04-19-2015, 05:44 PM | #21 | ||
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Re: Vapor Lock
Quote:
Quote:
Best true test for vapor lock: Keep a gallon of water with you. When the engine dies open the hood and pour a quart or two slowly on the mechanical fuel pump. Then, get back in and start it up. If it starts, you know it was vapor lock. I hung in there for total authenticity not wanting to put in an electric pump but I got tired of the engine dying (way too often at very inopportune moments) and having to get out, open the hood, and pour water on the mechanical pump to get it going again. So, I bit the bullet and put in the electric pump.
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04-19-2015, 05:59 PM | #22 |
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Re: Vapor Lock
I chased what I thought was vapor lock on my '51 for a couple of years. Even went so far as to install an electric pump. I finally found out it was a slight leak at the rim of the sediment bowl. I evened it out with wet-or-dry on my surface plate, installed a new gasket, and the leak was fixed. (I removed the electric pump a few years later, and have not needed it since). Surprisingly, cork bowl gaskets seem to work better and last longer than neoprene ones; I have no idea why.
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04-19-2015, 06:27 PM | #23 |
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Re: Vapor Lock
ladies & gents here is the answer to your dreaded vapor Lock. This is the Davis Rods Vapor Lock Eliminator kit & is available for one easy installment of $19.95 + S&H. What you get is 8 clothes pins made from the finest Brazilian hardwood & instructions on how to attach them to your fuel line.
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04-19-2015, 06:36 PM | #24 |
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Re: Vapor Lock
Henry put the fuel pump in the worst possible location. Besides being at the top rear against the firewall with no air circulation, he opened a direct channel from the valve chamber to the fuel pump diaphram to insure it received all the heat it needed to produce vapor lock. Insulating gaskets and phenolic spacers be damned, that direct passageway for heat is still there.
For those who, as our Old Henry was, not thrilled about installing a modern electric fuel pump to combat the problem, there is a viable solution that could easily have been done by anyone at any time back in the day: (G.M. has done some homework to confirm that this works.) I remember one old timer who said he used an original hydrostatic gage siamese fuel line to make this very modification. Providing a small return line from pump to tank will effectively keep the fuel flowing cool so as to not flash to vapor. This has been shown to work while the engine is running, but sadly, it's still a problem when you shut down unless you open the hood. Something to be said for Hot Rodders with no hoods!
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04-19-2015, 07:00 PM | #25 |
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Re: Vapor Lock
Funny thing about hoods; when I was having my problems, I got into the habit of leaving the hood up when parking it on hot days. I got a lot of funny looks (stock 8BA), but it always started.
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04-19-2015, 07:15 PM | #26 |
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Re: Vapor Lock
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04-19-2015, 07:20 PM | #27 |
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Re: Vapor Lock
In the case of Tubman a vacuum check back at the tank out let would tell you if you have leak down . he also shows that you can mistake other faults for VL .
when you park the car in the sun, turn the engine off, and run into the store to grab something. All of that cooling goes out the window (or up the chimney in this case) and the heat of the engine, regardless Henry one would assume the carb had completely dried out .during that short visit to the shop ?? a half a bowl of fuel will start the car regardless of the pump. Last edited by FlatheadTed; 04-19-2015 at 07:36 PM. |
04-19-2015, 07:48 PM | #28 | |
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Re: Vapor Lock
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Stuck in the no parking zone with vapor lock: Not a happy camper!
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04-19-2015, 08:19 PM | #29 |
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Re: Vapor Lock
sounds like you were in a mess of problems there Henry .
Something to try .A vacuum gage can be placed on the rear end of the fuel line ,air tight ,then the motor started ,when the vacuum reaches maximum shut the motor of, it should hold vacuum for at least 2 min this test can be done at the pump flex line or If the fuel line has been cut along its length any were then I suggest at the rear is best .Ted |
04-19-2015, 10:36 PM | #30 |
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Re: Vapor Lock
I could fill the screen with funny stories of my vapor lock before coming to understand it and deal with it. I probably had more than most because of where I live and drive. I live at 5,000 feet and regularly drive up to 10,000 feet and more. Higher altitude = lower air pressure = lower boiling temperature of everything including gasoline = more vapor lock.
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04-19-2015, 11:19 PM | #31 |
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Re: Vapor Lock
How about a discussion of the actual mechanics of Vapor Lock? I'll start and let's see where this goes? Off the top of my head from real world experience, without benefit (?) of scientific testing:
Heat begins the vaporization of fuel in the pump chamber> Vaporization raises the pump chamber pressure> Higher chamber pressure approximates the diaphragm spring pressure> Shorter diaphram stroke drastically reduces liquid fuel flow to carb> Vapor overloads the only relief of same at the carb's needle valve> Carb begins to starve, engine bucks> Without liquid fuel, pump gets uber hot, engine dies for lack of fuel> With the hood open, pump cools in 15 minutes> Do it all over again. Does anyone have an alternate explanation?
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04-20-2015, 01:20 PM | #32 |
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Re: Vapor Lock
[QUOTE=ford38v8;1072134]How about a discussion of the actual mechanics of Vapor Lock? I'll start and let's see where this goes? Off the top of my head from real world experience, without benefit (?) of scientific testing:
Heat begins the vaporization of fuel in the pump chamber> Vaporization raises the pump chamber pressure> Higher chamber pressure approximates the diaphragm spring pressure> Shorter diaphram stroke drastically reduces liquid fuel flow to carb> Vapor overloads the only relief of same at the carb's needle valve> Carb begins to starve, engine bucks> Without liquid fuel, pump gets uber hot, engine dies for lack of fuel> With the hood open, pump cools in 15 minutes> Do it all over again. I see lower fuel pressures right after the pump when the vapor lock starts, down in the 1 1/2lb range. G.M. ]
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04-20-2015, 02:01 PM | #33 |
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Re: Vapor Lock
And, that sounds understandable, George. As you realize, you can have positive PRESSURE with a vapor, or with an in-compressible liquid. In the case where the liquid turns to vapor (because of too much heat), the VAPOR pressure does nothing to move liquid fuel toward the carburetor. Almost like breathing IN TO, and OUT OF a balloon....no work is accomplished. DD
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04-20-2015, 03:13 PM | #34 |
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Re: Vapor Lock
maybe Someone should post here a accurate scale of what temperature each fuel company's fuel will turn to vapour ,this possibly could be got from there web sites . I would say its a lot higher than what you think it is .Ted
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04-20-2015, 03:25 PM | #35 |
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Re: Vapor Lock
Call & raise.
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04-20-2015, 03:51 PM | #36 |
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Re: Vapor Lock
Seems like I remember G.M. doing some testing and finding the boiling point (of the fuel) at just under 130 F. DD
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04-20-2015, 04:26 PM | #37 |
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Re: Vapor Lock
I'd sooner trust G.M.'s data than any you'd find from a fuel company website.
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04-20-2015, 05:02 PM | #38 |
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Re: Vapor Lock
The average flathead runs at 160 to 180 at 130 F why are the cars running at all ??
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04-20-2015, 05:04 PM | #39 | |
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Re: Vapor Lock
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04-20-2015, 05:11 PM | #40 | |
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Re: Vapor Lock
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But that boiling temperature would be much lower at my elevation and would be different for other gasolines and on other days. So, impossible to predict precisely.
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