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Old 12-15-2014, 02:46 PM
The Arkansas Traveler The Arkansas Traveler is offline
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Default Vapor-lock ways to solve?

While changing my oil filter on my (new to me) '60 squarebird, I notice the fuel pump has no connected lines in or out. (Magic car?) From a letter to a garage, I knew that the previous owner in the Arkansas august heat of 1990,had had problems w/ it running hot and dying as though it was not getting gas. He would let it cool down a while and drive a bit, with the same result, especialy at stop signs.} They parked it, never to drive again until now. So I crawl under the back of the car and sure enough someone has added an electric fuel pump and wires, attached just out of the tank. "THE NEW TANK". My new Christmas present tank also arrived on my doorstep 20 minutes later. (stupid grin now) So I strongly suspect either someone was lazy and could drop in the electric inline pump and run some wires quicker than remove the OEM pump from behind the ac pump, OR ( a common way to try and fix vapor-lock) they tossed this on, in hopes of fixing what strongly sounds to me like vapor lock.
Question: Is vapor-lock a problem w/ the older t-birds? Have we came up w/ a proven way to fix the problem? I notice that there is no fuel return line to the tank. I know at one time they made a inline fuel filter w/ two outlets. One for the engine, the other for a fuel line returnto the tank. This continuious circulation can keep the fuel from reaching a boiling point under the heat of the hood and the engine just drawls off of the circultaion. If I keep the electric pump I would think the manual pump should be removed and a plate cover the hole, right? Anyone in the hot states have opinions and ideas? Custom work for a return would mean adding a line to the tank. Do I have a vapor-lock problem? Could I make this post any longer?
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Old 12-15-2014, 03:43 PM
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simplyconnected simplyconnected is offline
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You have two issues that require two answers:

Vapor lock only happens on the 'suction' side of a fuel line. That's the vacuum side with negative pressure. 'Pressure' is the operative here because gasoline boils at a MUCH lower temp when it is under a partial vacuum.

Loose connections can introduce air that looks just like vapor lock, so make sure all your connections are tightly sealed.

Since your new electric fuel pump is located at the tank, there isn't much chance of a suction leak. Your suction side is probably only a foot long, if that. Also, these lines are never in direct sunlight.

Carburetors are vented to atmosphere inside the float bowl. When the liquid level goes down, the needle opens until the bowl level raises again. Any air in the line simply goes past the needle valve, into the bowl and out the vent. Your pump has no problem drawing a vacuum on one side and pumping intermittent air, as long as the pump is wet. OEM pumps also include a check valve so they don't need a 'prime' after sitting for days.

Make sure your fuel tank is vented. Some tanks have a separate vent tube that snakes around my trunk (like my Galaxie) and others use a vented gas cap (like Squarebirds). Either way, the best fuel pumps cannot compete against a tightly sealed tank with either a vacuum (like on a long trip) or summertime heat which causes gasoline to expand and build pressure.

I have seen it first hand. I'm driving on the interstate for two hours and the gas gauge shows 1/4 full but the car starts bucking and dies. Open the gas cap (to add a gallon of gas) and a huge inrush of air goes in. Now the engine starts. Did the gauge lie? No. Did added gas help? Not really. A vented cap remedied the problem. It really is a system of components working together.

Usually when a car sits for years, the gas evaporates leaving varnish. When the new owner tries to start, all that crap starts floating down the fuel line. In extreme cases, the pickup tube inside the tank will be clogged, simulating the conditon of being out of gas or having vapor lock. Get a flashlight and look inside the tank. - Dave
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Old 12-15-2014, 04:42 PM
The Arkansas Traveler The Arkansas Traveler is offline
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Default vaporlock

At this point, I have yet to run the vehicle, so my vapor-lock problem is all theoretical. Should I stick to the OEM pump or keep the in-line electric? I was excited to see a new fuel tank for sure. I plan on emptying, dropping and flushing the tank, while inspectiong the sending unit. The cap was new as well. I'll look to see if it is vented. The new rubber is in good shape. The OEM metal line, I should replace.
I just had recieved my new tank, sending unit and rubber grommet. My next project will be dropping the pan and pump. Still cleaning on the oil side before I tackle fuel. Thanks for your input. I like the way you think.

PS:Hope they got your grandson stablized and comfortable.
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Old 12-15-2014, 06:45 PM
Joe Johnston Joe Johnston is offline
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I would retain the electric pump.
1-IF it is working, why spend money to replace something you don't really need to replace?
2-Its quite possible your current mechanical pump is old and not suitable for our ethanol additives
3-If you seldom drive your car (like me) the electric will quickly fill the carb fuel bowls and the car will start quickly with minimum cranking. My cars sit several weeks at a time and start right up.
4-Should you at some point replace the mechanical pump, the electric can still be retained as the electric will push gas through the mechanical to fill the carb bowls (however some electric pumps add a lot of resistance to fuel being pulled through by a mechanical on the engine. Just depends on the type of pump you have.)

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Old 12-15-2014, 07:42 PM
Tbird1044 Tbird1044 is offline
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There is a lot of personnal choice on this one.
I installed an electric pump at the tank and use it in series with the mechanical pump.
The electric pump gives me 2 options with a dual acting switch connected to the pump. Most times I use it for priming the carb if the car has been sitting for a while. If the mechanical pump ever fails on me on the road, I can quickly bypass the mechanical pump by installing a short piece of rubber tubing, and turn on the electric and continue to drive. This has saved me in the past and prevented a tow home.
Another thought is, do you still have the vacuum wiper motor? The fuel pumps were dual acting and used to create a vacuum to help the w/s wipers during low engine vacuum. This may be another consideration.

Last edited by Tbird1044 : 12-15-2014 at 07:45 PM. Reason: wrong word
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Old 12-15-2014, 09:03 PM
The Arkansas Traveler The Arkansas Traveler is offline
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Default My wipers may not be adequate at low speeds?

"do you still have the vacuum wiper motor? The fuel pumps were dual acting and used to create a vacuum to help the w/s wipers during low engine vacuum."
Question: So in this case if pump is on the block, but not pumping fluid, my wipers may not be adequate at slow speeds? Interesting. So I am sure there is an up-grade possible on wipers as well.
Good advice and points to consider from everyone. Thank you all. If I keep the electric, I'll clean up the wiring and add a block-off plate onto the block.
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Old 12-15-2014, 09:15 PM
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YellowRose YellowRose is offline
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Default Vapor-lock ways to solve?

In my opinion, those vacuum powered wipers were never any good anyway. So I replaced mine, as many others have, with an electric motor. The information on this is in the TRL. That is the way to go, and you can even add washers with it if you want to.

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Old 12-16-2014, 09:21 AM
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Dan Leavens Dan Leavens is offline
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Vacuum powered wipers are always a mystery and at the same time unique. When " under load " going up a rise ( hill ) in the highway they stutter / hesitate and then move again. Part of the mystique of these classics and their tiny wiper blades
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