[TR] Dieseling

[Randall]

> Hoo boy.B  I've been reading archives until my eyes crossed 
> trying to find a consistent answer about how to stop an 
> engine from running on.

I don't think there is a consistent answer, or even a consensus.

> One suggestion was carbon deposits.B  This could be, though I 
> run at 3800 RPM's for 30 minutes every day.

Modern fuel leaves much harder deposits than the old leaded stuff did.  I
don't know what all is in there, but it's not just carbon and it's much
harder to remove than the old stuff was.

> Besides, ISTR that consensus on the List was that these cars 
> were meant to run on regular?

I guess I'm a dissenter, then.  "Practical Hints" states only Premium fuel
of 95 research octane or higher.  Of course in the US they only publish the
average of research and motor octane (RON+MON/2), but assuming the
difference is about 10 points (as per Bruce Hamilton's Gasoline FAQ), that
means you want fuel with an advertised octane of 90.  Even Premium around
here is usually only 89.

> And yet another suggestion was that the butterflies weren't 
> closing completely.

Which of course would also cause high idle rpm.  Getting the idle rpm down
low will definitely help prevent run-on (but may also make the engine tend
to die after sudden stops).

> I'll stop 
> now and solicit any thoughts that might put this thing to rest?

FWIW my TR3A started wanting to run-on sometimes; not too long after leaded
fuel became unavailable.  This problem has persisted, occasionally, through
may other changes.  I've been living with the problem, by 'killing' the
engine with the clutch just as it should stop anyway.  Leave it in gear,
foot firmly on the brake, and let the clutch out just as the engine should
stop.  It is possible that there are adverse effects from this; but I've not
seen any in almost 20 years of doing it an average of twice a day.  Never
even wore out a clutch plate (tho it has been changed for other reasons).

Other steps that should help with run-on:
1) Lower the idle rpm.
2) Switch to a colder spark plug
3) Remove the cylinder liners and clean out all the crud that accumulates
around #4.
4) Radius all the sharp corners in the combustion chamber.
5) If all else fails, it shouldn't be too hard to add a anti-run-on solenoid
from a later TR6.  Have to drill & tap the filter head to mount the oil
pressure switch; drill & tap the intake manifold for a vacuum source; and
add a relay to provide the "normally closed" contact from the ignition
switch.  Then it's just a matter of mounting components and running hoses &
wires.

HTH
Randall