Coyote run on - engine won't shut off

[TTimmy]

Hi Folks, Look for some pointers as I work to troubleshoot the following issue: I have a Gen 3 Coyote in a Coupe that will continue to run after the ignition switch is shut off. I have only run the engine a few times and it seems to occur after it has been running for a few minutes. The engine will shut off as expected until it runs for a few minutes. It is before the engine gets hot enough to start the radiator fan.

The Coyote PDB is wired hot at all times and the rest of the car electrical sits behind a master disconnect.

In order to shut down the engine while in the "run on state" I must turn off the master disconnect and remove the negative terminal from the battery.
As always, thanks again for your help!

[michael everson]

I would start by swapping the 2 large relays in the PDB one is for the cooling fan and the other is for the PCM. maybe its a sticking relay. You could also try pulling the relay when the problem is happening.
Mike

[TTimmy]

I think have isolated the issue to the RF side of things by installing a switch onto the light green Coyote "ignition relay trigger."

Once entering the "run on" state I can toggle that switch off and the engine shuts down. After shutting if off I check the orange RF ignition feed shows ~9 volts and I can watch it slowly bleed down. The accessory feed shows 0 volts.

Only thing on that I have on the accessory feed at present is the fuel pump and turn signals (and hazards). Guess I will poke around there for a while.

[michael everson]

That’s a strange one. Something must be storing voltage for a short time.
Mike

[Papa]

Could something on the BATT circuits be backfeeding power? The fan circuit, for example?

[edwardb]

Sounds like you’re zeroing in on the problem. As long as there is +12v on that wire the Coyote will keep running. So something is going on with the RF harness that is leaving voltage on the EFI wire even with the ignition key off. FWIW, any ignition controlled +12v wire can be used. On my Coupe, I used the RF choke wire. Works perfect. Maybe check that wire, if not already used, and see if it’s doing the same thing.

[michael everson]

There is really nothing in the RF harness that can store power. I wonder if somehow your alternator is back feeding the system.you didn’t connect the small brown alternator wire to anything right? It’s not used on the coyote.
Mike

[32J]

The first time I drove at night, returning to the garage with the headlights on, I turned the key to off and the engine kept running. I panicked. Then I realized my lights were still on, so I pushed the knob in to turn off the lights. The engine turned off immediately. I don't recall reading this anywhere in the manual, but it must be a safety feature of some kind to let you know that your lights are still on!

32J

[TTimmy]

Thanks for all the input folks!

I took a break today to hike with the dogs, watch some F1 and attend a car show. I will be back at it tomorrow.

The plan of attack will be a process of elimination... I will pull work through pulling fuses to determine the cause of the unexpected voltage. While it manifested itself first with the engine run-on, clearly something else is incorrect.

Stay tuned - I will report back my findings.

[TTimmy]

Once isolating the residual voltage down to the turn signal circuit I found the source to be the LED flasher module. I tried swapping the turn signal and flasher modules but had the same result. If I remove the module and jumper the connections (eliminating flashing from the circuit) I have no issues whatsoever.

A capacitor is clearly visible within the United Pacific LED turn signal module and seems to be the source of the residual voltage.

Thus, I am wondering if I have two bad flasher modules (unlikely?) or if I have miswired something. I have tested the flasher module ground as good.

[Papa]

You are getting power feeding back through this circuit. You could install a diode on the turn signal wire(s) to prevent the power from back feeding.

https://www.amazon.com/gp/product/B011NMG160/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

[TTimmy]

Papa, you are right - I validated that placing a diode between the flasher "12 volt input" and 12v source resolves the situation. I find it odd that the flasher mechanism does not include the diode internally. In order to resolve my issue, as I currently understand it, I would need to wire the diode between the flasher input and the 12v source on the fuse block... while doable, it's tight in there and a pretty short span of wire.

I have removed the flasher once "charged" and confirm that it is holding 12v between it's input and ground.

I wonder if I am missing something else as I don't see other folks having to deal with this issue.

[michael everson]

I have never heard of this in all my builds. Probably close to 20-30 utilizing those flashers and a coyote. Very strange. Maybe try buying new flashers. Maybe even a different brand.
Mike

[Papa]

What are you using for your turn signal switch?

[TTimmy]

I ordered a different brand of relay, thought it looks the identical and is probably from the same factory. Worth a try for 12 bucks.

I'm using a Russ Thompson setup for my turn signal but have eliminated that as a cause. I disconnected the RT setup, front and rear harnesses as well as hazards while troubleshooting. Eventually I got to the point of simply energizing the relay and found that it was holding voltage once the supplied power by the ignition.

Frankly I don't mind the troubleshooting. It's all part of the fun and helps build a deeper understanding of how everything works. If this was easy everyone would be driving one of these!

[Ducky2009]

The RT turn signal instructions say to install 3 diodes, but if you have the two individual indicator lights, either in the speedo or individually mounted in the dash, you only need one. If you can't find the correct diode, let me know. I "think" I have a few extra, just need to find them.

Not sure if/how not having diodes would effect your issue.

[TTimmy]

This issue has been resolved and for the benefit of those that follow I will share my bonehead move. Thank you to everyone that provided help along the way!

In short, I misunderstood the instructions for connecting the coyote fan to the Ron Francis harness. I must own this mistake; the instructions and forums are quite clear on this matter. While I should have connected directly to the blue wire on the fan side of the fan relay, instead I connected to the green thermometer wire. This resulted in power remaining on the ignition feed after shutting off the ignition switch if the engine was calling for the fan to run. Thus the engine continued to run.

The fan relay is connected to that "ignition bank" within the fuse block. Seems that this supplied the voltage necessary to keep things running.

[Mastertech5]

Remember that for your next build! If you have AC that one goes to the green wire.