Triumph Repair: 1975 TR6 stalls when hot, lines tank, gas tank

Question
QUESTION: My 75 TR6 has run very well until recently. It starts well and runs great for about 10 minutes, then stalls and can't be restarted until it cools. I already replaced the coil, no luck. Any ideas would be greatly appreciated. Thanks!!

ANSWER: The Trio is Fuel, Spark, Compression.  If you have spark when hot, then it is not the electrics;

This sounds like a fuel issue; namely vapor lock; check the carb vents, and any emission lines connected to the fuel lines & tank.  See if there is a blockage that would not allow the system to breathe.

If that doesn't reveal any problems, then I would start working by checking fuel pressure, float level settings, and then tear down and rebuild of the carburettors..

---------- FOLLOW-UP ----------

QUESTION: Thanks. Replaced the compressor today. No change. Getting a good strong spark when hot. I removed the fuel line before the first carb and placed it in a jar. good flow when cool, but NO flow when hot. Does this mean I'm looking at a new fuel pump? What test should I perform next? Would a heat shield behind the carbs help? Any help is always appreciated! Thanks!!

ANSWER: Pop the gas cap (leave it open) and try that test again.  If it flows when hot now, then the gas tank breather is plugged/capped and the gas tank can't draw in the air it needs to replace the fuel you have pumped out.



---------- FOLLOW-UP ----------

QUESTION: Sorry, already did that as well. It seemingly had no effect and still conked out when it got hot. Anything else I can try?

Answer
If you have no fuel flow when hot, then the problem is in the gas line or the pump; is the pump mechanical or electric?  Where is it mounted?

If electric, can you run the line back to the tank, and let the pump just pump for a length of time; if it keeps pumping past the 10 minutes or so "hot" mark, then the pump is OK.  

If mechanical, can you manually pump it with the lever (if that type of mech fuel pump) when not flowing?

Trace the line that runs from the gas tank to the fuel pump; make sure it isn't too close to the exhaust.

Let me know what you find...