BN7 tri-carb will not start

[66ejag]

My BN7 will not start if the engine is warm, i.e., temperature above 90F. However, it will start easily when cold if choked and released immediately. Even though it runs satisfactorily once started, I am reluctant to drive since it takes several hours to cool down sufficiently if I stop. I checked the carb floats and they appear OK. I'm baffled.

Thanks and have a good day,
Ed

 

[Keoke]

Hi 66ejag, do you have the automatic choke on your tricarb?

 

[66ejag]

Keoke,
No. Hand choke.

Ed

 

[RonMacPherson]

Just for kicks, next time the hard starting hot occurs, open the gas cap and see if it starts.

 

[AlanT]

Two big Healeys acted as you describe this past weekend at the show. One was a coil breaking down when hot and the other was a condenser shorting when hot. Both would restart after cooling for a while. The carburetors were the first suspects of course. But then someone remembered the age-old rule...'Most carburetion problems are ignition'

Alan T

 

[healeynut]

Ed -

That is a classic symptom of either a bad condensor or coil.

Check for spark when the car is hot and see if the dizzy is sparking at the plug. If not - coil or condensor.

 

[66ejag]

I replaced the coil with a used spare that I had. I also regapped the ignition points which were almost closed, a condition which I can not explain since the bolts were still tight. However, the Healey now starts at any engine temperature.

I intend to buy a new coil but would like some recommendations, e.g., original type or higher voltage type. My dizzy is original.

Thanks again to everyone,
Ed

 

[Dave Russell]

Hi Ed,
It could have been the coil or the points or both. Most likely the points.

Depending on point brand & construction, the rubbing block (part on the movable contact that contacts the cam) can wear rather quickly which closes the gap, retards the ignition timing, & can cause a weak spark.

The distributor cam should be polished very smooth & a distributor cam lube helps reduce the wear rate. You still need to check the gap frequently & reset it if needed.

A higher voltage coil will only be a benefit "if" the plug gaps are increased. If the plug gaps are increased very much, it may cause the insulation of the rotor to fail. Quite a few rotors seem to fail anyway. The old Lucas cap & rotor design was just not up to handling higher voltages very well.
D