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TR6 Engine bogs down and backfires after warm up and under a load

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C

CFIITN

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I’m new to this forum and am not a mechanic, but I purchased a 1976 TR6 new and still have it. I basically changed the oil, rotated tires, flushed radiator and installed brake pads. The car has a little over 76,000 miles. 5 years ago while driving at highway speeds, it began to sputter and backfire. I pulled over and let the engine cool, restarted it and limped home. Parked it for 5 years due to life issues and now am trying my best to get it running as it should. To date I have had a local mechanic replace the fuel pump and filter, install new coil, new spark plugs, new spin on oil filter, added electronic ignition, tuned the Stromburg carbs, installed a heat shield between the the carbs and manifold, wrapped fuel lines with insulation, flushed the radiator and now I’m told we may need a new fuel tank which is on back order at Moss and TRF. I have read through the threads on vapor lock and think that’s not the problem. Any ideas are welcome and I thank you in advance.
 
Don’t see that you replaced the distributor cap, rotor or wires.
You might take a look at the inside of the distributor cap and inspect the rotor and the small carbon “button” at the top center of the cap. The carbon button should not be broken.
 
Gliderman8 said:
Don’t see that you replaced the distributor cap, rotor or wires.
You might take a look at the inside of the distributor cap and inspect the rotor and the small carbon “button” at the top center of the cap. The carbon button should not be broken.
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Thank you for bring thorough! I did change all the wires and plugs and converted it to electronic ignition.
 
CJD said:
If it backfires out of the tailpipe, it is ignition problems. If it backfires out of the intake, then it is a lean condition.
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Thank you! That is helpful and helps me feel more confident about getting the fuel flow adjusted. Leaning now towards installing new fuel tank.
 
Has anyone checked the diaphragms in the carbs ?
ZS carb torn diaphragm 006.jpg
 
Here's another consideration since you've converted to an electronic ignition. Your '76 used a ballast resistor built into the wiring to feed the coil. You should'nt use the original positive terminal wire for the coil in this case, rather you should disconnect the original wire going to the + terminal on the coil and run a new wire from the fuse box to the + terminal in order to bypass the ballast resistor.
If you used the original wire to feed the coil, it may well be that the coil is operating at too low a voltage to function reliably. Use a terminal on the fuse box that already has white wires connected to it, these will be switched off and on by the ignition switch.
 
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