TR2/3/3A Engine does not shut off right away. Why?

[Momikey]

Hello,
So I know this is a common problem with lots of cars but what is the cause?
When I turn car off engine runs a little bit then shuts off.
Is this a timing thing? Or more to do with carb adjustments? Or what?
Thanks.

 

[bobhustead]

Excess heat or excess compression (carbonized combustion chambers) can cause the engine to diesel (i.e., ignite fuel without spark). Excess idle speed can exacerbate the problem. Higher octane can ameliorate. When the switch is off, timing is no longer relevant (no spark). If mistiming is enough to contribute to excess heat it could contribute to dieseling. Fuel mixture on the rich side will help cool the combustion chambers, lean to "hotten" chambers. Less likely, wrong plugs can store high heat and set off compressed fuel.
Bob

 

[Momikey]

Excess heat or excess compression (carbonized combustion chambers) can cause the engine to diesel (i.e., ignite fuel without spark). Excess idle speed can exacerbate the problem. Higher octane can ameliorate. When the switch is off, timing is no longer relevant (no spark). If mistiming is enough to contribute to excess heat it could contribute to dieseling. Fuel mixture on the rich side will help cool the combustion chambers, lean to "hotten" chambers. Less likely, wrong plugs can store high heat and set off compressed fuel.
Bob

Thank You Sir.

 

[Deleted member 8987]

The only thing I would ask is does it just run on a bit (smoothly...well, as smoothly as a TRactor can run) or jumping around and coughing like a 1912 Marmon?
If it runs just like it did before you turned the key off.....seen that a lot over the years.
If you have an aftermarket cooling fan on the radiator...and not relay controlled via the distributor wire off the ignition switch...and the fan is running...you turn off the key, the fan then becomes a generator, having energy in the spinning blade, and the car will keep right on running as it was for a specific period of time before the voltage output of that fan gets low enough there is insufficient spark to keep going.

 

[Keoke]

Very good info "TDC"---

 

[DougME]

A quick "fix" is revving the engine prior to turning off the key. Then immediately turn off the key while holding the throttle open. The mass of cold air sucked in then cools down all the hot parts and the engine will stop without dieseling.

Doug
'64 TR-3B

 

[sp53]

Built up carbon is glowing red hot and igniting the fuel causing the motor to run on. I have seen them go 20 to 30 seconds

 

[Frank_D]

I have had this problem for some time as well. Rebuilt engine, slightly hotter cam, 89 mm pistons and rebuilt carbs. I do what Doug suggested and it works every time. I think my issue is compression and not getting 94 octane on a regular basis. Try the rev and open throttle; it works for me.

Frank D.........

 

[sp53]

I was taught that if you accelerate the engine and shut the key off to stop pre-ignition the unburned gasoline would go into the oil and contaminate the oil thus the oil needed to be change frequently. Mover, this unburned fuel would wash out the oil rings and wear the cylinders out sooner.