Author Topic: Engine blowing raw fuel. (Read 8831 times)

Paul Taylor · « **on:** December 07, 2014, 09:24:09 PM »

I have a LA 46 on my Nobler ARF. Runs great and hauls the mail.
My only complaint is after each flight I have raw fuel from the nose of the plane all down the side. It is SLY-Mee!

This engine is flip and fly. I have not touched the needle all summer. I did have to back it out three clicks today due to colder temps.

I hate to mess with a good running combo. I called my tech support friend and he agreeded. Just Fly It!

It might be blowing fuel out if the front of the motor.

Any feed back appreciated.

wwwarbird · « **Reply #1 on:** December 07, 2014, 09:34:11 PM »

Are you sure that it's raw fuel? Are you sure that's it's actually coming out of the engine and not a leak somewhere else?

Randy Cuberly · « **Reply #2 on:** December 07, 2014, 11:57:47 PM »

Quote from: wwwarbird on December 07, 2014, 09:34:11 PM

Are you sure that it's raw fuel? Are you sure that's it's actually coming out of the engine and not a leak somewhere else?

Yeah, I would ask these same questions! It's possible for and engine to run very wet nosed but I've never seen an LA46 do it!

It also is usually accompanied by hard starting due to crank case compression leaking during starting!

Sounds to me more like a fuel line or tank leak if it really is raw fuel!

Randy Cuberly

Chris Wilson · « **Reply #3 on:** December 08, 2014, 12:44:55 AM »

Dedicated overflow pipe on the tank not capped off properly and siphoning off?

Or could it be another plastic back plate leaking again?

Perry Rose · « **Reply #4 on:** December 08, 2014, 04:27:37 AM »

Remove all the plumbing and tank and pressure test them under water.

Bob Reeves · « **Reply #5 on:** December 08, 2014, 06:46:53 AM »

I use an automotive hand vacuum pump, don't have to remove anything just plug any open lines. Pull the supply line off the engine and plug it, leave the filter in so it checks it and connect the vacuum pump to the muffler pressure or fill line. Pump up a vacuum, if it holds you are good if it bleeds off you have a leak, then start checking the individual components to find what is leaking.

This is one from Harbor Freight that will do the job but better ones can be found.
http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-69328.html

This is kinda like the one I have but now they are allot more than what I paid. With this you can also pressurize the tank and it has a release so you can let the vacuum or pressure off.
http://www.harborfreight.com/mityvac-vacuum-pump-39522.html

bill rutherford · « **Reply #6 on:** December 08, 2014, 08:32:04 AM »

As this is a sleeve bearing you are most likely blowing the fuel out the front . I have seen it many times and there in not much you can do about it other than replacing the case. If it had ball bearings you could replace the front seal. Oh well the engine is cheap so no big loss. bill

john e. holliday · « **Reply #7 on:** December 08, 2014, 09:16:25 AM »

If we don't some blow by thru the crank shaft area, how are we going to lubricate it. As long as the engine is working don't worry about it.

Paul Taylor · « **Reply #8 on:** December 08, 2014, 09:37:22 AM »

Quote from: bill rutherford on December 08, 2014, 08:32:04 AM

As this is a sleeve bearing you are most likely blowing the fuel out the front . I have seen it many times and there in not much you can do about it other than replacing the case. If it had ball bearings you could replace the front seal. Oh well the engine is cheap so no big loss. bill

Yea I would think if it a fuel system leak I would not get a good needle setting. But I tach it and it's rock steady 9600 rpm.
Maybe Santa will bring me a new motor 😉

Steve Scott · « **Reply #9 on:** December 08, 2014, 09:40:04 AM »

Quote from: bill rutherford on December 08, 2014, 08:32:04 AM

As this is a sleeve bearing you are most likely blowing the fuel out the front . I have seen it many times and there in not much you can do about it other than replacing the case. If it had ball bearings you could replace the front seal. Oh well the engine is cheap so no big loss. bill

I bought a used FP 20 off eBay. The front shaft/sleeve bearing was so worn it was spitting raw fuel out the front of the motor.

Paul Taylor · « **Reply #10 on:** December 08, 2014, 01:14:43 PM »

Here is a photo. I have another 46 to try.

Garf · « **Reply #11 on:** December 08, 2014, 01:17:04 PM »

I would say it is a 90% chance it is a fuel leak somewhere. Some silicone fuel lines are prone to pinholes.

Paul Taylor · « **Reply #12 on:** December 08, 2014, 01:24:44 PM »

With a pin hole i would not think I would get the perfect engine run.

The picture does not show it but it starts a the nose.

Balsa Butcher · « **Reply #13 on:** December 08, 2014, 01:48:10 PM »

What prop are you running? When I ran the APC 12 1/4-3.75 (NW setup) it was puking fuel all over the place, much like the symptom you described. Switched to a smaller prop/higher RPM and it stopped. Go figure...

Jim Kraft · « **Reply #14 on:** December 08, 2014, 02:10:24 PM »

I do not know about the OS 46 LA, but many engines have a groove in the shaft bearing from a little behind the front to the rear of the bearing to let the engine suck residual oil and fuel back into the case. These can either not be cut all the way to the rear or be fouled from metal particles from the factory. Either one will make for a wet nose.

Richard Imhoff · « **Reply #15 on:** December 08, 2014, 03:27:54 PM »

The fuel tank has split seams if it's the metal tank that comes with the plane, have one on the bench now from Samantha's plane she was flying last summer.
Engine ran perfect but had short flight times. When you see red fuel residue it's NOT coming from the engine internally it's raw fuel from the tank.

Chris Wilson · « **Reply #16 on:** December 08, 2014, 06:48:21 PM »

Quote from: Paul Taylor on December 08, 2014, 01:14:43 PM

Here is a photo. I have another 46 to try.

Pretty much shows spiral airflow debated about elsewhere!

wwwarbird · « **Reply #17 on:** December 08, 2014, 06:49:42 PM »

Quote from: Paul Taylor on December 08, 2014, 01:14:43 PM

Here is a photo. I have another 46 to try.

The photo looks to me to be mostly oil. Maybe a little bit excessive but if it's running well and consistent I'd say just keep on flying it. How much time is on the engine?

Doug Moon · « **Reply #18 on:** December 08, 2014, 07:17:06 PM »

That looks like raw fuel to me.

I had a PA 65 on a clunk tank doing that a couple of years back. It ran perfect!!

I was running a clunk tank and the stopper was old and loose and it was pumping fuel out all over the place. I was running pressure so it only made the issue worse. The plane was covered after a flight.

I ran it on the ground with the cowl off and it showed me the leak instantly.

You might have a leak on your little plug there. Screws dont plug very well either as they have threads and they leak. A good thing to use is a bb stuffed into the line. Works like a charm.

david beazley · « **Reply #19 on:** December 08, 2014, 09:25:10 PM »

Is it a chinese LA46?

Motorman · « **Reply #20 on:** December 08, 2014, 09:54:33 PM »

Quote from: david beazley on December 08, 2014, 09:25:10 PM

Is it a chinese LA46?

LOL, best post of the day.

Grab the prop with both hands, rock it back and forth and feel for excessive play in the crank. A wet nosed engine will drop your fuel economy allot.

Some of these proprietary fuel mixes have cheap synthetic oil that will junk your bottom end prematurely. Pull the back plate and check for slop in the con rod.

MM

Andrew Hathaway · « **Reply #21 on:** December 08, 2014, 10:07:59 PM »

Last one of mine that did that needed a new O-ring on the venturi.

Dennis Moritz · « **Reply #22 on:** December 08, 2014, 10:13:24 PM »

Worn crankcase bushing would leak pretty raw fuel. I think the bushing in the la46 is only half depth. I've seen them wear out get cranky. But yours runs well. Could be you're at an optimum wear point. For the moment. Pull the tank out pressure test underwater. Silicon tubing looses its grip after a while. Mebbe that.

Sent from my iPhone using Tapatalk

Trostle · « **Reply #23 on:** December 08, 2014, 10:34:56 PM »

Put the engine on a test stand. I bet you will see the fuel is coming from the front bushing.

If it is, there are several thing you can do about it.

1. Get a new engine.

2. Replace the crankcase or put a new bushing in the one you have. Hard to do unless you are a machinist.

3. Etch some corkscrew grooves in the shaft to pull the fuel back into the crankcase. Again, helps if you are a machinist or have one to do it for you.

If it is not coming from the front end, check to see if the fuel is coming from the back plate. However, it would not run very well if at all if there is that much leaking. So check your tank and fuel lines. Good luck.

Keith

Dan McEntee · « **Reply #24 on:** December 09, 2014, 01:12:26 AM »

If it's thick and gooey, and you are using a fuel like SIG Champion with a Klotz and castor mix, it's probably just excess oil from the exhaust. If your usable fuel load is, or the typical amount of fuel you carry for the pattern (adjusted for temperature and air density) hasn't changed, it's excess oil, especially if you spike your fuel with extra castor. The goo on most of my models is tinted red like this, as I tend to use SIG Champion fuel. Unless you are un able to carry enough fuel for the pattern, I wouldn't worry about it. If it is as consistent as you say, I don't think it's broke and if it ain't broke, I don't fix it!
Type at you later,
Dan McEntee

John Rist · « **Reply #25 on:** December 09, 2014, 11:49:08 AM »

Tired of slime - go electric.

eric rule · « **Reply #26 on:** December 09, 2014, 08:23:39 PM »

What Keith Trostle suggested has a lot of merit.

We used to get this problem with the Fox .35. The crank shaft would wear the bushing in the front end and fuel would leak out. The way Larry Foster and I fixed this in over 1800 L&J fox 35's was to run a small groove just back from the front edge of the bushing. We tied this groove (made with a broaching tool) into the small oil spillway that was already in the bushing. This set up a low level suction which pulled the fuel back from the outer edge of the bushing. Problem solved in an easy and inexpensive way.

If the bushing is worn out I would have Jim Lee machine up a new bushing with the groove in it. This can be pressed into the front of the crank case to solve the problem.

Doug Moon · « **Reply #27 on:** December 09, 2014, 11:17:59 PM »

Quote from: eric rule on December 09, 2014, 08:23:39 PM

What Keith Trostle suggested has a lot of merit.

We used to get this problem with the Fox .35. The crank shaft would wear the bushing in the front end and fuel would leak out. The way Larry Foster and I fixed this in over 1800 L&J fox 35's was to run a small groove just back from the front edge of the bushing. We tied this groove (made with a broaching tool) into the small oil spillway that was already in the bushing. This set up a low level suction which pulled the fuel back from the outer edge of the bushing. Problem solved in an easy and inexpensive way.

If the bushing is worn out I would have Jim Lee machine up a new bushing with the groove in it. This can be pressed into the front of the crank case to solve the problem.

Eric,

You have a pic of the groove you made and the tool?

Thanks

Balsa Butcher · « **Reply #28 on:** December 09, 2014, 11:26:49 PM »

I'm going with what Dan said...designed in feature for your fun and enjoyment. Just a rich mixture, they don't call 'em "slimers" for nothing. For variety, use some of the new PowerMaster 10/22. Then the residue on your wing and fuselage will be purple rather than pinkish red. And the expression on the face of your your electrics only flying buddy when he retrieves your plane after a flight...priceless!

Steve Helmick · « **Reply #29 on:** December 09, 2014, 11:33:15 PM »

I've been told that VP has changed the latest CL mixes to include no dye, because Mark Scarborough complained about it ruining his award-winning finish. Well, I think that's what Mark said!

Anyway, if you want to get your 'lectric-only buddy's hands purple, you're gong to have to hurry.

Steve

Balsa Butcher · « **Reply #30 on:** December 10, 2014, 12:17:22 AM »

Mark complained about it, I complained about it, Brett complained it. They promise a fix is in the works. Meanwhile LHS still only has the purple stuff...whatever, I'm just glad to have a LHS that still carries 10/22, regardless of the color.

Dennis Moritz · « **Reply #31 on:** December 10, 2014, 10:35:27 PM »

Oh. It was dye. Got confusing. All those shades and colors. Couldn't keep track. Engines ran pretty much the same. Kinda sorta far as we could tell.

RknRusty · « **Reply #32 on:** December 11, 2014, 09:25:11 PM »

I bought two gallons of 10/22 from Bob Krug in October and they're clear now. It even says so on the can. Now I have a partial can of purple I don't want to use in my White Yak-9 so I always leave the stuff at home. It's not a nose bleeder but still leaves purple slime all over it.
Rusty

phil c · « **Reply #33 on:** December 12, 2014, 06:19:13 PM »

Quote from: Chris Wilson on December 08, 2014, 06:48:21 PM

Pretty much shows spiral airflow debated about elsewhere!

Actually, that looks more like the prop tip vortices blowing back along the fuselage. AKA all the pix of full size planes shown with spirals coming off the prop tips.

Howard Rush · « **Reply #34 on:** December 13, 2014, 01:54:47 PM »

Quote from: Chris Wilson on December 08, 2014, 06:48:21 PM

Pretty much shows spiral airflow debated about elsewhere!

Quote

Actually, that looks more like the prop tip vortices blowing back along the fuselage.

Straight down? If so, there's no flow over the wing, so the airplane wouldn't fly, just roll around on the ground.

And if you leave it in that position for an hour or so, it will be flowing straight up on the other side.

Everybody's a **&^ *&% aerodynamicist.

Chris Wilson · « **Reply #35 on:** December 14, 2014, 01:32:07 AM »

Quote from: Howard Rush on December 13, 2014, 01:54:47 PM

Everybody's a **&^ *&% aerodynamicist.

Nah, just us two.