23 Roadster Fuel Line

[tommyleea]

More about the fuel delivery than the line itself. I understand my 8N tractor, with gravity feed, and the fuel tank above the carb. However, at least on my T, if I run a line from the tank to the carb, the angle is downward, or at least level, which is a good thing. Going from the tank to the engine mount wood block opening for the line is still a downward angle. But, from the wood block opening at the frame to the carb inlet is uphill. Seems like it should be downhill all the way. What makes the fuel continue into the carb during the uphill portion? I have a new fuel line, so before I bend it......Thanks...Tommy

[Norman Kling]

The most important thing about the route of the fuel line is, the line should slope up at each end with one low point between the two ends. Do not have a high point somewhere between the two ends because an air or vapor bubble can form and rise to that point then the fuel will stop flowing. It will just compress the air. This is called,"vapor lock". I will attach pictures of the way I ran mine.It goes straight across over the exhaust pipe, lowest point at clamp which is attached to the bracket at the brake cross shaft and up toward the carburetor.

[tommyleea]

The most important thing about the route of the fuel line is, the line should slope up at each end with one low point between the two ends. Do not have a high point somewhere between the two ends because an air or vapor bubble can form and rise to that point then the fuel will stop flowing. It will just compress the air. This is called,"vapor lock". I will attach pictures of the way I ran mine.It goes straight across over the exhaust pipe, lowest point at clamp which is attached to the bracket at the brake cross shaft and up toward the carburetor. at sediment bulb.jpg

Thanks Norman. I guess I still don't understand how the fuel runs uphill, without a pump. Must be a scavenge thing. Tommy

[Steve Jelf]

The gas "runs uphill" to the carburetor because it's pushed by the higher level of fuel behind it. Theoretically you could run the line clear down to the floor, and the greater weight caused by the higher level at the tank end would still push gas up to the carb. A liquid seeks its own level whether it's water flowing down a stream, or gas in a fuel line. You can see this with a clear plastic tube with both ends at the same level and the middle down low. Pour a liquid into one end and watch it rise in the other end to the same level. It's like the water in your house. Your pipes run up from the ground into the house, but the greater weight of the water in the tower pushes the water up to your faucets.

[Allan]

If you think back to the old water bags that used to hang at railway stations, the hose was hung up at the top. To get your cupful, you had to lower the side hose until the end was below the level of the water in the bag. Then it would flow. As long as the the pourer end was above the water level the contents were safe.
As long as the bottom of the fuel tank is above the carburetor inlet, the fuel will always flow.

Allan from down under.

[tommyleea]

Thanks Steve and Allan..