Triumph Repair: 76 spitfire, bright sun light, gasoline engines

Question
my spitfire will die while driving,if i turn ignition off then back on it start's right back up,otherwise it run's great.

Answer
Hi Glen,
The easiest car in the world to fix is a car that don't run. The hardest car in the world to fix is a car that don't run on occasions.

However, there is a method to catch what is wrong without buying a bunch of parts that are not at fault. This is a 100% effective method.

All gasoline engines require only 3 items to run.
1. compression
2. fire (Spark)
3. Fuel
With conditions on each item.
In your case one or more of the 3 went away but only for a short time so you need to see with your eyes which one/s went away.
Compression can go away but it will usually stay away and not come back so you can for now eliminate that one.
The end result in "Fire". (spark) Is the spark plug firing? The chances of 4 spark plugs failing at the same time and then returning is very remote so you can then just check and visually watch the spark to the plugs at the time of failure. This is easy to do and not expensive.
You will need a timing light and they can be purchased cheep. Unless you plan to go into business you will be ok with a cheep light (Wall Mart, Harbor Freight or such)
Connect the timing light to any plug wire or even the coil wire and tape the trigger down on the light so it flashes all the time. Run the wires out from under the hood and put the timing light under a wiper arm so you can see the light flash while driving. Be careful with the wires at the edge of the hood so as not to pinch the wires. If you intend to run this test in the bright sun light you may need to tape a cardboard cover over the end of the light so you can see the flash even in the bright sun light.
Then drive the car until it quits and note if the light keeps flashing on after the engine dies and is coasting to a complete stop. If the flash stops first then you have a primary ignition failure and you need to tell me so I can give you the next test.
If the engine dies and coasts to a stop with it still flashing all the way, then you have a fuel problem and you need to tell me so I can give you the next test.
Howard