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Triumph Repair/TR6 won't start after driving

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Question
I have a 1974 Triumph TR6. Starts fine, runs good. After driving, if I stop and turn off the car, when I come back it won't start for around an hour. Then it will start and run fine. If I stop again, same thing happens. I changed fuel filters twice. It has an electric fuel pump.

Thanks

Mike

Answer
Hi Mike,

There are only three things to stop an engine from starting. Compression, Fire and Fuel. You have to test which of the three is failing at the time of the failure.

Compression will not come and go. If compression is lost it will not return so your problem is either Fire (Ignition) or Fuel. Both of these can come amd go. Fire must be tested before fuel.

Fire is easy to test but must be tested while the engine is in it's failed mode (not starting)

If you have a timing light put it on a plug wire and have someone spin the starter and watch for a flash of the timing light. If you don't have a timing light remove one spark plug or use an extra spark plug to place on one of the spark plug wires and spin the starter and watch for a blue spark (not in bright sun light)  the spark must be blue in color and as thick as a pensil lead. If you see a hair thin spark colored orange or yellow then the spark is too weak to start the engine.

If when the car will not start, you have a good thick blue spark then and only then should you test for fuel. This is also easy. Get a spray can of starting fluid from any auto parts store and when the car will not start, spray the starter fluid into both air filters and then try to start the engine. If it starts but will not continue to run unless you continue to spray starting fluid into the air filters then you have a fuel supply problem and must test that with a fuel pressure gauge connected to a "T" fitting at the fuel line at the carburetors. Be sure to get hose clamps too, when you get the fuel hose and the "T" fitting. These are not expensive and can be purchased at any auto parts store.

With an electric pump in place of the standard mechanical pump normally on a TR-6 you should see from 1.5 PSI to 3 PSI on the gauge as soon as you turn the key on. If you see more then 3 PSI then the wrong electric pump was installed. And the engine is most likely flooding with too much gas. If you see less then 1.5 PSI it is starved for fuel.

Let me know what you find. Don't toss any more parts at the problem until you have made and ID of the failed part.

Howard  

Triumph Repair

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Howard M. Fitzcharles III

Expertise

Triumph TR-4 up & Spitfire, and Engine theory

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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