not happening purely from compression alone - better to call this one “run-on”.
Here’s what the pigtail is SUPPOSED to be doing:
Rather than having the jumper from the keyed ignition voltage source to the sense contact, I think I had originally wired it so the sense and charge light contacts were jumpered together.
@ToyotaTechnical
@POTATO LAUNCHER
@RodrigzCrzr
All provided me tech support last week before I chased this wild hunch. All are fine gentlemen.
@RDub I know you like weird problems and their solutions, check this out!