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HighAltitudeTR3
Jedi Trainee
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Yeah, it’s an itch I’ve been meaning to scratch.
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TR2/3/3A Doesn’t want to start up again after a ride...
- Thread starter HighAltitudeTR3
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Yes it does sound more and more like boiling fuel especially if you hear it. But yeah a new dizzy will make difference when things cool off, like better start up (with a good strong coil) and response plus I found that my idle and throttle responded better when I put a new distributor on.
Back in auto shop in the 1968 the auto shop teacher was one of these guys who said vapor lock did not exist (probably because we lived in Washington State). Anyways back then people would put clothes pins on their fuel lines and these little copper kinda deals in the fuel line to stop this questionable vapor lock. The shop teacher would maintain the problem was that the car had inferior fuel and something wrong with the ignition or the motor had poor compression. He also would say that the car starts on fumes or an unmeasurable amount of gas so it did not need raw fuel. But I honestly do not know, and I respect John and Randal and others who say vapor lock is real.
Back in auto shop in the 1968 the auto shop teacher was one of these guys who said vapor lock did not exist (probably because we lived in Washington State). Anyways back then people would put clothes pins on their fuel lines and these little copper kinda deals in the fuel line to stop this questionable vapor lock. The shop teacher would maintain the problem was that the car had inferior fuel and something wrong with the ignition or the motor had poor compression. He also would say that the car starts on fumes or an unmeasurable amount of gas so it did not need raw fuel. But I honestly do not know, and I respect John and Randal and others who say vapor lock is real.
CJD
Yoda
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It's real. One May a few years ago we were already in the "above 100 degrees" range here in TX. I had a 50% scale RC plane (yep, no misprint...half the size of a real plane) which I could not get to run. It would start, chug and die. I hand propped this 28" propeller for 8 straight hours trying to figure out what was going on. Finally, exhausted and beaten...I grabbed a drink and sat down to gawk at this huge contraption that would not run. The fuel lines on these large planes are clear. As I sat there brooding, I happened to catch a glimps of the fuel line to the carbs.
A tiny bubble would form, about like in a soda glass. As I watched, the bubble grew, and grew, until it blew all the fuel out of the line!! Mind you, it was not draining back to the tank...it was flat vaporizing.
I came to the conclusion that the gas companies weren't mixing fuel for 100 degrees in May. Sure enough...change and gas and the plane ran without a single issue.
A tiny bubble would form, about like in a soda glass. As I watched, the bubble grew, and grew, until it blew all the fuel out of the line!! Mind you, it was not draining back to the tank...it was flat vaporizing.
I came to the conclusion that the gas companies weren't mixing fuel for 100 degrees in May. Sure enough...change and gas and the plane ran without a single issue.
charleyf
Luke Skywalker
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As I understand what happened, vapor lock is what killed the MGA twin cam motor. Apparently the fuel in the rear carb got so hot that it vaporized before much of it could get to the motor . This is after the engine got warmed up / hot. It apparently took a while to figure out the problem and by then they had given up on the motor. There was to much heat below the rear carb/ float bowl. So it does not only happen after one turns off the motor but during the running. Of course what also happened in this case was that it leaned the rear two cylinders out to the point of trashing the motor.
mt10flyer
Senior Member
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The problem is definitely vapor lock. I live at 6000' and both my Series IIa Land Rover and the TR3 have had this problem. The mechanical fuel pump is of course located on the hot engine block. Upon shut down the fuel will vaporize in the line, especially the one going UP to the carbs (the fuel vapor likes to go up). I relocated the fuel lines away from the block as far as possible and on the TR3 that worked. If it happens and you find yourself without starter fluid, priming with the lever at the fuel pump will work BTW.
The Land Rover was more difficult. It suffered from the same fuel pump situation but the added bonus is that the down-draft carb sits on top of the manifolds which are super hot. Upon shut-down the fuel in the bowl immediately vaporizes along with the fuel line. I was forced to add an electric fuel pump (and bypass the mechanical one completely) which supplies the fuel at a slightly higher pressure. I switch on the ignition for a moment and let the fuel pump run which forces the vapor through the carb and out before engaging the starter. Problem gone.
The Land Rover was more difficult. It suffered from the same fuel pump situation but the added bonus is that the down-draft carb sits on top of the manifolds which are super hot. Upon shut-down the fuel in the bowl immediately vaporizes along with the fuel line. I was forced to add an electric fuel pump (and bypass the mechanical one completely) which supplies the fuel at a slightly higher pressure. I switch on the ignition for a moment and let the fuel pump run which forces the vapor through the carb and out before engaging the starter. Problem gone.