paul_c

My Feedback: (6)

Ok guys, first I thought that there was a leak going to my 46FX. There are still some bubbles in the short line to the carb, but I don't think this could be enough to make the engine die like it does.

I've replaced the plug (A3); I thought it ran a little better with the glow starter on, but it still dies with the starter on, as well as off. I've tried different mixture settings, but it definitely isn't a lean/rich issue----not the way it dies suddently after running strong.

It is as if a kill switch has been flipped the way it dies.

Like I said, there seem to be a VERY small amount of bubbles coming from the needle valve (haven't been able to solve that mystery either) but I don't think this can be the cause of the engine suddenly dying.

dbow

My Feedback: (1)

Your needles settings should be at about 2 turns on the top end and about 1 turn on the bottom end.

When you make needle changes take your time and allow the engine to run first before making another change. With the settings above you should not need to make much adjustment other than leaning the top end out to the max then backing off a little.

If it still acts funny with the proper needle settings I would pull out the main needle and flush the line with some fuel, then flush out the carb with fuel.
Then check the tank and be sure that its at the proper level to the carb and does not have any leaks. Fuel line can be checked also to ensure no nicks or holes.

Goodluck

Dbow

paul_c

My Feedback: (6)

Again, I'm pretty sure there are no needle setting issues, BUT I have been testing the engine with the tank out of the fuse, and the tank is sitting quite a ways BELOW the engine (since it is on the ground). Maybe this could be it.

If not, how do a flush as you suggested?

Thanks

paul_c

My Feedback: (6)

New finding--engine only dies when glow starter pulled.

(i will repost)

Tattoo

I always carry a spare tank in my field box for just such occasions. Rubberband it to the side of your fuselage, and run your engine again. This will immediately let you know if you have a tank problem, such as a pin hole in a line, kinked clunk line, or something like that. If your engine runs great...time to pull the tank. If your engine does the same thing...time to keep troubleshooting the engine.

C_Watkins

My Feedback: (10)

The bubbles in the line are an issue, and do need to be addressed.
The line is for fuel only, and settings will always be whacky with bubbles there.
Most common cause is a leaky remote needle valve. They are worthless.
Remove the needle, and replace the O-rings if equipped. If not, slip a
small piece of fuel tubing over the needle and screw it back in. (will help seal it)



However, your current problem of dying only when glow removed is due to
a "too rich" problem, or a bad glowplug. You may be too rich at idle because
you've had to tweak the engine rich to compensate for those bubbles, yaknow

Try another new plug (even if you already have) if leaning doesn't help.

TailDraggin

My Feedback: (5)

An OS #8 plug may help. It's a little more expensive, but what is normally recommended for break in of that engine.

paul_c

My Feedback: (6)

Ok everybody: the engine check was done with the tank out of the fuse--no leaks there.

I tried using smaller tubing (which seems to have helped) AND I bought and replaced the tiny O ring around the needle valve. Still seems to be some leaks ORIGINATING from the needle valve area (b/c bubbles only seen in the line to the carb).

If I am still rich, has anyone seen this with the needle vavle open ONLY ONE TURN? I did pinch the line and the rpms did go up, but I got worried, thinking how can I be rich if only open ONE turn?

Also, are there supposed to be two (or one) O-rings on the needle valve? If only one, then I've found the problem.

C_Watkins

My Feedback: (10)

While unusual, for sure... be less concerned with the number of turns out,
and more concerned with performance. Even though you haven't touched the
low end, as you said... it could be out too far to begin with. Not unheard of.

For the RNV... cut some pieces of tubing to go over the fittings on top of the
regular tubing. (To act as a clamp of sorts) Fit the pieces over your needle nose
pliers, remove the fuel tubing from the needle, and expand the small pieces
enough to slide up over the tubing. Then put the tubing back on the needle.
Should be a very snug fit at that point. If it still leaks, who knows. I hate RNV's


Hearty "second!" to the OS #8 plug, by the way.
I've seen no better plug for most of the "normal" engines we use.

DBCherry

My Feedback: (4)

Paul,
If this is the way your testing the engine, it is most certainly the problem!

Your fuel tank centerline needs to be even with the spray bar in the carb for things to operate correctly.

Dennis-

paul_c

My Feedback: (6)

Dennis, I did prop the tank up so that it is approximately the same level as the engine, and things are better, but still dying out. I don't know how the tank would be completely level anyway, b/c the piper sits "back" on its tailwheel, and even the tank is canted upward towards the engine (i.e. not parallel with the ground)

David Cutler

Bubbles in the fuel is a bad sign and will cause a problem. It makes it impossible to set the mixture properly, and needs to be fixed.

Is the fuel tank sufficiently isolated from vibration? it should be vibration free, or bubbles will be created.

-David C..

Parkerm

My Feedback: (6)

Check needle valve, I have seen needle vales that leak enough air to take the engine lean. It is an intermittent problem in some cases.

paul_c

My Feedback: (6)

I really think it is the needle valve. But I put a new O-ring on today. LESS bubbles, but still some; you know what? I put TWO O-rings on, and the bubbles stopped altogether, but then I couldn't screw the needle valve far enough down to lean it out. So I know there is only supposed to be one O-ring.

I wonder if this problem would have ever developed if I didn't take the needle valve out (which I had to do to cut out a cowl for my Cub)

MILDBILL-RCU

My Feedback: (6)

try sealing the pressed & threaded fittings that are on the remoted needle block........(the one's that the line's push on to), my 46 was sucking air through the pressed in one. i used thin ca glue to do the sealing. been fine for the last 3 years with no more trouble..........good luck!!!!!!!!!!!

Homebrewer

My Feedback: (8)

Are you using a FRESH NEW GALLON OF FUEL?
Did you replace the fuel tubing inside the tank?
Do you have the carb connected to the correct line out of the tank (feed line, not the pressure line?

If so, and the engine has good compression and no loose bolts on head or backplate then it can only your needle setting.

If you can get your engine running for even a bit, immediately go to the fuel line and squeeze and release it in rapid succession while hearing what occurs to your engine (leave glow on). By manually controlling fuel flow you can determine if your needle settings are too rich.

HOOTER

Try putting a check valve in pressure line from muffler, I had a 46 fx doing the same thing, turned out muffler was leaking and not enough back pressure to fuel tank. Welded seams in muffler [roblem solved.

TailDraggin

My Feedback: (5)

My 46 FX kept dying during the early run-in process after about a minute or so, but by the end of the third tank of fuel was fine.
Didn't stop me from removing the tank and flushing it out, in case there was some debris left in the (new) tank).

paul_c

My Feedback: (6)

Bob_NJ, one of the moderators on the forum, helped me out at the field today. It turns out the engine may have been dying from bad fuel (although the fuel seems to work in my trainer plane). He put some S & W 5% fuel in, and the plane ran without quitting.

Thanks Bob, and thanks to all for the advice.

Paul

bob_nj

My Feedback: (62)

When you get the new thrust washer, try the other fuel just as a control measure. Stop by again, or maybe I can get to your field.
Take care_bob

paul_c

My Feedback: (6)

Bob, I may have found the source of the small amount of bubbles: remember how I couldn't get that one engine mount screw in? In trying to turn that screw, I noticed that I had ground down the lip of the fuel outlet/nipple that comes off the needle valve with my screw driver. So, new thrust washer coming in the mail, as well as a fuel outlet.

I'll let you know how it goes with my Omega fuel.

Thanks again, Bob.

bob_nj

My Feedback: (62)

Keep me posted_bob