engine quits
 

I have a new FP40 OS engine.The engine runs great it idle great on the ground has great power run great in the air .But when I go to land the plane and idel back and on final the engine quits and i have to dead stick it in . Some of the guy at the field says that i just need to run it more to break it in .I've ran it on a test stand for 3.5 tanks of fuel 2630cc {about1/2 a gallon } How much more or how to fix it.

RE: engine quits
 

G'day

Three and a half tanks of fuel is not a great deal. I think your club mates are on the right track, it is just not run in yet.

I would set your idle on the high side so it keeps running AND I would use a lower pitch prop so that it will still slow down to land. So if you are using a 10 x 6 which would be about normal for a plain bearing 40, try a 10 x 5 or 10 .5 x 5 and it should be fine while it is idling high.

One other thing to check, try tuning it with the tank about 1/4 full. It could be that it is just leaning out in flight and is a bit too lean at the end of the flight as the tank becomes empty.

Let us know how you go.

Mike in Oz

RE: engine quits
 

-The 40 FP''s as do all the FP series Have bleeder carburators. The number one mistake the fellows make with these is to not adjust the mid range adjustment at all because they do not know its there, where it is or which way to turn the screw.

Thats because its a screw in the front of the carburator that covers up a direct hole (facing forward) that goes directly into the venturi. This type of midrange adjustment is rare these days in modern engines and - it is backwards of all other midrange needle valves, unlike those others you unscrew it to make the mid range mixture leaner.

Talk to your mentors about this. Additionally you may have the fuel tank to spraybar relationship a little off. While there is a wide range to work with its best to start off with the center line of the fuel tank roughly level with the jet or spraybar in the carburator.

John

RE: engine quits
 

While a little more running time is a good idea (as is a lower pitch prop), I'd ask if your low speed needle is set just right. This is fairly easy to determine:

Let the engine sit at idle for 10 or 15 seconds
Advance the throttle to full QUICKLY
If the engine comes up smoothly to full throttle you're fine
If the engine quits very quickly on the way up, the low speed needle is too lean
If the engine coughs , spits and hesitates on the way up, the low speed needle is too rich

If you need to adjust the low speed needle to get that smooth transition, don't forget to readjust the high speed needle when you're finished.

Also, make sure your glow plug is good. Sometimes a weak plug can give you the same symptoms.

One other quick test that might help. When you start your engine let it run a few clicks above idle for 5 seconds then remove the glow starter. If the engine slows noticably you either have the low speed needle too rich or a weak plug.

This all sound more complicated than it really is. You'll get it ...... have faith! Best of luck

RE: engine quits
 

My 40 FP is dead reliable with the air bleed all the way open. You could probably just take out the screw. All my old air bleed carb engines need to have the hole wide open, Enya or OS. I would open it all the way, and then try the test above.

While it's possible the plug is weak, I doubt it. Break-in can weaken plugs, but those engines don't need a lot of break in; mine were always fine after break in, and I've had a variety of FPs.

Not sure why it idles well on the ground but not in the air, but check the bleed hole.

Jim

RE: engine quits
 

thanks for the information i'll give it a try and let y'all know what helps. thanks again.

RE: engine quits
 

Augie11 is right on the money!!
The only thing I might add to his advice is: If you do make any ajustments to the high speed needle, recheck the transition.
And then check it again!


-Johnny-

RE: engine quits
 

Also, when adjusting the low speed, go with very small turns. I normally do 1/12 of a turn and then fire up the engine to test.

RE: engine quits
 

I'd vote for the engine being tuned too lean. If it's exactly right on the ground with a full tank then it will be too lean in the air with a low tank. Tune your high speed needle to just off peak with the nose pointed up. That will be the leanest it'll ever run in the air and will put you a little rich sitting level. Then tune the air bleed for good idle and transition. If it won't idle for you for a minute on the ground then either your tuning is off or you have the idle set too low.

RE: engine quits
 

Guys, this is NOT A TWO NEEDLE CARB. As jester says, it is an air bleed carb. It doesn't have two interacting needles. Changing the air bleed adjustment has no effect on the top end needle adjustment because once the barrel opens the air bleed is closed off.

And his engine is not dying at high speed, it is dying on idle. It's good to hold the nose of the plane up to adjust the needle, but it's not going to solve his problem.

With air bleed carbs you don't necessarily get a minute of idle and then a great transition unless you've really got the right plug. With air bleed carbs, there often isn't much you can do with tuning to cure an idle problem because once the air bleed is all the way open, that's all you've got, and often the crankcase is STILL getting some fuel build up. Then you just have to have a glow plug that will stay lit when a slug of fuel hits it. The OS FPs work pretty well with the hole wide open if you have a good plug.

Jim

RE: engine quits
 

You are correct buzz. I blew it not realizing the FP is air bleed. My bad. Would a plug like an OS # F help him out? I know we've installed them on some balky inverted 2 strokes and they work wonders.

RE: engine quits
 

No problem Augie, I know I've goofed on these forums now and then.

It might help...never tried it. I've had smaller Enyas with bad transitions that were completely cured by an Enya #3 or McCoy 59 plug. On OS FPs I always had good luck with the OS A3 and a wide open air bleed, so maybe that will do the job for him. I expect we'll hear pretty soon.

Jim

RE: engine quits
 

To clarify, it's true the air bleed doesn't affect the high end, but the high end does affect the air bleed setting. It has to be set right first before he does anything to the low end. Cutting out upon going to idle from a higher speed does indicate a problem with either the air bleed setting or a bad or wrong glow plug.

RE: engine quits
 

I once fixed an OS LA (same kind of air bleed carb) by just knocking the dirt out of the airbleed hole :D. Probably not the issue in this case, but worth checking.

It's also possible that you're just trying to idle lower than the engine will. Do you have a tach to check the idle RPM?

When you idle on the ground, do you idle for the same length of time you do while on final? I've seen plenty of guys "test the idle" for a few moments, but not long enough to match what actually happens in the air. If the engine is slowing loading up on fuel due to being just a bit too rich, I would expect this to happen.

RE: engine quits
 

Perhaps he won't get to it until next weekend but I hope he let's us know. I haven't had an air bleed since an old OS .48 four stroke and I do remember cleaning those parts out did help.

RE: engine quits
 

Well I go to the field tomorrow .I've checked everything IS clean and I had put in a new glow plug on the last flight saturday and i checked it today glowing good .I'm going to flight my first flight wiht everything as it was saturday then Im going to do the adjusting .By the way i'm not idling the engine to slow it should still be running when i land,

RE: engine quits
 

OK Luke, good luck. Keep us posted.

RE: engine quits
 

Would drilling the air bleed hole out about 1/64 or 1/32 help at all?

RE: engine quits
 

I would remove the carb from the engine and find the drill bit that just fits into the air bleed hole. Then chose the next size larger and drill out the hole.

Clean up all the chips with glow fuel, reassemble the carb to the engine and try again/

It always improved the air bleed engines I have run in the past

RE: engine quits
 

Well I went to the field yesterday, First flight same thing engine quit when landing we adjusted the thrittle {high speed riched in it} went up egnine quit apon landing This time back flushed carb and installed a new glow plug again this is the thrid one for this engine and it's not even a month old any way back up engine ran a little better but still quit apon landing.One more try for the day added a filter to the fuel line at the carb guess what it worked got in two landing with the engine still running .I would have guessed but one of the best pilotsat my club said add a filter and that worked.I would like to thank everyone for the help and the come back .
luker737

RE: engine quits
 

The filter probably increased the amount of pressure differential required to move the fuel into the carb.

To me that indicates you haven't yet solved the original problem, which is likely due to PLUMBING or LOW SPEED needle settings, especially given the results with the filter in place.

RE: engine quits
 

I was thinking along the same lines. A filter prevents problems, it doesn't solve problems that were already there. But it could be making the engine run a little more lean.

Is the air bleed hole completely open? In your list of things you did, I didn't see anything about this.

Jim

RE: engine quits
 

We did check the air bleed hole and it is wide open we also rich the engine out some we are not seeing any exhust yet .I watch another fp40 and i could see exhust smoke from it but you can't see any from mine I don't know if this has anything todo with it just thought i would add this information.

RE: engine quits
 

You do normally see some smoke, but that's not a good indicator of your tune. What you are looking for is at WOT to be able to pinch the fuel line and hear a distinct rise in rpm's. If someone has a tach you can use, 500 rpm is generally good. Most of the time, if you then raise the nose of your plane like you're doing a loop, the engine will rise on its own to that point, telling you that you have a perfect tune in the worst case scenario for fuel draw, which means you're a touch rich everywhere else. A very common mistake with a bad running engine is to start tweaking needles without knowing what your mix is now. You should be able to get a consistent rpm with any needle setting, and be able to see a consistent rise in rpm as you go leaner, then it peaks and stays the same for a few clicks, then starts to drop as you get too lean. When the high speed is properly set, then go to the low speed. If the engine idles and steadily drops rpm until it quits, you're too rich, If it idles a bit and rises in rpm before dying, you're too lean. The rich idle will change sound not long before dying as it loads up with fuel, but it will also die like that with a bad glow plug, too low an idle, or bad fuel. The difference is that the engine sound will stay the same as the rpm's drop and then stop. Get the idle right at a throttle setting that will run for a while, then lower your throttle and recheck. Don't go for the lowest possible idle, just low enough to where the plane won't pull itself sitting flat on the ground. Then check transition. Let it run for a full minute, then gun the throttle open. If it stumbles and blows a little fuel out of the exhaust, you're too rich. If it hesitates, you're too lean. With some engines, you have to make a compromise between good idle and good transition, but on most the right setting will give you both. The last thing to do is to check the high speed needle one more time to be sure it's still right. Air bleed carbs usually won't need any other tweaking, but some engines will and it's good practice to make sure before flying.

All of this assumes that your engine does not have any air leaks or fuel supply problems and isn't worn out. Generally, once you get an engine set right the only adjustments it will need after that is two or three clicks of the high speed needle to adjust for different atmospheric conditions. If you find yourself needing more than that, there is usually something wrong that has nothing to do with your needles.

RE: engine quits
 

Went to the field yesterday first flight the engine ran fine for about 7 minutes then quit had to dead stick. We let the engine cool down some then fueled it up did some adjusting on the high speed needle then up we went this time the engine ran great could land and do tuch and go's and it kept running .Maybe we have it right it is a little rich right now but maybe a little more run time will let it be lean out .