Good engine runs gone bad???

Help! I was getting great engine runs with my ST46. No changes made; same tank, no muffler pressure, fuel ( clean filter ),prop. All of a sudden, engine will not run smooth, changes rpm +/- 400 without touching the needle. On the ground and in the air, runs are the same.I did notice air bubbles in the fuel line.Are these the cause, or are they caused by the uneven run? I checked for hole in fuel line, cleaned spraybar-n/v. What next?

Is anything loose? Engine back plate, Mounting bolts, Out of balanced prop. Venturi gasket, Change glow plug, Landing gear tight?
If not, sounds like fuel. Good fuel can go bad. Try an ALL CASTOR. I know that your engine has a ring maybe it's time to have that replaced.

Scott(just some ideas)Riese

You don't say whether the bubbles were there before or not. Assuming that this is new, maybe something has come loose (bulkheads, engine mounting bolts,...., or as Scott notes, a new unbalanced prop) in the nose area which is causing more vibration, which then causes the fuel to foam. Also as noted elsewhere on the forum, some fuels tend to foam more than others, so have you changed fuel brands. Usually 4 drops of Armorall in a gallon of fuel will minimize this problem.

Engine was recently re-worked by T/L. I use all castor fuel, with armorall. Tried 2 different brands of fuel.Prop is balanced, all nuts and bolts are tight. Do not recall whether bubbles were present before, did not pay attention to fuel line with good runs. Just put everything back together after checking, new fuel line/filter, glow plug. Going to go fly, taking another plane just in case!

Have you tried running the engine on a sturdy test stand? Maybe the structure of the airplane is causing a problem.

>Engine was recently re-worked by T/L. I use all castor fuel,
>with armorall. Tried 2 different brands of fuel.Prop is
>balanced, all nuts and bolts are tight. Do not recall
>whether bubbles were present before, did not pay attention
>to fuel line with good runs. Just put everything back
>together after checking, new fuel line/filter, glow plug.
>Going to go fly, taking another plane just in case!

Keep us posted. The info that you gather might help someone later.

Further sugestions:
Assuming you have done the usual change of plug, checked everything for leaks and flushed the tank with acetone to disolve any castor "plugs" which can play games in the feed pipe.
1.To test if the airframe structure is causing this, run the motor on the ground then get both hands and take solid hold of the nose to see if the run settles. Hold/release/hold/release etc.
2.If you are running pressure ensure the block off on the overflow isn't split.
3.Run it without the spinner especially if it is plastic. They can get strangely out of balance at times causing the symptoms described.
4.If you are running an ST type NVA try an Enya style. Sometimes if the collar on the ST type isn't realy tight you can get the symptoms you describe.
5. Add some head shims to standard. Standard is meant to be 20thou but if you are using cap head screws the soft alloy of the standard shim can compress to 17 or so thou. Run 30 thou to start with to see if it fixes it and if it does, reduce the clearance till the run gets fussy again, then go up 3 or so thou.
Hope that's of some help.

Maybe a tank leak? All good suggestions above. You are wise to find and fix the trouble rather than keep flying and hopeing it will get better.

LAST EDITED ON Jul-11-04 AT 11:59 AM (CDT)
 
You know, you might want to look at your fuel situation.

Tigers don't really like all-castor fuels for lomg term use. 50/50 castor/synth fuels run cleaner and will keep your ring from sticking.

Also, you might try an OS NVA. Big Jim ( The one time King of Tiger tech.)used to swap out the stock NVA 'cause he thought that the stocker tended to vibrate in the rpm range that the STs like to run in. That resonant vibe would upset the engine run.

BUT! If you have bubbles in your fuel line, you have either a fuel line leak, a tank leak or a vibrating front end. If you have already swapped out your old silicone tubing, try this stuff.

1) If you have an in-line filter between your tank and NVA, remove it. Those things frequently either leak or vibrate, causing problems.

2) Check your tank for split fuel lines. Brass lines can harden and fracture.

3) Take a good look at your front end. You might have a fractured motor mount or another structural problem.

Once you locate the source of those bubbles in your fuel line, you probably solve your immediate problem.

Those bubbles point the way!

Bigs

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

LAST EDITED ON Jul-11-04 AT 01:05 PM (CDT)
 
Back from test flight after cleaning, checking everything. Same fuel, same result. ( 10/29 ) Tried another fuel, steady run, flight good. Let it sit while I flew back-up plane. Re-fueled with "good" fuel, no needle change, steady run, got half the pattern in, and it went lean. Not lean enough to mess engine up, but to fast to fly rest of pattern. I use a filter on engine and when fueling, so trash should not be a factor. Outside temp. may have caused lean run, it's 90+ deg. here. Going to the shade in back yard to try other suggestions. Thanks for the ideas.

LAST EDITED ON Jul-11-04 AT 12:07 PM (CDT)
 
Waite a minute!

Trash COULD be a problem if your filter is partialy blocked!

Also Tim Gee has some good sugestions. If you have a spare or better still NEW tank, swap it into the plane and see if that helps. Then, open up your present tank and see whats going on.

It's all in the details!

Bigs

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

LAST EDITED ON Jul-11-04 AT 12:22 PM (CDT)
 
Spitfire 1,
I have been running the ST 46 for a few years now and have had the same problem in the passed. Mostly occured after I let the plane sit for awhile. What I found was that the stock sprinkler venturi the one with the groove all around, well anyway the oil (caster) that was left in the groove after the last time I flew started to get thick or coagulate and give unpredictable runs. Also sometimes dirt gets stuck in the groove and causes problems as it floats around blocking the different holes and won't pass through. Other that that the only other thing I experienced was bad fuel line in the clunk tank (old) and of course that was my fault.

LAST EDITED ON Jul-11-04 AT 05:49 PM (CDT)
 
>Back from test flight after cleaning, checking everything.
>Same fuel, same result. ( 10/29 )

I know Tom is adamant about running all castor in his reworks, and I always have. He does work on the ring groove to virtually eliminate "ring sticking" problems when he installs the new Bowman ring. So I have never experienced sticking over the last 10+ years. I have found that Sig 25% all castor to work a little better than 29% around here. If it wasn't a T&L, I would not use the all castor.
After I have let it set for a long period of time, I always clean the entire fuel system, including removing the NVA and venturi and pulling the back off the tank. I do put a tiny dab of silicone on the inside face of both *nuts* on the NVA to help seal it to the case. Just be careful to apply a very small amount so than none enters the inside of the intake stack and let it partially set up before giving it the final snug. Other than that be careful that the hole in the spray bar is facing the groove in the venturi as accurately as possible. All of this I am sure you know, but it helps me to write it and re-enforce my memory! LOL!!
Good Luck!
Bill <><

Might have solved the problem. I was using an in-line filter, the clear one with two screens. Thought I had it clean. There is a certain fuel out there with "stuff" floating around in it. This stuff is almost clear, and sticks to the wire screen very well, almost forming a thin film over filter. Used more air pressure, and a wad of "stuff" blew out. Also, I use clunk tanks, and can see that plumbing, etc. is ok. ( took it apart anyway )Structure of nose is solid.Will run again later, already too hot in the shade.

What kind of fuel would have stuff floating in it. Or is it good fuel gone bad? with too much moisture? or what?? please share.

LAST EDITED ON Jul-11-04 AT 03:30 PM (CDT)
 
There have been some posts about SIG fuel having funny clear-ish "stuff" (snot?) floating around in it. Some have said it's from the plastic jugs, others say it's the castor oil.

I don't have a LHS that carries SIG, so I use Powermaster. No problems, like it a lot. But if he's using 10-29, then it's probably Powermaster. Scott had a bad can of Powermaster, that was literally a bad can...leaky, and had problems with running it in his Larry Foster McCoy .40. Don't remember the rest of the details. Scott, was the fuel defective also, or did some alcohol evaporate and make the mix bad, or what all????? Steve

>There have been some posts about SIG fuel having funny
>clear-ish "stuff" (snot?) floating around in it. Some have
>said it's from the plastic jugs, others say it's the castor
>oil.
>
>I don't have a LHS that carries SIG, so I use Powermaster.
>No problems, like it a lot. But if he's using 10-29, then
>it's probably Powermaster. Scott had a bad can of
>Powermaster, that was literally a bad can...leaky, and had
>problems with running it in his Larry Foster McCoy .40.
>Don't remember the rest of the details. Scott, was the fuel
>defective also, or did some alcohol evaporate and make the
>mix bad, or what all????? Steve
>
>http://www.nwskyraiders.com/index.html

Well it was a can of bad fuel and POWERMASTER replaced the fuel and engine.....end of story. There was less then 10% oil.

Did not get to run engine later today. Went to help my daughter fix up the room for my soon to arrive grandaughter. ( Yes, I'm proud !! )Fixing to be 50, looking forward to being " GRANDPA ". Do not want to name fuel, even though I know there is a problem with "trash". Have heard that others have already started straining this fuel. Fuel might not be the cause of my problem, but it is the only problem I have found so far. Will work on it more later. Thanks again for the help. By the way: Congratulations to the USA team!!!!

Have you checked your belt buckle latelly? Perhaps a Jimi Hendrix buckle will get you up and flying higher with more consistancy than your previous experience!!---JUST PERHAPS!! < Paul

LAST EDITED ON Jul-11-04 AT 09:49 PM (CDT)
 
In past years, there have been problems with trash in our fuel.

Taffinder, (When he was alive.) traced it to non-virgin Nitro. It seems that nitro is used in a cleaning process (For Fabric?) and then resold. The microscopic bits of fiber end up clogging our fuel systems. Reclained nitro is commonly used in glow fuel because of price. If your fuel is mixed with Pure Bakers AAA castor, that component shouldnt be a problem.

The solution is to double filter your fuel on the container side before it gets into your tank. I've done this for years and it works. Then you can elininate the crap trap filter in your fuel line because the junk never gets into your tank.

As I said before, crap traps tend to leak air as they age and the tubing hardens. They are also large enough to cause a vibration problem. The tiny two-part aluminum filters work better and have the advantage of having a cleanable/replacable superfine screen. They also don't leak.

I've used fuel that was stored in plastic jugs for as lone as five years without problems. It aint the jugs.

In-line filters can drive you crazy (Or crazier!)

Bigs

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

>Taffinder, (When he was alive.)

Hey Bigs,
Doug and his wife are alive and well. He was just forced out of the fuel business by the EPA, and a bout with skin cancer. But he is still kicking and promised to be at our local contest in October to judge when I saw him last month at Brodak's.
Bill <><

OMG!

Now I owe him an apology..!

Who else didn't die?

Bigs

"Snake Plisken! We heard you were dead!"

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

LAST EDITED ON Jul-12-04 AT 10:01 AM (CDT)
 
"In line filters can drive you crazy!" Yep, and they will cause your engine to go lean, die, and the plane fall straight down on top of you like a "lawn dart". Happened to me at Brodaks. I repaired the plane that night, no problem. The trouble was found by Kent Tysor very quickly-fuel filter was not tight and full of junk, looked like little grains of sand, but was old castor. It dissolved in Acetone. I kept it in the filter to see what would happen after I got home and in the shop.I now use "crap traps" and toss them after ten flights. Too much junk can get into the tank and engine from the asphalt where we fly. I was curious if it was sand or castor.
As to fuel problems, I did have one gallon can of Powermaster that was consistant in that my engine runs were all lean, no matter where the needle was at launch. Got rid of the fuel, no more problems. I have used a fuel by "Coopers" which has been great stuff. I have four gallon jugs, plastic, from Sig and all four leak fuel and oil on the bench. I have them off the floor, out of the light, in a fairly cool place. The other Sig jugs don't leak. I think it is happening at the seams.

I first noticed the "contaminant" floating around on and near the bottom of the fuel jugs. It appears to be a sandy colored material. Sorta like a small sandstorm blowing around in the bottom of the fuel jug. The fuel was Fox Super Fuel and Fox Dukes fuel. I bought some Sig and found it there also. I bought some Red Max and it was there also. One of the fuel manufacturers said to add some Klotz and it would dissolve. That was wrong!!! It just makes it harder to see.
My solution was to allow the fuel to sit for a couple of days and then without moving the jugs any more than necessary (to avoid stiring the "contaminant" up) syphon off the clear fuel down to about an inch above the "contaminant". Caution!! keep the syphon tube well above the "contaminant" I usually buy at least four gallons of each type of fuel, and do that with each gallon. I then shake up the remaining fuel in each jug and pour it into a single jug and allow that to settle out and again syphon that off down to about an inch above the visible "contaminant". That usually permits me to salvage 3 and 3/4th gallons out of the original four that is very clean. Of course, I syphon it off into CLEAN, well rinsed jugs and filter it into the jugs as it is being syphoned off. When drawing the Clean fuel out into my flight box fuel can, I run it through TWO filters, and through two more when fueling my plane tank and then there is a filter in the plane's fuel line.
I tried using some of the fuel that had the CRUD floating around in it last year and immediately started having run problems.
What to do with the remaining quart of heavily contaminated fuel???? It won't kill weeda, ants, grass, nor is it good for anything else. I may try to burn it in an oil burner heater next winter.

Bigiron

pour it through a coffee filter ??

I poured all of the fuel I had, opened and sealed, through paint strainers with a coffee filter on top. You would not beleive the
"stuff" left in the filters. This will be a regular thing everytime I buy fuel, regardless of brand. Coffee filters are cheap, engines are not! Thanks for all the input, all good ideas and things to try, turns out it was BAD FUEL! I will also do away with inline filters, and use a filter when fueling up.