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| carburator seems to dry out https://slantsix.org/forum/viewtopic.php?t=41591 |
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| Author: | thedeputy [ Tue Aug 24, 2010 4:28 am ] |
| Post subject: | carburator seems to dry out |
When I want to start my valiant, after it's been standing for a couple or days, it takes a pretty long time of cranking before it fires up. if I shut it down when I finally got it going, she fires up immediately. It seems as though the bowl of the carb is drying up or something, losing all the fuel. It's a carter bbd of unknown origin on a factory super-six intake. I allready renewed the fuel pump. What path do I need to follow to fix this? Antoon |
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| Author: | 66aCUDA [ Tue Aug 24, 2010 6:07 am ] |
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Antoon I have the same issue with a couple of BBDs on my trucks. One of them is a NOS carb the other an older one. Frank |
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| Author: | olafla [ Tue Aug 24, 2010 6:29 am ] |
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Hi guys. The reason for you problem is that the intake and exhaust manifols are bolted together. That gives the necessary heat to prevent carburetor icing, but it also distributes the heat up to your carburetor when you turn off your engine, and the fuel evaporates. Modern fuels actually have added oxygen into it in the production process to reduce emissions, and that makes the fuel even more volatile. The solution is to replace the fuel line and install a heat shield between the carb and maniold. This is a theme you can find a lot of info about, see the FAQ in the engine section about Fuel Line Mod, and make a search for 'heat shield'. Also look at Aggressive Ted's solution at his homepage here. Olaf |
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| Author: | Brussell [ Tue Aug 24, 2010 6:29 am ] |
| Post subject: | |
Hey, I've been getting the exact same problem. Couple things I'm thinking it could be. The fuel line leads up to the carb, perhaps fuel is draining backwards. There is a very small drip leak (one drip for say 40L of fuel) where the fuel line bolts into the carb, I'm not sure if this is because the fuel pump itself is broken, or whether the fuel pump allows fuel to travel both ways. Might be something wrong with the carb meaning fuel can evaporate. I think a way to check it would be to block the fuel line somewhere, say squeeze the line just after the filter. to stop fuel moving. that way you can see if fuel is back tracking or if it's coming out of your carb. Also check the fuel filter mod in the sticky section it's worthwhile. |
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| Author: | thedeputy [ Tue Aug 24, 2010 8:03 am ] |
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@olafla, My problem is only occuring after some days. What you're describing would mean that it won't start even after sitting a few hours. That's not the case, one, or two days is also not a problem. I just give it two taps at the acceleratorpedal, and she fires right up. Would a carb rebuilt, with new gaskets provide a solution? Antoon |
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| Author: | olafla [ Tue Aug 24, 2010 9:31 am ] |
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I have the same problems myself in my Aspen, difficult starting after some days. I have made a heat shield and will install that and new fuel lines together with my new carburetor as soon as I get hold of a new air cleaner, and will post pics and report back on the difference. In the meantime, take a look the other threads a few lines up or down in the engine section, and also see these threads: Super rich hot soak starting Hard starting after engine is hot then warm Starting problems So, you can see it is not a new problem, and the solution is known. Olaf. |
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| Author: | Aggressive Ted [ Tue Aug 24, 2010 9:50 am ] |
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If your sure it's not do to heat soak, it sounds like you need a new needle and seat to stop the fuel from bleeding off. I have a pressure gauge on mine and it always reads between 4 and 9 pounds, cold or hot. |
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| Author: | olafla [ Tue Aug 24, 2010 10:14 am ] |
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I agree on new needle and seat to stop a leak in any case, but shouldn't there always be enogh fuel below the fuel intake level to start the engine, even with a small leak? I have a BBD and don't know the 1-barrels in detail. Olaf. |
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| Author: | thedeputy [ Tue Aug 24, 2010 11:20 am ] |
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Where can I get a new needle and seat? Oh and by the way it's a 2-barrel carb. Thanks, Antoon |
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| Author: | Josh P [ Tue Aug 24, 2010 12:05 pm ] |
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Most rebuild kits have them. |
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| Author: | carlherrnstein [ Tue Aug 24, 2010 1:09 pm ] |
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My truck does a similar thing, after a week or so of sitting it has to be cranked over a lot to start it. I just figured the fuel was evaporating out of the carburetor. I don't think that there is anything awry with your engine. |
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| Author: | emsvitil [ Tue Aug 24, 2010 1:24 pm ] |
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I added an inline electric pump at the gas tank. Run it for about 30 seconds before starting to fill up the carb. Make sure the electric pump will let the gas flow thru it when it's off. I used one of those cheap vibrating ones that look like a cube. |
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| Author: | Doc [ Tue Aug 24, 2010 2:21 pm ] |
| Post subject: | |
Yes, a carburator will "dry-out" after sitting a few days. I have a small, "flip top" plastic, squeeze bottle I keep filled with gas, when I go to start a car that has been sitting, I pop the hood and squirt some fuel into the carb... and the engine fires right-up with the first turn of the key. DD |
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| Author: | olafla [ Tue Aug 24, 2010 4:57 pm ] |
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Doc, do you know why it dries out, and is it the same for different carburetors used on slant sixes? I know there are different bowl vent systems, and my BBD has no bowl vent at all. Olaf. |
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| Author: | Doc [ Tue Aug 24, 2010 5:13 pm ] |
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I feel that it has a lot to do with heat soak (the fuel can boil inside the carb after hot shut-off) and venting. (the vapors have to go somewhere) Insulating the carb from the heat helps, adding a vapor return line & closing the float bowl vents to the open air, also helps. And then there is the "clean burning" fuel we have... that gas fomulation seems to evaporate quickly. Face it... we have an open "cup-of-gas" sitting on top of a hot engine... that is not a good situation and it is a major reason why newer cars use EFI. DD |
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