Ignition continues running with key out for short time! (3 Viewers)

[Mercedes Tristar]

When I turn the ignition off, I can remove the ignition key and the engine continues to run for approx 15/20 secs.

Engine runs fine at all times, it is just when we switch off, I could still drive it for the short time mentioned above with the key!! Any thoughts on why this is happening, please.

 

[Pausim]

I had this with one motorhome but only when I had a trailer attached. The engine solenoid was getting a back feed from the trailer brake lights.

 

[DBK]

What mileage has the engine done?

 

[Jev88]

On old cars it was diesel fuel pump solenoid sticking or badly carbonised cylinders that glowed enough to ignite petrol.
Eg if you bypass the very old Fiat immobiliser and don't run to accessory only live to he engine never stops until you disconnect the new feed.

 

[Two on Tour]

I had this on our Peugeot Boxer MH when I fitted a new radio head unit and connected the steering wheel radio controls to the wrong CanBus line, swapped to the correct CanBus line corrected the engine overrun when switching off the ignition.

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[Reallyretired]

My first diesel coachbuilt back in the 70s used to regularly do this
It was a very agricultural diesel and the only way to stop it sometimes was put in 4th gear, stand on the brakes and stall it.

 

[jockaneezer]

Does sound like an issue with the fuel cut off solenoid. If you're mechanically minded, it will be located near or on the injection pump. Check out the wiring/connector to it for signs of corrosion and also check out the condition of any earth straps from the engine to the body work.
A quick earth check would be to clip a jumper cable from the battery negative to a clean metal point on the engine and see if that helps ?