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Vapor lock. Heat shield for fuel pump?


Jedi Warrior
Another attempt at the vapor lock problem in the 1500 Midget:

I've got some heat sheath for the fuel lines. If nothing else, it will look better that the existing plumbers foam pipe stuff.

Also, got some insulating tape that I plan on putting on the back of the carb heat shield, around the carb fuel bowl (HS4 carb) and also around the mechanical fuel pump. I was going to insulate the back-up, under-the-hood, electric fuel pump but have read that, because it generates it's own heat, it would only serve to cook it even more.

While I'm at it, I was also thinking of making a heat shield for the mechanical fuel pump. If so, to maintain the same distance from the engine block, I was going to dispense with the gasket and just use some Ultra Black .

Comments welcome before I get cracking!



Good luck Adrian. I know you've been chasing this one for a long time.

If the heat shielding doesn't work... you still could consider mounting that electric pump at the back, below the fuel tank.


Jedi Warrior
Hey Doug!

How is it going?

Yeah, at least the problem is predictable. Park the car, come back and you be going max 10 mph for a mile or so before it clears.

I'm also thinking of mounting a PC fan to help with the ventilation but suspect I'll only be blowing the hot air around.

Next up is some bonnet louvres - my metal working equipment amounts to a vice, hack-saw, Dremel and file so you can imagine how that will turn out. However, getting rear-ended would look worse, I'm thinking.

Anyways, hope you are doing OK and enjoying the warm weather.



Jedi Hopeful
I had this problem up in Oregon on the 95+ days, but so far in San Antonio (TX) I'm OK in much hotter temps.

What I did was buy some heat shield tape (https://www.amazon.com/Heatshield-Reflect-Tape-1-1-Roll/dp/B002UPLB7E) and wrap it around the fuel filter, which was in-line just before the carbs. I also replaced the short section of fuel line that went between the metal fuel lines coming from under the car and the fuel filter. I used fuel line wrapped in metal mesh.

The Midget by the way has the pump back in the back.

I also by the way had considered the PC fan idea. In fact you can buy some nice little fan controllers for PCs that combine with temperature sensors. It would be a good bit of research to attach a series of temperature sensors to different locations, and see just where the heat is (or isn't) under actual driving conditions. Also it would let you move the fan around and see if it's actually having an effect.

An example of this kind of PC hardware is https://www.scythe-usa.com/product/acc/045/km02_detail.html

It would let you monitor 4 temperatures as well as the speeds of 4 fans if you want. It would be an interesting way to measure and test your temperature efforts without just making educated guesses.


Jedi Warrior

Many thanks for the link about monitoring the temperature around the PC fans. Very interesting.

I see you have a 1974 Midget - that is still a 1275 right? I had one (still do, but rusting away) for 10 years that had zero, zero, zero heat-related problems, and it gets stinking hot here in NC. So that is now puzzling me - I thought the heat problems were solely the misfortune of the 1500 engines.

In any event, I'm beginining to think, in my case, the only way is to somehow get the heat out of the engine bay - hence the louvre plan.



Jedi Hopeful
I'm not sure about the heat thing and my '74 1275. I had it in Oregon for a long time, and it seemed like any time we hit a 95+ day I'd have problems on rides over 5-10 miles. But now I've got it down in San Antonio TX and we're getting plenty of hot days, and I've done some pretty long drives now with the tape on the fuel filter and no problems. It struck me as the least insulated spot in the fuel "chain" as it were, beyond the carbs themselves.

My symptoms by the way were basically having it starved for gas (intermittent running) plus gas spluttering out of the front carb fuel float chamber. I put a piece of fuel hose on it to at least take the fuel down to the ground rather than over the manifold. I'm sure there used to be something there to do that in the past, but not anymore.
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