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Today's Fuel Problems

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M

mallard

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This has been going on for a least 3 years now and is starting to become a pain. Took the car out for a breakfast run the other day down to the lakes, and stopped for a photo shot. The weather was is in the upper 80s at the time. Five minutes later and the car does not want restart. It kind of does but seems to be on 2 3 cylinders, I try to feather the gas to get it on all six, but then stalls. Open the hood, the embarrassing part, and BS with friends for 10 minutes and the car fires right up and runs perfect.

The fuel in Arizona is 15% alcohol this time of year. Does the heat that forms when you shut the car off for a short time make this cheap gas less volatile, and make for hard starting? Let the car cool and all is fine.

I like to keep my cars stock but I'm thinking I may have to install a heat shield. ARI or ARE not sure what the correct letters are for Joe Alexander.

The car is in good tune, and runs with the Petronix ignition.

Opps it's the red car I'm talking about.
 

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Sure sounds like fuel vaporization. A heat shield would be an easy and reversible next step.

BTW - sorry for being slow on responding. It took a couple minutes for me to stop staring at the cars and AZ scenery!
 
Seems to be the opposite problem, the gasohol boils easier and "percolates" raw fuel into the intake manifold. If you try to start the engine before it evaporates, it wets the plugs and won't run.

Anything you can do to keep the fuel and/or float bowls cooler should help. Lots of folks have had good luck using Joe's heat shields. An electric fan that runs for a bit after you shut the car down would help, too.
 
Nice TR6! Looks perfect. Nice picture by the way.
 
I had the same problem with my 1969 TR6. I live in
tropics. On really hot days the engine would cut out while driving. Vapor lock.

I installed an insulated carb bowl shield and never
had the problem again.

coolCarbs1.jpg


d
 
Percolation.
As long as the fuel is moving along, you shouldn't have a problem: but after it sits a while on top of a hot exhaust manifold, well, that's another story.
The owners manual suggest holding (not pumping) the accelerator pedal down 1/3 when cranking an engine that's been sitting hot.
It helps but it does take a while for the engine to straighten out after the percolation. Heat shield helps too, but I didn't find it completely eliminated the deal on the hottest of days.
 
I agree with all of the above. But give this a try. Go to a place where they have an air compressor (if you don't have one yourself) and remove the fittings or the rubber hose as in my 1958 TR3A on the fuel line just before the point where the fuel enters the fuel pump. Then open the fill cap for your gas tank and give the nozzle on the end of the air compressor hose a few short bursts of air so all the sediment in the fuel line will be sent back into the gas tank. You will hear the air bubbling back inot the tank.

I had these problems a few weeks ago and I tried everything. Since I blew the dirt out the fuel line back into the tank, I haven't had any more problems during the last 200 miles.
 
Just a thought : ISTR the TR6 has a tube that circulates hot water through the intake manifold, to reduce emissions in cold weather. You might try blocking off that tube and see if it helps.
 
Yet another random thought (yeah, I can't sleep); you should check that your float bowl vent valves are properly adjusted (so the vent to the carb face is blocked with the throttle closed) and that the vent through the carbon canister is open. The canister has a screen and filter inside that can cause hot start problems if they get blocked with crud and/or rust. The factory specified replacing the canister every 48,000 miles, but the early ones can usually be disassembled and cleaned. Any auto parts store should have a replacement for the filter (mine came from a 1980 Chevy Citation), which you can cut down to fit the Triumph canister.

Just to prove there is nothing new under the sun, here is a Popular Mechanics article from 1964 discussing percolation, vapor lock and possible cures:
https://books.google.com/books?id=RuMDAAA...p;q&f=false
 
Or you could drive and gas up in Iowa. I can get 91 octane straight gas at almost any stop, some claim 93. Don't get it though, we grow the corn for ethanol.
 
Thanks for all the great ideas. I will try them all this summer while the car is in hibernation.

Don I will clean out the lines as you suggested when I replace the filter, and check the rubber line coming out of the tank. The line is very close to the Stebro exhaust and crack after a short time . I did install some insulation around them last time so I hope they are still in good shape.

Randall I did not even think about the carbon canister. It was replaced with an NOS can 7 years ago when I was finishing the restoration, but you never know. The idea about the intake cross tube is also a good one. I think I will try to get some temp readings with, and with out it in place.

Richard I hope we can get back to growing corn for food or feed. I have to go to the airport to get some good gas around here and mix it. I don't like to handle gas that way though.

Thanks again for the ideas.
 
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