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Vapor Lock

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Dudly

Dudly

Jedi Hopeful
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Hi all, had a rather strange thing happen this weekend. The wife and I were about to head out of town towards a car show about 50min away. Rather hot day, upper 80s and mostly sunny. Had less than 1/8 tank, sooo decided to get gas before we left so I filled up the tank. Not but 50 feet from the gas station, the spit just died. I had spark and thought I had gas at the carb. She would fire up for a split second but not stay fired. I had been running around in stop and go all morning so the motor was plenty hot. After a nice relaxing lunch and a couple pints, the spit fired right up and ran great the rest of the day. Wife speculated that it was a combo of Vapor lock and the cold gas that I had just bought. I think she is right on the money. Anyone have any other suggestion.

Thanks, and have a great holiday.
D
 
Just my best guess.... You ran out of gas. It just took some time to prime the pump again.
I don't think those gauges are too accurate at all. Not sure I would trust that it had 1/8 tank. As I said, just my guess.
 
Dudly said:
...Wife speculated that it was a combo of Vapor lock and the cold gas that I had just bought. I think she is right on the money....
Click to expand...
I think your wife's a "keeper"! :smile: In other words, I think she was absolutely correct in her diagnosis. Had the exact same thing happen during my trip from NY to MN in 2002. Filled the tank on a very, very hot day...and couldn't restart. It had run fine to that point. I was fortunate in being able to "bump-start" it on a slight downhill grade...and it ran fine from then on.
 
Thanks everyone.
Once again I think your right on Andy, both with the Spit and the Spouse. Wifey's a smart cookie, not to mention she knew exactly what to do, find a cool place to eat, and just wait it out. If she weren't there I'm sure I would have sweated it out in the Rite-aide parking lot with increasing frustration, and blood pressure.
 
I have similar problems re-starting my TR3 after a short stop when the engine is hot. However, once I manage to re-start it runs fine. This modern fuel has a tendency to vapourise.
 
FWIW, ARE is offering a line of heat shields to fit TR3-6, that reportedly help considerably with hot starts, as well as improving both power and fuel economy.
https://www.the-vintage-racer.com/webroot/Heatshields/

I've got one myself but haven't had a chance to try it out yet.

If he could be convinced there is a market, Joe would probably offer them for Spits as well.

Another solution might be a muffin fan or two (from an old computer), with a thermostat to make it run whenever temperatures in the area are over say 200F. Chrysler used this solution on their minivans for awhile, just before they converted to fuel injection.
 
I believe the spit in question (Dudly's 79) has a factory heat shield installed already. Suppose they may have been aware of the vapor-lock issue back in 78, eh? its a funny little flap of steel upholstered in some sort of Asbestos carpet on the manifold side.

I'd take a bet itsa combo of an empty tank and the dreaded vapor-lock.

You should check the ethanol % in the gas you used. For instance, I have read that PetroCan has up to 25% ethanol content in all of their pump gasoline. Sure as it rains here in February I get vapor-lock whenever I fill up with PetroCan, run 'round all day and it's clear & sunny.

Anyone have handy solutions? Does a modern lead substitute/additive help?
 
Good thought TR3driver, likewise Percy. My spit does have a pretty keen heat shield, asbestos between two metal shields. That darned cat/can gets pretty hot!! Was also thinking of re-routing my gas line, and re-locating the filter, as well as looking for a more insulated line.

Anyone think that further improvement can be made if I replace the manifold and cat/can with headers?
 
Dudly said:
Anyone think that further improvement can be made if I replace the manifold and cat/can with headers?
Click to expand...
Kinda depends on what the exact problem is. If the fuel is boiling in the float bowl and/or jet; then anything that puts less heat into the carb will help. A working cat gets even hotter than the exhaust would be otherwise; and cast iron manifolds hold more heat than tubular ones do; so both changes should help IF the problem is fuel boiling inside the carb. Which, strictly speaking, isn't "vapor lock".

True vapor lock is when the fuel boils before it gets to the pump, leaving the pump full of vapor (which it can't pump well enough to pull liquid fuel through). If that is the problem, then you need to keep the line from the tank to the pump cooler. Or just pressurize it with an electric pump near the tank.
 
Good point Randall. I was speculating that perhaps another part of the puzzle may be the colder gas that I pumped created some sort of negative vacuum. The other part may be that the filter is right next to the carb, but is not directly protected by the heat shield. The filter is metal and perhaps acting as a “mini boiler”. This is why I thought re-locating the filter may help too.

Anyway, I really do appreciate all the help I get here. In June I will have owned her for a year. I’m sure much of my success in keeping her on the road can be split into thirds, Scott at Team Triumph, My nutty Canadian brother, and all you helpful nutz here on the BCF.

Thanks
 
Not technically a Canadian yet...
 
I am running with the ARE heat shield yet with stock exhaust. Still subject to fuel issues on hot day, after sitting for 15-30 minutes. However "vapor lock" like condition is much less frequent than without the shield installed.

I can definitely recommend the shield. It's a very nice product overall. On the TR6 it mounts between the carb face and the air filter. Easy install to say the least.
 
On my TR3, it sits between the carbs and the manifold, and fairly effectively blocks any access to anything beneath, like the starter and the alternator. I had to remove it to get those bits out when I was questioning their serviceability. I didn't put it back when I reinstalled those parts. I can always do it later, when I'm more confident it won't need to come right back out.

On hot days, I have had a little sputtering with hot starts, but it settles down in 10 seconds, or so. We've only had a couple of 85 - 90* F days.
 
Elliot,

Next time it happens (if it happens again), try looking at the fuel filter.

I had this happen to me in my '76 TR6 up until recently, and noted after I stopped the car once (and immediately went to the engine bay) that all of the fuel was draining out of the fuel filter back into the tank. Opening up the fuel filler cap, the fuel ran back into the filter again!

I am fairly sure the vent line is blocked, causing a vacuum to form in the tank... Perhaps this happened to you?
 
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