Author Topic: Multiple Engine Problems !! (Read 1209 times)

Paul Raley · « **on:** May 08, 2025, 01:31:40 PM »

I have been having engine run issues with two planes that just about have me whipped! One setup is a Gieseke Nobler with an Aero Tiger 36 and the other is a T-Bird with a Brodak 40. Similar issue with both planes. Typically the engine will start fine, needle well on the stooge, take off and fly a lap or two (or a few more), then cut off like the fire went out. I will then try and restart which it will do easily, remove the glow starter and the engine dies. I have been through at least a dozen glow plugs (Fireball, Sig, Thunderbolt, Enya #3) and tried new fuel (Brodak 10%N 11 1/2% Castor 11 1/2% Syn). Tanks have been flushed. Both engines are very good condition...although I did have a very brief shaft run on the AT36 when I did a ground run in the yard when the prop and spinner came loose (rats!). Why am I killing glow plugs? Any suggestions? I have been flying off and on for forty years and this has me stumped! TIA

Dan McEntee · « **Reply #1 on:** May 08, 2025, 01:50:50 PM »

Gonna need to know a lit more but will ask some questions. Are the plugs actually bad afterwards? Will they work in a known, reliable set up? If you have tried alternate fuels, and the problem is common to two separate models with different engines, my guess it's something in your installation of the engines, tank, and fuel line plumbing. I suggest solving one mystery first and then apply anything learned from that to the other airplane.
Type at you later,
Dan McEntee

Colin McRae · « **Reply #2 on:** May 08, 2025, 03:53:51 PM »

I'm just shooting in the dark here, but are you running muffler pressure to the fuel tank?

I had a similar problem on one model where I was using Sullivan silicon tubing for the muffler pressure line. I normally use the pink tubing from Brodak. The Sullivan tubing is very flexible compared to the Brodak pink tubing. What was happening was during flight the very flexible Sullivan tubing was bending and kinking reducing fuel flow by pinching the muffler pressure line as it flexed. The engine was going very lean. Excessive lean operation can kill a glow plug.

I switched out to the stiffer pink tubing and the problem went away. Now I'm being much more careful with all my engine related plumbing.

Paul Raley · « **Reply #3 on:** May 08, 2025, 05:05:49 PM »

Quote from: Dan McEntee on May 08, 2025, 01:50:50 PM

Gonna need to know a lit more but will ask some questions. Are the plugs actually bad afterwards? Will they work in a known, reliable set up? If you have tried alternate fuels, and the problem is common to two separate models with different engines, my guess it's something in your installation of the engines, tank, and fuel line plumbing. I suggest solving one mystery first and then apply anything learned from that to the other airplane.
Type at you later,
Dan McEntee

Dan,
The AT 36 was a good setup ten years ago. The T-Bird was re-engined with a B40. It's the glow plug thing that has me scratching my head. The only fuel i have access to is Brodak. I did buy a brand new quart which is what I used today. The plug will only work with the glow starter attached after it dies in flight. At least right away. I will try the setup in the yard tomorrow and see if they are still dead or if was a temporary thing. All new fuel tubing. In line filters removed in case they were leaking. One tank new but both flushed with alcohol. Running uni-flow w/o muffler pressure. Using Sonic-Tronic glow starter. I think your advice to tackle one at a time is a good one.

Paul Raley · « **Reply #4 on:** May 08, 2025, 05:08:51 PM »

Quote from: Colin McRae on May 08, 2025, 03:53:51 PM

I'm just shooting in the dark here, but are you running muffler pressure to the fuel tank?

I had a similar problem on one model where I was using Sullivan silicon tubing for the muffler pressure line. I normally use the pink tubing from Brodak. The Sullivan tubing is very flexible compared to the Brodak pink tubing. What was happening was during flight the very flexible Sullivan tubing was bending and kinking reducing fuel flow by pinching the muffler pressure line as it flexed. The engine was going very lean. Excessive lean operation can kill a glow plug.

I switched out to the stiffer pink tubing and the problem went away. Now I'm being much more careful with all my engine related plumbing.

Thanks Colin. In my case I am using new Brodak pink tubing w/o muffler pressure. Engines don't lean out before they quit...really weird!

Motorman · « **Reply #5 on:** May 08, 2025, 09:18:30 PM »

Maybe you have a chunk of solder floating in your tank. You get in the air and the chunk finds it's way to the block the fuel pick up in a couple laps. But really sounds like bad glow plug or leaking head gasket but, on both engines? Too many head shims? Are these brand new in package plugs you're trying. You know the Brodak 40 runs cold. You need a thick heavy dirty prop to put some load/heat on it. might just be going up and cooling off to much causing the flame out. Maybe the fuel maker is skimping on the nitro?

MM

Paul Raley · « **Reply #6 on:** May 09, 2025, 06:52:39 AM »

Quote from: Motorman on May 08, 2025, 09:18:30 PM

Maybe you have a chunk of solder floating in your tank. You get in the air and the chunk finds it's way to the block the fuel pick up in a couple laps. But really sounds like bad glow plug or leaking head gasket but, on both engines? Too many head shims? Are these brand new in package plugs you're trying. You know the Brodak 40 runs cold. You need a thick heavy dirty prop to put some load/heat on it. might just be going up and cooling off to much causing the flame out. Maybe the fuel maker is skimping on the nitro?

MM

Thanks Motorman. The plugs are new in the package. I am going to pull the heads to see how the piston and liners look to see if there could be any carbon or other bits killing the plugs. I do have some alternative B40's and AT36's to try as well. This is a strange one...

Ken Culbertson · « **Reply #7 on:** May 09, 2025, 07:07:11 AM »

I am not the engine expert that you are getting really good tips from here, one of the reasons I went electric after 50 years of IC. So, for my 2 cents, the problem is in one of three places. My approach would be to eliminate two of them and work on the third. Not counting you as a cause there is the plane, the engine/tank and the "engine in the plane". So far, the advice has all been focused on the first two. So, have you tried taking the engine out of the plane and see if it will run out a tank on a test stand with a simple clunk tank. If it does, then try restarting. If that is a Yes/Yes, then try again with your tank. Still good then we now know it is the planes. What is common? In my experience engines only quit without going lean from overheating, flooding and hitting a bird. Are the motors cowled? Try flying without the cowl. That should eliminate overheating and you have now reached the limits of my expertise. Besides centrifugal force, what can cause inflight flooding?

Electric motors don't have glow plugs!

Ken

PS - if cowled, is the inlet for the air large enough to cover the cooling fins and is the outlet at least twice the size and relatively unobstructed. Which T-Bird? Upright engine or inverted cowled?

Colin McRae · « **Reply #8 on:** May 09, 2025, 08:23:23 AM »

Another shot in the dark.

Might your venturi effective area be too big for the particular engine? Lots of modelers try to use large venturi's with the goal of boosting power, but it ends up not being a good idea for a stunt application. A venturi that is too large on vent will not pull fuel properly, go lean, and overheat.

Using muffler pressure may help with an oversized venturi as it boosts fuel draw, but the real cure is a properly sized venturi.

Something like a 0.265" ID throat venturi (in a spray bar application) would be appropriate for these size engines.

Paul Raley · « **Reply #9 on:** May 09, 2025, 08:24:16 AM »

Update: I was able to get full tank runs on both setups in yard just holding the airplane outside wing down. In addition, the glow plugs that refused to keep the engines running with the battery off yesterday at the flying field worked fine today! I think these engines/tanks are possessed. I did pull the head on the AT36 and there was a small speck of carbon that fell off the combustion chamber that POSSIBLY messed with the glow plug. Maybe tank issues are causing or adding to the in-flight cut off problem?

Paul Raley · « **Reply #10 on:** May 09, 2025, 08:27:22 AM »

Quote from: Ken Culbertson on May 09, 2025, 07:07:11 AM

I am not the engine expert that you are getting really good tips from here, one of the reasons I went electric after 50 years of IC. So, for my 2 cents, the problem is in one of three places. My approach would be to eliminate two of them and work on the third. Not counting you as a cause there is the plane, the engine/tank and the "engine in the plane". So far, the advice has all been focused on the first two. So, have you tried taking the engine out of the plane and see if it will run out a tank on a test stand with a simple clunk tank. If it does, then try restarting. If that is a Yes/Yes, then try again with your tank. Still good then we now know it is the planes. What is common? In my experience engines only quit without going lean from overheating, flooding and hitting a bird. Are the motors cowled? Try flying without the cowl. That should eliminate overheating and you have now reached the limits of my expertise. Besides centrifugal force, what can cause inflight flooding?

Electric motors don't have glow plugs!

Ken

Thanks Ken. Both setups ran fine in the yard today (ground run) using the same glow plugs that gave problems yesterday! I will try flying them without cowls. The T-Bird in the 59 inverted and cowled version. Thanks for the advice!

PS - if cowled, is the inlet for the air large enough to cover the cooling fins and is the outlet at least twice the size and relatively unobstructed. Which T-Bird? Upright engine or inverted cowled?

Paul Raley · « **Reply #11 on:** May 09, 2025, 08:28:57 AM »

Quote from: Colin McRae on May 09, 2025, 08:23:23 AM

Another shot in the dark.

Might your venturi effective area be too big for the particular engine? Lots of modelers try to use large venturi's with the goal of boosting power, but it ends up not being a good idea for a stunt application. A venturi that is too large on vent will not pull fuel properly, go lean, and overheat.

Using muffler pressure may help with an oversized venturi as it boosts fuel draw, but the real cure is a properly sized venturi.

Good point. I do have smaller venturis for the B40 I can try. The muffler has a pressure port as well. Thanks!

Colin McRae · « **Reply #12 on:** May 09, 2025, 08:45:11 AM »

Quote from: Paul Raley on May 09, 2025, 08:28:57 AM

Good point. I do have smaller venturis for the B40 I can try. The muffler has a pressure port as well. Thanks!

I would measure the throat ID on what you have and go from there. If they are already something close to 0.0265" then the venturi size is probably not the problem. And try muffler pressure as a comparison test.

Even stock venturi's that come with a CL engine can be too big for a good stunt run. Case in point. I have an EVO 36 that came with 3 different size venturi's. Even the small ID one was way too big. Jim Lee sells a smaller ID one for the EVO 36. I purchased one and it transformed the engine. It now runs great on vent alone.

One other idea. If your venturi uses a spray bar be sure the spray bar outlet hole is pointing straight down into the intake which is the lowest pressure zone at the venturi throat.

Dan McEntee · « **Reply #13 on:** May 09, 2025, 11:19:36 AM »

Quote from: Paul Raley on May 09, 2025, 08:24:16 AM

Update: I was able to get full tank runs on both setups in yard just holding the airplane outside wing down. In addition, the glow plugs that refused to keep the engines running with the battery off yesterday at the flying field worked fine today! I think these engines/tanks are possessed. I did pull the head on the AT36 and there was a small speck of carbon that fell off the combustion chamber that POSSIBLY messed with the glow plug. Maybe tank issues are causing or adding to the in-flight cut off problem?

OK, that should bless the components individually, I think. I still think that since you have a more or less identical problem in two models, and you built/assembled/set up both models at the same time, it's something common that you did to both airplanes.

I have seen guys coming back into the hobby ( affectionately called "retreads!") get excited and in a rush to get back into the air, fall back on something that we don't necessarily do anymore. Do you have offset in the engine, rudder and adjustable lead outs? Since these are new airplanes, you might have gone too far with the offset stuff, and have the airplane flying excessively nose out. I have chased my own tail over the years trying to solve a quirky engine issue and finally realized the airplane was flying so far nose out, that when the fuel load goes down in the first few minutes of flight, the fuel load follows the now slanted front out tank wall, and the fuel will actually run away from the pick up due to centrifugal force. It will lean out and act funny at first and probably overheat, and then just shut off. This is how coffin type tanks work on speed models. Hand the model from it's lead outs and see how the fuselage lays. it should only be a degree or two nose down. If sliding the lead outs forward will help that, do so, but make sure they are still about in line with the balance point or a fuzz behind. Then fly the airplane carefully and see what you get. You can adjust side thrust and rudder offset as you get into final trimming. I try to build a full fuse model so it is possible to cant the back of the tank outwards and if ne3cessary, build or modify the tank so the front is a bit narrower than the back.. It's easy to do on a profile, just shim the tank. I seriously doubt there is a common problem with both engines that are of different brands.
Type at you later,
Dan McEntee

Paul Raley · « **Reply #14 on:** May 09, 2025, 03:43:31 PM »

Quote from: Dan McEntee on May 09, 2025, 11:19:36 AM

OK, that should bless the components individually, I think. I still think that since you have a more or less identical problem in two models, and you built/assembled/set up both models at the same time, it's something common that you did to both airplanes.

I have seen guys coming back into the hobby ( affectionately called "retreads!") get excited and in a rush to get back into the air, fall back on something that we don't necessarily do anymore. Do you have offset in the engine, rudder and adjustable lead outs? Since these are new airplanes, you might have gone too far with the offset stuff, and have the airplane flying excessively nose out. I have chased my own tail over the years trying to solve a quirky engine issue and finally realized the airplane was flying so far nose out, that when the fuel load goes down in the first few minutes of flight, the fuel load follows the now slanted front out tank wall, and the fuel will actually run away from the pick up due to centrifugal force. It will lean out and act funny at first and probably overheat, and then just shut off. This is how coffin type tanks work on speed models. Hand the model from it's lead outs and see how the fuselage lays. it should only be a degree or two nose down. If sliding the lead outs forward will help that, do so, but make sure they are still about in line with the balance point or a fuzz behind. Then fly the airplane carefully and see what you get. You can adjust side thrust and rudder offset as you get into final trimming. I try to build a full fuse model so it is possible to cant the back of the tank outwards and if ne3cessary, build or modify the tank so the front is a bit narrower than the back.. It's easy to do on a profile, just shim the tank. I seriously doubt there is a common problem with both engines that are of different brands.
Type at you later,
Dan McEntee

That is the thing Dan. Both of these airplanes were successfully flown in contests 15 to 20 years ago. I had them dialed in quite well at that time. The T-Bird did have a AT36 originally but at 43 oz I was thinking that a B40 would pull it just fine. I did check the leadouts just as you recommended. It must primarily be a tank issue. I hate to do it but may have to pull the backs off to check the tubing. Thanks for your advice!

Brett Buck · « **Reply #15 on:** May 09, 2025, 03:47:17 PM »

Quote from: Paul Raley on May 08, 2025, 01:31:40 PM

I have been having engine run issues with two planes that just about have me whipped! One setup is a Gieseke Nobler with an Aero Tiger 36 and the other is a T-Bird with a Brodak 40. Similar issue with both planes. Typically the engine will start fine, needle well on the stooge, take off and fly a lap or two (or a few more), then cut off like the fire went out. I will then try and restart which it will do easily, remove the glow starter and the engine dies. I have been through at least a dozen glow plugs (Fireball, Sig, Thunderbolt, Enya #3) and tried new fuel (Brodak 10%N 11 1/2% Castor 11 1/2% Syn). Tanks have been flushed. Both engines are very good condition...although I did have a very brief shaft run on the AT36 when I did a ground run in the yard when the prop and spinner came loose (rats!). Why am I killing glow plugs? Any suggestions? I have been flying off and on for forty years and this has me stumped! TIA

I would try a name-brand fuel (Powermaster). Whenever I have encountered this issue, it always came down to fuel. It is very frustrating problem for which I have never seen even a plausible, much less definitive, explanation. I assume that something is getting deposited on the plug element.

By the way, Fireball plugs are pretty infamous for other failure modes, but not this one. I would avoid them. I have used only Thunderbolt and S&H Type F, with a few OS plugs, for many many years now, and have had exactly one failure.

Brett

Paul Raley · « **Reply #16 on:** May 09, 2025, 05:20:27 PM »

Quote from: Brett Buck on May 09, 2025, 03:47:17 PM

I would try a name-brand fuel (Powermaster). Whenever I have encountered this issue, it always came down to fuel. It is very frustrating problem for which I have never seen even a plausible, much less definitive, explanation. I assume that something is getting deposited on the plug element.

By the way, Fireball plugs are pretty infamous for other failure modes, but not this one. I would avoid them. I have used only Thunderbolt and S&H Type F, with a few OS plugs, for many many years now, and have had exactly one failure.

Brett

Thanks Brett. Based on your suggestion I just ordered some VP Powermaster Aviation fuel 10%N and 18% Syn/Caster blend. Do you think I should add some additional oil (I have castor and synthetic) to run in an AT 36 and B 40?

Brett Buck · « **Reply #17 on:** May 09, 2025, 05:45:35 PM »

Quote from: Paul Raley on May 09, 2025, 05:20:27 PM

Thanks Brett. Based on your suggestion I just ordered some VP Powermaster Aviation fuel 10%N and 18% Syn/Caster blend. Do you think I should add some additional oil (I have castor and synthetic) to run in an AT 36 and B 40?

No, just run it straight out of the can. I have run that fuel almost exclusively for about 25 years, mostly in a single AAC engine, with absolutely no issues. And in any case, "adding something" may induce the problem.

And be careful! This phenomenon happens every now and then, very unpredictably, and has definitely resulted in several wrecked airplanes.

Brett

Paul Raley · « **Reply #18 on:** May 10, 2025, 09:15:48 AM »

Quote from: Brett Buck on May 09, 2025, 05:45:35 PM

No, just run it straight out of the can. I have run that fuel almost exclusively for about 25 years, mostly in a single AAC engine, with absolutely no issues. And in any case, "adding something" may induce the problem.

And be careful! This phenomenon happens every now and then, very unpredictably, and has definitely resulted in several wrecked airplanes.

Brett

Thanks for the advice Brett. Fuel does seem like the likely culprit...especially since both engines were similarly affected. I am keeping my fingers crossed.

Dave_Trible · « **Reply #19 on:** May 11, 2025, 07:42:07 AM »

I had the same problem with my one and only AT .36. Put it in a new plane and never could keep it running long enough to get to the handle and take off. I did break the engine in on the stand and didn't experience the issue. Of course it was upright on the stand- inverted in the airplane. Tried several different plugs including my fav Glow Devil and even Fox trying to get something hotter but to no luck. The fuel I used in everything else with no problem. Wouldn't think the 22% oil would have been a problem but who knows. In any event I put a Merco .40 in, sold the engine and all is well now.

Dave

Paul Raley · « **Reply #20 on:** May 11, 2025, 02:35:17 PM »

Quote from: Dave_Trible on May 11, 2025, 07:42:07 AM

I had the same problem with my one and only AT .36. Put it in a new plane and never could keep it running long enough to get to the handle and take off. I did break the engine in on the stand and didn't experience the issue. Of course it was upright on the stand- inverted in the airplane. Tried several different plugs including my fav Glow Devil and even Fox trying to get something hotter but to no luck. The fuel I used in everything else with no problem. Wouldn't think the 22% oil would have been a problem but who knows. In any event I put a Merco .40 in, sold the engine and all is well now.

Dave

Interesting! Maybe I own your AT 36 now! It was second hand....LOL

Dave_Trible · « **Reply #21 on:** May 11, 2025, 06:44:49 PM »

Well I don't think so but it is interesting you are having the same issue. I'd bet Brett may be close to the issue. I think If I still had it I would back down on the oil percentage and also lean towards more synthetic oil. I have seen a few newer engines that totally balked at castor oil-to my amazement. OS .32F I recall was that way and maybe Thunder Tiger .42 to some degree. I really don't understand why that is but somebody can explain it I'm sure. I'd rather just use engines that are more friendly to my normal methods.

Dave

Brett Buck · « **Reply #22 on:** May 11, 2025, 10:33:24 PM »

Quote from: Dave_Trible on May 11, 2025, 06:44:49 PM

I have seen a few newer engines that totally balked at castor oil-to my amazement. OS .32F I recall was that way and maybe Thunder Tiger .42 to some degree.

The best example is the Evolution 36 - which more-or-less required low-percentage synthetic oil to run properly as delivered. This was dutifully recorded in the directions. Naturally, almost everyone ignored that, tried to run GMA or something like it ("real stunt fuel"), and found that the venturi was "way too big". No kidding, the viscosity of GMA might be 25-50% higher the recommended Cool Power, of course it won't draw fuel.

Add to that the tendency to gum everything up, this can be a real issue, even on huge engines. One example was someone who managed to gum up their Jett 76 with excess castor to the point it wouldn't cold-start, and was jamming with the piston halfway up. You don't want to take something with maybe .0005" cold clearance, and fill up the gaps with glue.

I emphasize again, I am not at all sure about the cause of this "shut off like you flipped a switch" problem, aside from if appearing to be a fuel issue, or if running Powermaster will avoid it. If you could still get "Byron" Classic, that ALWAYS fixed this issue, every time we tried it. And I ran it at the NATS for several years, pouring it into an old SIG jug to hold down the jokes. The idea above is to get fuel that is a known quality instead of an off-brand more than getting less oil. My engine will not reliably run on GMA, or anything equivalent to GMA - severe misfires at the bottom of inside loops (and maybe other places tpp, but I never tried it because I chickened out after that).

If this doesn't work, I will tell you my next proposed step - take out the cylinder/piston and crock-pot them back to bare metal.

Brett

Dave_Trible · « **Reply #23 on:** May 12, 2025, 06:54:08 AM »

Life was better when there was Byron's fuel....used it forever and really miss the stuff.

Dave

Rusty · « **Reply #24 on:** May 13, 2025, 02:10:13 AM »

I agree with Brett. I think it is fuel. I had a brand new gallon of Sig 25% that was worthless. Nothing would run right using it. Try some different fuel.

Paul Raley · « **Reply #25 on:** May 16, 2025, 09:48:17 AM »

Quote from: Brett Buck on May 11, 2025, 10:33:24 PM

The best example is the Evolution 36 - which more-or-less required low-percentage synthetic oil to run properly as delivered. This was dutifully recorded in the directions. Naturally, almost everyone ignored that, tried to run GMA or something like it ("real stunt fuel"), and found that the venturi was "way too big". No kidding, the viscosity of GMA might be 25-50% higher the recommended Cool Power, of course it won't draw fuel.

Add to that the tendency to gum everything up, this can be a real issue, even on huge engines. One example was someone who managed to gum up their Jett 76 with excess castor to the point it wouldn't cold-start, and was jamming with the piston halfway up. You don't want to take something with maybe .0005" cold clearance, and fill up the gaps with glue.

I emphasize again, I am not at all sure about the cause of this "shut off like you flipped a switch" problem, aside from if appearing to be a fuel issue, or if running Powermaster will avoid it. If you could still get "Byron" Classic, that ALWAYS fixed this issue, every time we tried it. And I ran it at the NATS for several years, pouring it into an old SIG jug to hold down the jokes. The idea above is to get fuel that is a known quality instead of an off-brand more than getting less oil. My engine will not reliably run on GMA, or anything equivalent to GMA - severe misfires at the bottom of inside loops (and maybe other places tpp, but I never tried it because I chickened out after that).

If this doesn't work, I will tell you my next proposed step - take out the cylinder/piston and crock-pot them back to bare metal.

Brett

Success! I just flew three flights with near perfect engine runs. It was the fuel. All the difference with VP 10% Air (old Powermaster) 18% oil fuel. Many thanks for all the great advice. Now I can get back to practicing the pattern after a ten year break. I was almost ready to through in the towel...

Ken Culbertson · « **Reply #26 on:** May 16, 2025, 10:43:51 AM »

Quote from: Paul Raley on May 16, 2025, 09:48:17 AM

Success! I just flew three flights with near perfect engine runs. It was the fuel. All the difference with VP 10% Air (old Powermaster) 18% oil fuel. Many thanks for all the great advice. Now I can get back to practicing the pattern after a ten year break. I was almost ready to through in the towel...

Don't worry about the pattern. It is like riding a bicycle. You will get 90% back in a few flights. The remaining 10% is tough.

Ken

Paul Raley · « **Reply #27 on:** May 16, 2025, 01:14:04 PM »

Quote from: Ken Culbertson on May 16, 2025, 10:43:51 AM

Don't worry about the pattern. It is like riding a bicycle. You will get 90% back in a few flights. The remaining 10% is tough.

Ken

Thanks Ken! I did all the under 45 deg stuff today...but forgot my sunglasses, and it was really sunny, so the full pattern attempt will have to wait until i remember my sunglasses or it's a cloudy day!

Brett Buck · « **Reply #28 on:** May 16, 2025, 03:33:15 PM »

Quote from: Paul Raley on May 16, 2025, 09:48:17 AM

Success! I just flew three flights with near perfect engine runs. It was the fuel. All the difference with VP 10% Air (old Powermaster) 18% oil fuel.

Glad it worked out for you! I am not sure if it was just the erzatz fuel with whatever it has, or just too much oil - I suspect the latter, because I don't know what you could put in fuel to make it happen otherwise. I

A lot of old engine "knowledge" or advice may have been accurate when someone came up with it, but is not correct or disastrous now. Engines (good ones, anyway) are vastly different than they used to be, and people still keep using old fuel ideas, sometimes picking the engine or saying it is good or bad depending on how well it runs on ancient "real stunt fuel" ideas. The Evolution 36 example was the most obvious case, but far from the only one.

My condition would probably compel me to start adding oil to the Powermaster fuel until the problem repeats itself, that would at least tell you if it was just excess oil (which it certainly is) or it's something else in the Brodak fuel beyond just the oil. But that's a dangerous experiment and I certainly don't recommend anyone intentionally try to recreate the problem, at least not with any airplane you want to keep for long.

Brett

Steve Helmick · « **Reply #29 on:** May 16, 2025, 07:25:48 PM »

Post #1 indicates glowplug problems...did that mean they were burnt out, or just changed because they were perceived to be NG?

If they're "burned out", one cause can be from aluminum being worn away somewhere. The crankpin rubbing on the backplate, front of crank disc rubbing on the casting, etc. I've had it happen on an OS .35 Max III (crank bushing not located correctly in the casting) and K&B Series '61 .35's, when the crank pin migrated out (pressed in pin) to rub on the backplate. Using an electric starter on a sleeve bearing engine will do it, if the thrust washers are not installed or not thick enough to keep the back of the rod and crank pin from dragging on the backplate.

Steve

Paul Raley · « **Reply #30 on:** May 17, 2025, 04:32:01 AM »

Quote from: Steve Helmick on May 16, 2025, 07:25:48 PM

Post #1 indicates glowplug problems...did that mean they were burnt out, or just changed because they were perceived to be NG?

If they're "burned out", one cause can be from aluminum being worn away somewhere. The crankpin rubbing on the backplate, front of crank disc rubbing on the casting, etc. I've had it happen on an OS .35 Max III (crank bushing not located correctly in the casting) and K&B Series '61 .35's, when the crank pin migrated out (pressed in pin) to rub on the backplate. Using an electric starter on a sleeve bearing engine will do it, if the thrust washers are not installed or not thick enough to keep the back of the rod and crank pin from dragging on the backplate. Steve

Steve what I since found with the glow plugs was that they would partially "come back to life" after playing dead at the field. After they would die in flight I could immediately get the engine to start again at the field but it would die as soon as the glow driver was removed. The last time this happened I tried the same glow plug the next day and the engine would run with the battery removed but with some rpm drop. I am guessing there was some deposit from the bad fuel that evaporated or somehow diminished over time. In any case I don't seem to be getting the problem with the VP fuel. A weird one!

Brett Buck · « **Reply #31 on:** May 17, 2025, 12:11:30 PM »

Quote from: Paul Raley on May 17, 2025, 04:32:01 AM

I am guessing there was some deposit from the bad fuel that evaporated or somehow diminished over time. In any case I don't seem to be getting the problem with the VP fuel. A weird one!

Again, this is also exactly what we (David F. and myself, among many others) have found, Powermaster has much less tendency to form "taters" or put deposits on things than a lot of fuels, and will also remove deposits, including varnish, with extensive use. SIG Champion used to be the standard but we had all sorts of problems with it in the larger engines, including rapid tater formation. SIG Syn-Power did not do this at all, so, as has seemingly plagued stunt over the years, I suspect that the castor oil is the culprit. My guess is that is many sources of castor are contaminated with something else, or, something about the feedstock itself- the beans.

In the one case I tracked down (the Red Max "all castor is bad" hoax/scam) the issue was that they got some castor that was contaminated with Xylene, which had the effect of causing white flakes to precipitate out after about a week. This was apparently a production flaw, when their supplier was producing the oil, they would squeeze it out, get some oil, then add a solvent - xylene - to wash more oil out of the bean. They then heated/boiled off the results to get rid of the solvent. Apparently, the boil-off process was either cut short or somehow not effective, leaving the solvent behind, which when mixed with nitromethane, cause some decomposition in the form of the flakes. About the same time, we had a spate of both inexplicable wear-out issues with numerous engines, and a spate of "quit like you flipped a switch" problems just like yours.

I won't belabor the rest of the "situation", it was a long time ago, but I would characterize their response to this knowledge was "less than idea", which more-or-less made their name "Mud" in the stunt community.

The solution was to run other brands of fuel. SIG, about the same time, had some other problem that got resolved, mysteriously, in future production runs, aside from the "taters". For me, after endless pain trying to figure it out, including wiping out my airplane days before the 1996 NATs with a "mysterious flameout" problem like yours, the solution turned out to be Byron fuel. It was very weak for a stated nitro content, but always ran extremely well. We ent back to SIG after it got fixed, then moving to larger engines, ran into the tater issue, then switched to Powermaster which solved all the problems we had been having. This was a long time ago, late 90s, but there have been absolutely no issues since.

Brett

Steve Helmick · « **Reply #32 on:** May 19, 2025, 04:56:37 PM »

Yesterday, a club member had a similar problem with an FP .40, which I gathered was an ABN version. Two laps and quit, one lap and quit, 1/2 lap and quit, etc., etc. Changed various things, put a filter in the line between the tank and spraybar, deleted the rear NV, no change. Finally changed to some sort of green fuel and it ran fine...until it smashed the turf.

This is strange to me. When I got my first OS .46LA, I flew it after one run on the ground in the model, running Powermaster 10-29 all castor. When that gallon of 10-29 was gone, I changed to 10-22 half castor "GMA" blend. Ran fine on both, and other than reduced slime on the model, there wasn't a big change, except longer run time. Ran fine the last time I flew it...VSC 2009.

Steve

Brett Buck · « **Reply #33 on:** May 19, 2025, 07:16:57 PM »

Quote from: Steve Helmick on May 19, 2025, 04:56:37 PM

Yesterday, a club member had a similar problem with an FP .40, which I gathered was an ABN version. Two laps and quit, one lap and quit, 1/2 lap and quit, etc., etc. Changed various things, put a filter in the line between the tank and spraybar, deleted the rear NV, no change. Finally changed to some sort of green fuel and it ran fine...until it smashed the turf.

It seems to be very dependent on which specific engine you have. I had the same issue with two *identical* PA40s, and I can assure you that if Henry Nelson and Randy put them together, "identical" really means what it says. I also measured everything about it, I got *identical* readings. One engine ran on any fuel I tried with no issues. The other engine would flame out at random like you flipped a switch, same fuel, same everything, to varying degrees depending on which alternate fuels I tried. The only thing that was safe enough to fly it with was Byron 15% "Classic". I exchanged it with a different *identical* engine from Randy, that one was fine. Apparently, it kept doing the same thing when Randy had it, we never figured out what the problem might have been.

Brett