wndsofchng06

1954 century sedan. GA to NC

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I've noticed with the warmer weather she takes longer to start after sitting for more than a day,  almost like the fuel pump had to reprime. Anyone using a check valve? 

 

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It may be a case of carb bowl evaporation, especially if you are still forced to use Ethanol laced fuel.  Try this for a quick test.  Let it sit for a half hour with the hood open ( outdoors)  after your next run.  Then restart and put it away before it heats up again.  Then see if it will start quicker in the AM.

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The fuel pump is a check valve, it cannot drain back as far as I can tell. You could try a check valve at the back of the carb, but if the float bowls are drained then it will still have to fill regardless. Next time you let it sit, before starting pull one of the sight plugs on the side of the carburetor off and check fuel level. If empty or low, keep a small turkey baster of fuel and squeeze it through the bowl vent hole to fill the bowls, or squirt some into the engine to get it running. I usually just let it crank the extra 10-20 seconds to re prime itself if my car has been sitting, but I usually never let it sit more than a day if I can help it. 

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If you let a car sit, the fuel bowl will be empty. It could also be empty if the car was shut off hot. As much as I would love to get rid of Ethanol, and there are plenty of problems that can be attributed to it, I don't think this is one of them. In the 80s, one could expect gas to be cut with up to 10% of a mixture of Ethanol, Methanol, and MTBE as octane booster. You could expect the full 10% in super unleaded, regular a bit less. Both Methanol and MTBE boil at an even lower temperature than Ethanol. Some cars did have trouble, but widespread complaints about the gasoline in old cars just didn't exist then.

 

As Beemon said, the fuel pump is a check valve. Actually, it is two check valves. For the fuel to drain all the way back to the tank by gravity/siphon, both of them would need to leak, or there would need to be a pinhole in the fuel line from the tank breaking the seal.

 

Old time wisdom says that a car that drains the gas all the way back to the tank has a bad "foot valve" in the pump. This is the valve facing the gas tank. While it could be true if the gas were boiling in the pump at every shutdown, it probably isn't. Cars with this problem seem to do it in the dead of winter, too. More likely both valves leak (or there is a hole in the line).

 

Cars with leaking valves in the fuel pump will often start right up with a squirt of gas in the carb, but run the battery low or dead before the pump can suck the gas all the way up to the carb otherwise. Pump efficiency is terrible with leaking valves. Some extra crankshaft speed helps a lot.

 

Old time wisdom also says you should never mess around with a working valve. Today you would have to replace them for sure if they have an elastomer (rubber) valve, due to Ethanol in the fuel. Rubber ones probably seal ok right out of the box. If the valve is a bakelite disc, a new one will have to break in. You could try to lap it, but that often doesn't go well. One way or another those valves should seal before the pump goes back together. They should pull vacuum and hold it for a little while. Both of them. If they can pull and hold a good vaccum, the fuel is going to come up right away, and it won't matter much how fast the crank is turning.

 

New bakelite valves probably broke in ok in most cases when the car was in daily use. Mrs Jones probably wasn't going to let the car sit around a lot before putting some miles on it. Today, I wonder if any of them ever break in. I also wonder how many 12 volt conversions are done, and how many electric fuel pumps are installed just because these little valves aren't sealing, and no one realizes it.

Edited by Bloo (see edit history)
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20 hours ago, wndsofchng06 said:

I've noticed with the warmer weather she takes longer to start after sitting for more than a day,  almost like the fuel pump had to reprime. Anyone using a check valve? 

 

I do not experience this with my Carter on my 264.  You have a Carter carb?   I do not much go with the evaporation idea for this model as the original air cleaner is enclosed (no snorkel) and the vapor would have to make its way past the oil bath as well.  My thoughts that there would be a heck of a lot of vapor in the oil bath housing.  Are you running the original oil bath set up?    However, if my 264 sits for about a week it does take some cranking to start. Does not matter the weather.     The 401 on the 60 I could visibly watch the gas flow back through the filter to the pump. It is a new pump!    If  I run it every day there is no problem. Leave for a week and there is some cranking required.   I'm believing there is some drain back exacerbated with the heat of the engine(being a bit hotter due to the hot summer climate).   You can always try a one way valve and see what happens.       

Edited by avgwarhawk (see edit history)

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