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Posted

Hi,

I have had my 1940 LaSalle half way to forever, and vapor lock has always been a problem. Yesterday, during a 70 mile run in 70-degree weather, I caught it in the act when the Dear Lady said, "I'm done," for a while. Inspection showed that the fuel was visibly boiling in the fuel pump as could easily be seen in the glass bowl on the top of the pump. Engine temperature was on the cool side of normal. After 15 minutes of cool-down time, the car ran again--for a while. As I drove home, fuel again was an issue as the engine cut in and out intermittently.

In past years I bypassed the fuel pump and ran an insulated rubber fuel line to the carburetor, fed by an electric pump. That worked reasonably well other than on really hot summer days. Then last year I got all inspired, had Terrill rebuild the old mechanical pump, and hooked up the original fuel flow.

I am seeing that the fuel pump lies just a couple of inches from the driver's side exhaust manifold. There is no heat shield and no insulation between the pump and the manifold. No wonder the pump gets hot!

I guess my questions are, did Cadillac really make 10 or so years of engines that will not run after just a few miles due to overheated fuel pumps? Is there supposed to be a heat shield between the pump and the exhaust manifold?

And if so, what have other owners done to make their flat heads usuable? My LaSalle is, at the moment, no more useful than a yard decoration. :(

--Tom

Posted

-- did Cadillac really make 10 or so years of engines that will not run after just a few miles due to overheated fuel pumps?

When Cadillac made the fuel pump in question, it did not pump ethanol laced fuel through it. I doubt the car came with a heat shield from the factory. Adding one now though would not be a bad idea, unless originality is a major concern.

Posted

Which fuel pump do you have--original equipment with bowl on side or circa 1943 factory replacement with inverted bowl on top of the pump? The factory change during the era demonstrates that vapor lock was indeed a problem when your car was relatively new. 1946-48 Cad flatheads had the inverted-bowl-on-top pump, which is the best to use these days, given ethanol-laced fuels. The Cad-LaS Club magazine The Self-Starter has an article by John Washburn on these within the past three years or so. If you're a CLC member, suggest you contact Mr. Washburn for details.

I agree that fabricating a heat shield is a good solution. Or just wrap insulating material, such as starter wraps found at most retail auto parts chain stores, around the pump, using velcro fasteners so the insulation can be quickly removed for show.

Another solution (rather, this will **contribute** to a solution) is to remove the fuel line between pump and carb and wrap it with "Cool Tape," available at performance stores for about $20 in a blister pack. Do a spiral wrap with a 50% overlap, leaving an inch or so of fuel line unwrapped at each end. Then for a period appearance, slip some asphalted corrugated loom material (found at better electronics stores but not at Radio Shack) over the wrapped line to hide the Cool Tape. The fuel line is also subject to being heated by the exhaust manifolds' placement above the cylinder heads.

It's just a fact of life that we have to develop some work-arounds given the chemical changes in fuels and oils. The good news is that ingenious problem-solving collectors are doing so! BTW, none of these are my own original ideas, so I don't include myself in that category.

Good luck and please keep us posted.

Posted

Hi, and thank you for your input.

I have the fuel pump with the bowl on top. I will do as you suggested and wrap/insulate the fuel pump. I'll also make a heat shield to go between the manifold and the pump, and put insulating wrap on the manifold. The fuel line is already insulated.

It's been a while since I have put points in her, so I'll pull out the distributor, check the vacuum advance for proper function, and install points and a condenser. I have already replaced the coil, suspecting that high engine compartment heat was making it fail intermittently. I'll set the ignition timing to specs when I reinstall the distributor.

Next step will be a propane generator in the truck to run a portable air conditioner to keep cold air on that side of the engine! Or, as a more practical approach, I could put in a 3 or 4 inch duct to send outside air flow to splay over the fuel pump...

I'll post the results as soon as I have some more long distance experiences with the car.

--Tom

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