| Dustbowl | -- 10-23-2018 @ 5:07 PM |
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If my 36 Ford sits more than a week, it takes about 20-30 seconds of cranking before it starts. If less than a week, it starts immediately. I assume that in the week, the carb (standard 97) bowl dries out as gasoline evaporates. So I have to crank a long time for the fuel pump to fill the bow. Is my assumption of the problem cause correct and, if so, what can I do to eliminate or reduce the problem?
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| Drbrown | -- 10-23-2018 @ 7:51 PM |
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If your carb doesn't leak internally or externally, then (some) gas is probably seeping back to the tank. I'm not knowledgeable but some stock mechanical pumps have valves in them to prevent back-flow to the tank. I believe one can also buy a back-flow presenter valve. In addition to its stock mechanical pump, and like some members at this forum, my '47 has an Airtex electric pump at the tank which I turn on for about 10 seconds before starting the engine. And its also available if the mechanical pump fails or the engine experiences vapor lock.
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| ken ct. | -- 10-23-2018 @ 9:54 PM |
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It shouldn't evaporate in a week. Try another Power Valve , 97's use a # 65. I have some if you need one. I also can test them for leakage with a tool I have. ken ct
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| ford38v8 | -- 10-23-2018 @ 10:15 PM |
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Dustbowl, Ken may have hit on the cause of your losing fuel. Modern gasoline is not only more volatile than in bygone times, it is also destructive of diaphragms in fuel pumps and power valves. Drbrown, with all due respect, to my knowledge, all carburetors and all mechanical pumps have valves that prevent flow back to the tank. Therefore, adding an additional one way valve is additional redundancy. Alan
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| mfirth | -- 10-24-2018 @ 4:36 AM |
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Actually, todays fuel will evaporate quickly in a hot conditions. A marine mechanic i know put some in a jar & in an hour you could see the results of evaporation. I put an electric pump on my 52 Vic & use it to prime the carb or overcome vapor lock etc. Hope this helps, mike
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| ken ct. | -- 10-24-2018 @ 5:55 AM |
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Allen is right but Stromberg PV have NO rubber diaphragm in them. Simply a mechanical with an internal spring in it ,But they can still leak if they don't seat properly. Smell your dipstick for gas smell. ken ct
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| TomO | -- 10-24-2018 @ 9:07 AM |
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Drbrown, you usually post good information, but in the case of fuel draining back to the tank, it is almost impossible. The fuel inlet to the carburetor is above the fuel level, so there is an air gap in that the fuel cannot jump. The fuel pump sediment bowl fuel level may be high enough so that there is not an air gap, but once the fuel starts draining back to the tank, there will be an air gap. Mike, I have left a graduated cup, with 2 ounces of fuel in it, on my work bench for more than a week and very little evaporated. The summer grade fuel sold on the US is designed to have a low volatility to reduce air pollution and differs by state with the colder states allowing more volatility than the warmer states. A Ford fuel pump should prime in 18 seconds and fill the carburetor enough to start the engine in 30 seconds. If it does not, there is probably: an air leak in the supply line, the push rod is worn, the fuel pump is worn out or the line is plugged. Dustbowl's fuel pump is operating within specifications, so Ken's diagnosis of a leak in the carburetor is probably correct. Tom
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| JT Ford | -- 10-24-2018 @ 10:20 AM |
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If you grind on a starter for 30 seconds, it seams like for ever!
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| Drbrown | -- 10-24-2018 @ 6:32 PM |
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As said, I'm not as "knowledgeable" as you and many more experienced others here but I was remembering other posts re i.e leaking flex hoses at pump intake allowing air to enter the line when car sits and gas to drain back to tank, and/or when running allowing air to be sucked into pump etc etc.. And if it "sits for more than a week" ..... how much more ?
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| mfirth | -- 10-25-2018 @ 4:34 AM |
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Tom, thanks for the info. I'm in Ohio & every time i shut my 8ba with 180 stats,down the gas in the carb boils, expands & floods the engine. Have friends with various vehicles & they all experience the same thing. Boats using "marine fuel" do not. Isn't there a difference in formulations there too? Thanks 4 sharing your knowledge. m
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| TomO | -- 10-25-2018 @ 7:11 AM |
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Mike, There are many different blends of gasoline, and the blend that you get depends upon where you live and what the EPA says about the environment. All blends of fuel need to meet the driveablity criteria of not being just volatile enough to pass the EPA rules on evaporation and yet being volatile enough to become a vapor in the intake manifold. Your "boiling gas" is probably leaking past the power valve. In my area, we have "reformulated fuel" and it seems to leak past seals faster than the fuel used in rural areas that does not contain Ethanol. Temperature seems to have an effect on this. My Lincoln will flood on a hot day, when I stop the engine, unless I open the hood. I have not been able to find a good way to stop the fuel from leaking out of the bowl on that teapot yet. The Lincoln is much worse than a flathead for underhood temperatures. It gets so hot that you can burn your hand on the hood release. If you have a spare carburetor or store your car for the winter, have your carburetor rebuilt by Charlie Schwendler. ..cas5845@yahoo.com . He will machine the bowl so that there will be no vacuum leaks and the power valve will seat and not leak. Here is a link to an article on gasoline and its vapor pressure. https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf Tom
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| mfirth | -- 10-26-2018 @ 12:38 PM |
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Thanks Tom. My carb is a new Dennis Carpenter which i bought two years ago. The previous one leaked or whatever so i got the new one & there was no difference....... I know guys with all kinds of cars, big blocks, vw etc and they all do the same thing. One fellow has a 352 in an Edsel with a clear fuel filter & you can watch the fuel bubble in the filter when it is hot. It's weird ! I just put a shut off on the 52 Vic so i can run it dry when i put it in the garage. No more fumes. Yippee! Thanks again & have a GR8 weekend.
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| Dustbowl | -- 10-26-2018 @ 1:46 PM |
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I usually get good suggestions when I post a problem on this forum but, in this case, most of the responses are, in the current jargon, 'fake news". For example, as a former oil refinery engineer, I know that gasoline volatility specifications have not significantly changed in the past 50 years. And an open container of gasoline will mostly, if not entirely, evaporate in a week. The only really useful idea came from ken ct, who suggests changing the power valve. My question for ken is whether the power valve you suggest is any different than the one which is usually included in a carb rebuild kit? And if so, how can I get the one you suggest?
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| ken ct. | -- 10-26-2018 @ 2:08 PM |
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If you send me your old PV I will check it for leakage N/C if you pay shipping both ways. If bad I will contact you and see what you want to do. I have tested used ones for $10 if you want a good one back. It should say 65 stamped on it. ken Isidor ct. Shipping should be approx. $3 each way in a small padded envolope
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| ford38v8 | -- 10-26-2018 @ 2:21 PM |
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A polite seeker of wisdom will refrain from showing his a$$ by insulting those who offer help. Alan
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