fuel tank

Hi Lads/Lassies I'm having problems with the fuel supply on a tractor I am building i.e.as with most tractors the fuel tank sits higher than the carb and it floods the engine as you would expect. I recall reading somewhere about someone using a chicken drinker type feed to solve this problem, can anyone be of any help or maybe have some other solution.

Farmer Dave

Not being a country boy I don't know about chicken feeders but I have made a few Lunkenheimer style carbs. These have a very lightly sprung valve which covers the fuel inlet to the carb, as air is drawn through the carb on the induction cycle this lifts the valve and allows fuel to be drawn in. As the engine stops sucking in the fuel air mix the valve drops back down and shuts off the fuel supply to the carb.

These carbs were typically used on hit & miss engines particularly those from the US.

This shows the valve and its small spring

And this the hole that it covers

J

As the tractor has a high tank a carburretter having a float chamber with a float to control the fuel level ,should be used,

Most hit and miss farm engines had a tank lower than the carb and had a non return valve on the fuel pipe,

We have a chicken feeder, sold on ebay but never collected, so i may be able to help.

I can see how it would replace a float chamber, but have a similar effect.

The principal is the same as filling a glass with water, putting a saucer over it and turning it upside down. Some water flows into the saucer, but once past the rim, the water level stabilises keeping most of the water in the glass.

If a chicken or evaporation remove some water, a little dribbles into the saucer and a bit of air enters the glass, and the water level remains the same in the saucer.

I imagine a similar arrangement can be used of a pipe from a fuel tank into a fuel reservoir open to the air. Only enough fuel will leave the pipe to cover its end. The tank must NOT have a breather!

This arrangement would give a constant head but could be a bit less reliable in any environment where the fuel reservoir got shaken up.

Neil

What sort of scale is the tractor and what is the head difference between tank and carb. When the tank is full on my gallaway the level is about 5" above the Lunk' with no sign of flooding.

Its the spring that makes the difference, you can run the Lunk without a spring on an engine with a low tank as it just acts like a ball or flap non return valve with the weight of the valve being enough to close things off and stop the fuel draining back during the miss cycles. But when using with a high tank provided the spring pressure is just enough to counter the head pressure from the fuel it will shut off the flow.

J

Edited By JasonB on 15/05/2014 20:26:45

Thank you for your help lads ,I;m thinking I might try a lightly sprung valve in the fuel line, it would be similar to the valve you suggested Jason. Neil, I was wondering if it could be done with pipe work & air vents to avoid the open tank.

thanks again Farmer Dave

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Many motorbikes have a similar arrangement at the tanks are higher than the carbs.

They often work of the vacuum principle to open when the engine is running and closes when the engine is off. This vacuum is normally taken from the inlet manifold via a pipe to the petrol valve/tap.

e,g. **LINK**

Nick

Edited By Nick_G on 15/05/2014 23:30:47

Nick that looks a bit like it used a diaphram which is very similar to the demand regulators that are used when you want to run IC engines on gas rather than fuel. See the third item on this page

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Yes Jason very similar. These are usually about 1" - 1 1/4" in size.

I had to take one to pieces once to replace the diaphram. Quite tricky as the diaphram is very, very thin and quite small. I ended up holding it in position with grease in the end while I reassembled the rascal and relied on the petrol flowing through it to dissolve the grease.

Nick