Engine stops unexpectedly

[mch]

Hello all,

 

it's me again (simply because I'm still on the learning curve with my J400).

 

I seem to have a problem with my engine setup. This is what I can reproduce rather reliably:

 

Procedure:

 

1. Engine running at some speed above idle (say 1000 RPM)

 

2. Plane moving at more than 10 kts

 

3. Throttle back to idle

 

4. Decelerate the plane rapidly

 

Result:

 

Engine experineces a serious RPM drop below normal idle, this can even stop the engine.

 

I have first encounteres this behaviour when I decelerated from a speed taxi on the RWY (to get it cleared for the next plane).

 

Today I experienced the same when I went to idle after the round out while landing. So this was a glider landing with the prop nicely but stationary in front of me :)

 

My stationary idle is set at 900 RPM and there is no (real) way to overcome the idle stop, you would literally have to break something.

 

Also the fuel pump was on while landing and carb heat applied until in final. I do not think that the engine starved for fuel, had icing in the carb or that I closed the throttle beyond the stop.

 

Something else must happen systematically. I presume that the problem is that the prop acts as a "brake" when the plane decelerates quickly. This could force the engine below the "normal" RPM mark for a given power setting.

 

The strange thing is that this *never* happened during my "GA career" with a C172.

 

Has anybody experienced the same?

 

Can I do something to avoid that by a carb setting?

 

Of course I could learn to decelerate more slowly :)

 

The engine restarts immediately (with the starter, of cousre), with NO change in power setting. This also indicates that it is not an idle throttle problem.

 

Mike

 

 

[Captain]

Mike

 

Others don't do this so it is an issue with your engine.

 

I suggest that you check all sections of the idle circuit in the carby for intermittent or permanent blockages and the mixture of that circuit.

 

All it would take is a tiny piece of foreign material anywhere there to do what you suggest.

 

If it were me I would remove and clean all sections of the carby as the 1st place to start, and this is not a big task.

 

Then purge your fuel line.

 

Make sure that you catch anything that comes out of the carby or the fuel line (sieving thru a stocking or similar is a good way to do that .... and look out for small slivers if rubber from the fuel line that may have been cut when attached to metal parts).

 

Regards Geoff

 

 

[Modest Pilot]

Check for leaks around the sealing rings on the inlet manifold pipes. A leak down compressions check might also reveal something, hopefully not a cracked head!

 

 

[jacmiles]

Mch, check your instrument dash,if its flexing too much it effects your idle by moving your throttle cable in and out.

 

 

[jetjr]

Its quite easy to flex or bend throttle stops by applying too much force

 

JR

 

 

[Yenn]

Could be due to the rapid power reduction and movement.

 

I have had misfires if I reduce power rapidly while applying forward stick. and today had a stoppage from about 2300rpm while checking carby heat and the tail lifted. I cut the throttle rapidly, released the brakes and let it roll. Immediate restart and I couldn't replicate the event. Put it down to fuel sloshing in the carby.

 

 

[geoffreywh]

make sure that the throttle arm is coming up against the stop on the carb. and not hanging on the cable. I have seen aircraft from the factory where the idle has been set by the length of the inner cable and not by the throttle stop. The end result is that by pulling hard on the handle in the cockpit you can stop the engine.

 

 

[mch]

Hi,

 

took Geoff's advice and cleaned the carburetor today. The idle system was almost completely blocked. It was not a single piece of debris but sort of a greyish/white "mud". The other systems (choke and main) were clean.

 

It will take some time until I can flytest the "new" carburetor again but I think this looks like a plausible reason.

 

Will post one more reply when I know for sure that this was the cause.

 

Mike

 

 

[Captain]

Hi,took Geoff's advice and cleaned the carburetor today. The idle system was almost completely blocked. It was not a single piece of debris but sort of a greyish/white "mud". The other systems (choke and main) were clean.

 

It will take some time until I can flytest the "new" carburetor again but I think this looks like a plausible reason.

 

Will post one more reply when I know for sure that this was the cause.

 

Mike

Mike,

 

It's always nice to find something when you investigate a problem such as this, so you have had a good result.

 

With the carby clean it might also be worth your while to fit a new fuel filter if it was not renewed recently ............ and remember that any time you change out an oil or fuel filter, cut it open to see what is in there, as that can provide additional clues to what is going on.

 

Look forward to hearing whether this has solved the issue for you.

 

Regards Geoff

 

 

[Lowflyer]

Had exactly the same as this with my Jabiru 2200 in my Tecnam a couple of weeks ago. Engine stopped on pullback for final, glide approach was o.k.

 

On start up on the ground with throttle all was well, but on pullback for idle she went way past my normal 950 rpm and stopped.

 

I went for the slow running jet straight away and low and behold it was blocked.

 

There was also some very strange looking stuff in the bowl. I have a very effective gascolator and a new filter ,but this seemed to be something that had slipped the net looked maybe like something in the fuel additive.

 

Anyway after blowing through the idle jet with an airline and cleaning the bowl she came straight back to tickover.

 

I used to have this problem very occassionally with a Rotax 447 and the idle jet was nearly always the culprit.

 

Pleased that you found the answer as I did.

 

Roly Tecnam P92 Echo (pom flyer)

 

 

[Ross]

Are the pilots that are getting blockages in their carburetor jets using fuel with added ethanol?

 

It occurs to me that fiber glass fuel tanks with internal baffles, if they have them, would be particularly hard to slosh completely with tank sealant.

 

Any exposed glass would be subject to degradation from the fuel and it would probably end up in the small carburetor jets.

 

In my J160 kit #14 the original sealant was not suitable for use with fuel containing ethanol.

 

The hole saw cutout from one of the holes cut into one of the wing fuel tanks had an area about 40 mm diameter that was missing a layer of tank sealant making me very nervous about the integrity of the fuel tanks.

 

I do not know if the manufacturer had two lots of sealant applied - if so it may have been OK but there was still the area near the new holes in the tanks.

 

This was one of my incentives for sloshing my wing tanks which hopefully would allow the use of mogas if necessary and also seal around the additional fittings that are fitted by a kit builder, the tank filler hole and the drain hole.

 

There are plenty of old Jabs out there in Australia with wing tanks that are not suitable for use with ethanol added fuels.

 

 

[mch]

Hi Ross and Lowflyer,

 

at least for me that is true. I have used Mogas with up to 7.5% Ethanol (at least according to the fuel station at our field).

 

There was no visible debris in the bowl, that one was perfectly clean. The material that blockes the idle system appeared to be some sort of mud. Of course it takes not a lot of a mud film with these tiny orifices to block them.

 

Maybe the ethanol has washed out something from the fuel lines like water dissolves chalk. In that liquid form it could have passed the filted. Later, maybe when the engine is resting for days or a week, fuel evaporates in the idle sytem leaving that mud film. Like a coffee machine.

 

But I don't know for sure. I'm going back to Avgas, anyway.

 

Mike

 

 

[Lowflyer]

I have been using Mogas in this plane since owning her and the previous owner had done 150 hours using mainly Mogas.

 

This could be a problem with the fiberglass tanks,but I think this would have shown up earlier as the plane is 7 years old.

 

A friend who flys a flexwing had fuel starvation and found that the filter gauze was covered in a chalky substance. This was definitely an additive problem.

 

Over here in the U.K. I do not buy Mogas from supermarkets as it seems their suppliers are adding more ethanol than some of the major companies like Esso and Shell etc.

 

The Jabiru runs very well here on Mogas,so I am not in a hurry to change, but if I get much more problem with the idle jet blocking, then I would have to think again.

 

Roly (tecnam P92 Echo) Jab 2200

 

 

[Guest ozzie]

http://www.ultraflightradio.com/impodcast/2009/09/29/ufr090929d.mp3

 

This was from Roy's show last week. Ronnie Smith from Mississippi Light Aircraft talking on fuel contamination.

 

 

[Lowflyer]

re fuel contamination.

 

Many thanks Ozzie, a very interesting listen, scary as well.

 

Kind regards.

 

Roly.

 

 

[diablo]

Jabiru 2200 engine conks out on landing while rolling

 

Hi Mike,

 

I have exactly the same problem. On approach engine rpm is around 1400-1700, touch down and throttle back, she goes below 900 RPM and sometimes stops.

 

I have tried to reproduce the problem on the ground, but cant seem to. I have tried various levels of carb heat, mags and fuel pump settings,

 

I understand you cleaned out your idle jet system. Do you have instructions on how to do that? I would like to check mine out.

 

I do not use mogas on my engine, only avgas....

 

appreciated in advance

 

Dean

 

http://jabiru.iscool.net

 

 

[mch]

Hi Diablo,

 

you have do dismount the carb. The idle system consists of several very small boreholes in the main housing. These bypass the main air duct. The most effective way to clean these was for us this procedure: We removed the screw #7 (number of the screw in the explosion drawing of the carb). It is located on the bottom of the housing, very easy to find - made of brass.

 

We found quite some dirt already there.

 

Furthermore you can now easily check airflow in the idle system, because the boreholes pass the opening below that screw. Pour in some aceton or similar and then blow air into the opening. This presses the aceton through the boreholes and expels the dirt in there.

 

For us that worked fine. We did have a compressor, which eased the task :)

 

Before cleaning there was almost no airflow through the boreholes, afterwards one could blow through happily.

 

But I think you can do the same with "mouth air pressure" also, it will probably take longer.

 

I hope this solves your problem.

 

Mike

 

 

[icebob]

Hi,

 

We had a customer with a Rotax 582 with the same problem. He had coated the inside of his fuel tank BUT it is a f/glass tank and he had used a product called KLEM and the company specifically states it is not for f/glass tanks the upshot was a new tank, plus he did not change all the fuel lines to Ethanol resistant ones.

 

Bob.