DwightMann

When I fill my tank, I get fuel dripping from my spinner. I think that it may be following the crankshaft to the prop hub. I could be wrong. Any ideas what it may be or how to correct this?

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dmccormick001

That's going to be almost impossible for anyone to help you with on a forum like this without a lot more information. You're going to have to find the source of the leak first, and then you should be able to get some help and advice on what to do to fix the problem. We need a lot more info, like the model of the engine, whether it's mounted inverted or not, new or used, etc. Take the cowling and the spinner off so you can see what's happening, locate the source of the leak, (i.e. the front bearing, the pump or regulator, the carb, a fuel line, etc.) and then report back to us. It might help to use an old trick, take a small amount of fuel and add some dark food coloring to it so you can see where it comes from more easily.

David

42etus

My Feedback: (2)

Do you get the dripping before you even run the engine? What engine are you talking about here? What is the height of the fuel tank compared to the engine? The more info you can provide, the more likely you'll get the problem solved.
Paul

DwightMann

The engine is a F-120 mounted inverted (obviously an older engine). The tank is mounted approximately 12" back. When in flight it would be about level with the carb, but it is a taildragger, so it is probably at least 3" lower when on the ground being filled. The dripping happens before I start the engine, almost as soon as I start to fill the tank. It is not comming from the fill or pressure lines.

Jetdesign

My Feedback: (8)

Is it a two line system or a three line system? Is fuel dribbling out of the carb when you fill?

DwightMann

It is a 2 line system and yes fuel also drips from the carb. Where would I look to see if it is comming from the pump? or bearings? Is it necessary/ advisable to pinch the lines going to the engine when I fill?

petec

My Feedback: (58)

So it's a taildragger and you get fuel dripping from the spinner when fueling? Interesting that the fuel is running uphill. Take me through the the process you use when filling. The liquid is going to take the path of least resistence and a piece of fuel tubing should offer less than any path in the engine.

Jetdesign

My Feedback: (8)

Is this a 2 line system with a 'T' for filling? Are you sure your carb is fully closed when you fill? If not, fuel could be going to the carb when you fill and start dribbling out - I had a similar problem not so long ago, which was solved by holding down my throttle kill button while I turned off my plane.

DwightMann

It is a 2 line system. The line from the tank to the carb has a "T" fitting which leads to a line that I use to fill the plane and plug when flying. The line from the pump to the tank has a check valve, then a "T" with a line that is used as a vent when filling and plug when flying. I have the throttle fully closed when filling. The "T" used to vent is between the check valve and the tank, so the fuel should go through the vent and not the pump when flowing that direction. I will disassemble things and see if the check valve is functioning correctly

petec

My Feedback: (58)

That is the same way all my YS engines are plumbed. The trouble I am having picturing in my mind's eye is how you are getting fuel out around the spinner. Did you check the nipples right above the regulator?

A kink in the fuel line between the klunk and the tank come to mind but you would more than likely have other issues in that case like having to run the needle 2 or more turns open or erratic running at idle.

DwightMann

I disconnected the line from the pump at the engine. When I filled the tank, fuel came out of the line indicating that the check valve was not working properly. It is not in backwards, it is easy to blow air in the right direction.
I have only been able to get it to run 1 time and that was when it fired right up. The other times, it didn't fire up right away and after that it seemed to be flooded. Could a bad check valve be the source of my problems?

Jetdesign

My Feedback: (8)

So you're saying the check valve between the pump and the tank, which is the pressure line, is leaking?

YS engines use tank pressure to force fuel to the engine whenever you're over a high idle (high idle and below the engine will 'suck' fuel rather than 'push' it). If the check valve is not working properly, you will lose tank pressure and thus start to starve the system of fuel pressure.

I don't have enough experience to know how this would translate into fuel leaking when you fill, unless the pressure in the tank from the end of a flight is forcing fuel through your exhaust pressure line up to the pump?

I would definitely change that check valve. The last thing you need is a cheap, replaceable part causing you problems.

w8ye

My Feedback: (16)

What brand engine is this?

If this is a Y-S, a leak from the front of the crank shaft is not good. It means you need a new front seal and new bearings

DwightMann

The engine is a YS F-120. I think that the fuel was leaking from the fittings at the pump. I certainly hope that it is not from the bearing and seal. What is the easiest way to check the seal/ bearing?

w8ye

My Feedback: (16)

If the engine turns over real smoothly with no feel of friction or roughness, the bearings are probably OK.

The Y-S 120's were made for years with many models and I was not familiar with the F-120

I was wanting to make a point for casual readers looking at this thread that a Y-S engine must have a sealed crankcase and if not, it will not run correctly.

Any leak in the Y-S may be detrimental to excellent running and must be corrected

There would have to be an attempt to slightly pressurize the crankcase to check for leaks of the front seal which is located behind the front bearing and would leak at the front bearing?

petec

My Feedback: (58)

Is your engine plumbed exactly like this? I'm trying to figure out how you would be getting fuel out of the check valve line.

dmccormick001

This description is kind of hard to sort through, but I think I've finally understood that you took the fuel line going from the pressure side of the regulator to the tank's vent loose, and while filling the tank, fuel ran out. That indicates a non-working check valve. Fix that first, and make sure the valve is a YS brand check valve, the valves made by other companies, like Tettra for example, do not work correctly on a YS. The design is different and they just don't work right. With no check valve in place you're flooding the regulator with fuel where it isn't supposed to have fuel, I suspect some is probably making it's way under the diaphragm and into the crankcase, flooding it, and that may be the source of the fuel leak.

I'll bet your problem is much simpler that a bearing/seal issue. Go back to the basics, get them in order, and I'm betting it will start to straighten up.

David

DwightMann

I replaced the check valve and was then able to get it to run. It would not idle, so I began to turn the pump in. While making the adjustment, fuel would drip from the carb. I have turned the pump in about 1 1/2 turns and it will now idle down to 2300 rpm. Fuel no longer pours from the carb when the engine is not running.

I have seen notes that recommend adjusting the high speed mixture, then bringing the idle to 2000 rpm (
not 2100) to check the idle mixture. The engine runs very rough below 2300, do I need to keep playing with the mixture? Should it idle at 2000?