I am having some fuel issues with my OS .46 engine. It is installed in a World Models Mach 1 plane. It has not been right since I crashed my last model in the dirt. The engine was cleaned out thoroughly with WD-40. The engine can be started but the turning the high speed needle has no effect. I assume I am getting too much air in the carberator. The engine runs to a point if primed well. I do not think I am getting enough fuel in the line.


I have a three line tank. I have one line going into the carberator, one into the exhaust, and on that is capped off where I fill the tank. One other odd thing is I can fill the tank but I can not pump the fuel out. Has anyone had this situation before? Any help would be greatly appreciatted?

You should be pumping the fuel out using the line going to the carb. If you can't pump the fuel and your engine will only run on a prime then you either have a tear in the fuel pick up line in the tankagainst the nipple or your clunk has been thrown foward and is up against the top of the tank. My guess is the clunk is wedged forward in the tank.Shake the plane a little and see if you can hear the clunk tapping in the tank. If you do then you probably have a hole in the fuel line and will need to remove the tank and put in a new pick up line. Sometimes if the clunk is stuck a good shake will free it up.

How is that third line plumbed does it also have a clunk on it? Does it have a brass pipe that goes to the rear bottom of the tank? Or is there just a straight and short tube that only just goes through the bung and stops?

If its like that last you will not be able to completely empty the tank from the fill third line. A three line system on an airplane with an exposed engine like that with only cheek cowls is overkill and only adds unneeded complexity. Its to late now since you already punched the third hole in your tank but do consider for those airplanes like that on the next one a very simple two line system with a break in it.

What Ratshooter is saying about checking the clunk for being pinched forward is dead on and checking all airplanes for a pinched internal clunk is the first order of business when a firm arrival has occured.

John

Im thinking that you may have your fuel lines routed wrong. On a 3 line tank, 2 of the lines should have clunks on them, and the third going to the muffler should be pointed up inside the tank. If you cannot suck fuel out of the tank, you may have the carb line and the pressure line reversed.

You may very well be lean....turn your high speed needle all the way closed...then back out 3 turns and see what happens...then tune from there

You may very well be lean....turn your high speed needle all the way closed...then back out 3 turns and see what happens...then tune from there

The high speed needle at this point have little or no effect on the engine at this point.

I will try swapping the carberator and exaust line. I think I will have to dump the fuel somehow to make surethat I can hear the clunk. I tried shaking the plane. I am not sure if that helped or not. It sounds like the engine has good compression.

Pull the tank out of the plane and replace all of the fuel lines. I would say that 90% of carb problems are fuel tank/line problems. It only takes a pinhole in a fuel line to mess things up. Check after each "hard landing" also. I only use 2 line tanks so can't comment on that part of your problem. If you cant get fuel to easily come to the carb inlet, there is no sense in even trying to start the motor. Blow into the line that goes to exhaust and fuel should rush out of the line that goes to carb. If not, fix this before trying to start the motor.

Re-plumb the tank- start from basics, open the stopper, figure out which line goes into which and reassemble the tank. Use fresh tubing for the three connections

Check the LSN first- if it was moved while cleaning the engine, take it back to the factory position. I think its 1.5 turns out from fully closed with the carb fully closed but do check with the manual

Tune the HSN with the engine running at WOT starting with 3 turns out from fully closed and slowly close till it goes to max rpm. Then open back a 1/8th turn.

Another thing you can do is to check whether the black o-ring around the carb is still in place.

If you still have no response from the engine, problem lies elsewhere.

Ameyam

If your going to re-plumb the the lines, go to a two-line system. On a Sky Raider Mk I (or II), you don't need a 3-line system. Always try to run as few lines to/from the fuel tank as possible - the more lines, the higher the probability for additional issues.

If you have a fully cowled engine that's a different situation, but even then a lot of times the lines area accessible and only 2 lines are necessary.

Hogflyer

I put the line that was on the carberator on the exhaust and exhaust to the carberator. I am going to fuel the lines with fuel to make sure I could bleed all the air out. If necessary I will pull the tank out then. I just need to go down the feild when it is not too windy to do some testing.

G'day

Another thing to remember - if the Low Speed Needle is tuned too lean, the engine may not start AND/OR the High Speed Needle will be ineffective. If you pulled the LSN out to clean things, you may have put it back too far? Try opening it a turn or two if all else fails.

I have been given several engines by people who could not get them to run. In all cases, the LSN was simply screwed too far in. Another I bought on eBay was the same.

Mike in Oz.

This is a preferred method to plumb and fuel a simple airplane with an exposed engine or just cheek plates.

That third nipple is sealed. If your tank already has a third hole in the plug I would just put a short piece of line on it and plug it. Fueling with a split in the carb line like this with a short piece of fuel tube is a good practice and there is no chance of flooding the carb. In addition in the case of a rear needle carburator its makes replacing the line far easier than trying to slip it back on the nipple in that tight space between the firewall and the engine.

also this method requires no additional internal tubes or extra clunks.


John

I prefer the 3 line system. This way I do not have to remove the line from the muffler to fuel my plane. This way I dont have to worry about tearing my line on the barbed fitting on the muffler. It is much easier to pull a plug from the fill line (third line) than to work the line off a barbed fitting.

Diverherb,
No matter how many lines you use, you do not need to remove the muffler pressure line to fill or empty the tank. In a two line system, the line to the carburetor is used for fueling and defueling.

dertwosubsw2,
Shaking the plane to hear the clunk rattle doesn't always work. My brother had a clunk fall off. It rattled just fine but the line was floating on the fuel and the engine died when it got above the fuel level.

The only way to know what's really going on inside the tank is to take it apart.