Message text written by "John A. Simmons"
>What is the cause of engine runon when after switching the ignition off?
Or
is it something I need to learn to live with?
<
This is typical of the higher compression model TR6's. It is caused by the
combination of the compression ratio and hot spots in the cylinder head.
The casting rough spots and high points tend to get hotter because they
don't get cooled as well as the main body of the head casting and can cause
the fuel/air mixture to ignite in spite of the fact that the spark plug is
not sparking. To aleviate the problem you can remove the head and using a
small grinder (eg: Dremel) remove any rough edges and high points (don't
get carried away).
Another approach is to get some carbs and the anti-run-on valve and
canister from a later model TR6. The anti-run-on system connects the float
chamber vents to the chaecoal canister which, in turn, is connected to the
anti-run-on valve. This valve is normally in a position where the canister
is vented to atmosphere but when you switch off the valve is activated
momentarily and the canister is connected to the vacuum at the intake
manifold. This vacuum will pull the fuel away from the jets starving the
engine and eliminating run-on. Oh, BTW, you will also need a keyswitch and
an oil pressure switch from a later model car as well. And the wiring. (I
did this but with some custom circuits and wiring)
The other thing you can do is just before switching off put the car in gear
and ease out the clutch until the engine speed starts to drop. Then switch
off and let the clutch out slowly and the engine will not run on!
Dave
71 TR6
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