Procedures for clogged injector or turbocharger failure

[FloridaMan]

I was reading through the manual for the TSIO520 a couple days ago and noted something. I brought it up to my A&P and he mentioned the procedure is the same for a clogged injector. I'm not sure that I would've caught the latter if this were to have happened in my M20F and I figured I might not be the only member here who could've missed this procedure. 

The manual for the TSIO520 mentioned that in the event of a turbocharger failure, you're supposed to adjust the mixture to full lean and then slowly advance it until the engine runs. Otherwise the mixture may be too rich for the engine to run, could load the exhaust up with fuel, or cause other issues. It also said to not attempt to restart the engine with the starter above 20,000ft as you could damage the magnetos (I'm guessing because they would not be pressurized in that case and you could have destructive internal arcing). My A&P friend mentioned the clogged injector would cause the other cylinders to run excessively rich. I'm not sure why -- either airflow or the fuel servo would be metering for all cylinders and the fuel would be shared among fewer. 

[kortopates]

I personally don't see any similarities between loosing a turbo charger and a clogged injector. First off, recognize clogged injectors happen at different various levels of clogging. Its the small obstruction at takeoff that is the concern or troublesome. While a severe clog is going to reduce power in that cylinder to the point of being below 65% or even cease combustion.

So what you need to be primed for is responding to partial clog on takeoff or in full power climb. Its not going to make your other cylinders too rich but the one cylinder will be too lean driving up both that cylinders EGT and TIT. As a result the one cylinder is in danger of detonation from the reduced FF to it at high power. (If you see the high EGT become erratic and drop off while CHT escalates its in detonation with severe harmful IPC levels.) With a partial clog keeping the cylinder still near peak or on the ROP side at high power, CHT will be escalating to well above 400F quickly; and even faster north if detonation begins. So your action is to reduce power ASAP to avoid the escalating CHT and chance of a pre-ignition event taking over. Quickly reducing power to under 65% power will ensure the cylinder is not harmed and you'll still have the other 5 cylinders producing normal power enabling you to not to continue on but get you down safely without rushing. If a clog appears in cruise its that much more easier to deal with since it will be that much easier to get power below 65% to avoid harmful high CHT escalation; plus you'll have more time to recognize it more likely as a escalating CHT. Again a severe clog with just take the cylinder offline from going too lean. (Loosing one of 6 cylinders may not be that noticeable, but 4 cyl rajay installation would be a whole other matter!) 

A couple of times I have noticed a partial clog occur in a cylinder during the runup by seeing an abnormal increase in EGT as RPM is brought up with throttle; a high EGT that is not erratic or not from misfire. If you catch something like this don't takeoff unless you can get it too clear. To attempt to clear, go to full power with brakes on and see if the full fuel pressure/fuel flow clears it or not. If it does, your good to go. If not taxi back - you just averted risking destroying a cylinder and possible takeoff emergency by being tuned into your engine analyzer.

Regarding a turbo charger failure. Keep in mind this is much greater emergency than you may realize because it may include a huge exhaust leak ready to create a fire which is the greatest eminent threat at altitude. Once spooled down, its very unlikely you'll get it re-started again till the lower teens anyway, which is now just to help you make it to your emergency airport of landing. But yes, without the turbo spinning and the simplicity of the TCM fuel injection which doesn't regulate FF based on air density, the FF will be much too rich and will require more MAP than available at high altitude before you'll have much chance of getting it restarted; even with a leaned mixture.

What is a bit similar to loosing a turbo-charger is loosing the engine driven fuel pump, since with the loss of a fuel pump you loose the ability to regulate FF based on throttle - you have to be careful to accompany throttle changes with mixture changes. Depending on the airframe/engine you may also loose the ability to get sufficient FF for full power with only the aux pump as well.

Edited June 12, 2018 by kortopates

[N201MKTurbo]

When a turbo charger fails it is like putting the choke on, on a carbureted engine. it puts a big restriction in the airflow ahead of the fuel servo which jacks up the fuel metering making it super rich.

This procedure is for keeping the engine running in this situation and has nothing to do with clogged fuel injectors.

[N201MKTurbo]

FWIW,

When you are at turbo altitudes, your glide distance is huge. The chance of making it to an airport is very good!

[1964-M20E]

If the prop is still spinning the magnetos will still be firing assuming they were firing before the engine quit regardless if you have a turbo or not.  I'm not sure what trying to start the engine with the starter would have to do with that.  Now maybe the propeller will not windmill at higher altitudes I have not been that high to find out.  However, if I did have an engine failure and was trying a restart I'm going to let the prop windmill for that attempt and then if unsuccessful and have to put it down somewhere I'll try and stop the windmilling for greater glide if needed.

I have done a restart in the air already when I intentionally ran one tank dry on a long flight and yes I did lean the mixture before switching tanks so the engine would not over-speed when it started getting fuel again.

[FloridaMan]

This needs to be discussed here. I'm ok with getting flamed for it, but one failure mode with a fully clogged injector can result in the other cylinders running too rich. The treatment is the same as for a turbocharger failure. Getting 3 cylinders back online is better than no cylinders. I experienced a partially clogged injector in my M20F and it would run like shit when I'd hit 2300 RPM and wouldn't go past 2500RPM on the ground. Leaning the mixture out progressively would cause the #3 to run hot, but I could make full RPM. I of course did not takeoff until we fixed the issue. 

[carusoam]

Check one’s engine out restart procedures...

I think I recall, From initial training, the procedures including throttle sweeps and mixture sweeps and magneto sweeps....

There were various causes of partial engine failure that would be improved by altering the fuel / air ratio in a logical fashion...

Not bad, when you have time descending from the FLs... in training, it was do it once and then secure everything for an immediate landing...   

At least with an engine monitor, you have a hint of what isn’t working.  What you can do with that hint is up to you... is it one cylinder, or all four...?

PP thoughts only, not a cfi....

Best regards,

-a-

[cujet]

We operate an Experimental Exhibition Extra 300L, with a BPE AEIO540. The chief pilot experienced a near complete injector blockage after a takeoff and snap roll. He barely made it back, struggling along at about 150 feet. The engine was running horribly and he never thought to pull the mixture lever out a bit. Once on the ground, the Dynon Skyview was very helpful in troubleshooting. Here is what I noticed: Black smoke and very rough running at full power, no EGT on cyl 2 once power was increased. Although idle and some small amount of throttle was OK. However, at no point did the engine run like it had 5 healthy cylinders until a pull of the mixture lever to get EGT's high enough to get into the normal range.

I found a small piece of black rubber in the injector. 

Who knows if I as the pilot, would have tried to pull the mixture... However, this much I do know, it's good to try various things to troubleshoot a bad engine. Try each mag individually, try the fuel pump, try pulling the mixture, try moving the throttle, etc. Even as an A+P, I can't instantly diagnose an inflight problem, heck I'm probably way off base on my first guess. 

 

 

Edited June 12, 2018 by cujet

[kortopates]

27 minutes ago, cujet said:

We operate an Experimental Exhibition Extra 300L, with a BPE AEIO540. The chief pilot experienced a near complete injector blockage after a takeoff and snap roll. He barely made it back, struggling along at about 150 feet. The engine was running horribly and he never thought to pull the mixture lever out a bit. Once on the ground, the Dynon Skyview was very helpful in troubleshooting. Here is what I noticed: Black smoke and very rough running at full power, no EGT on cyl 2 once power was increased. Although idle and some small amount of throttle was OK. However, at no point did the engine run like it had 5 healthy cylinders until a pull of the mixture lever to get EGT's high enough to get into the normal range.

I found a small piece of black rubber in the injector. 

Who knows if I as the pilot, would have tried to pull the mixture... However, this much I do know, it's good to try various things to troubleshoot a bad engine. Try each mag individually, try the fuel pump, try pulling the mixture, try moving the throttle, etc. Even as an A+P, I can't instantly diagnose an inflight problem, heck I'm probably way off base on my first guess. 

A complete or near complete injector blockage has to be exceedingly rare. And I'd have to think if it would be far more likely to occur only after maintenance which included the injectors. After all, the screen in the fuel divider is going to capture anything large enough to fully block an injector - that's what its designed to do and should do. But it easy enough to introduce a large debris such a fragment from a cut o-ring gasket as the injector is re-installed which I assume is likely what happened here. Where else would it have come from that wouldn't have been caught by the fuel divider screen?  

I do appreciate you sharing your experience of a fully blocked injector and I assumed from Antares description it was in references to the typical partially blocked injector that I have seen the data for hundred's of times. Yet I haven't seen it all and always learning and can't recall ever seeing a fully blocked one in flight just appear. Yet I am also primed to check for this after maintenance and suggest how to do so at engine run-up. I've had to re-install an injector myself from nipping the o-ring on reinstall and causing a blockage issue.   

[N6018Q]

On ‎6‎/‎12‎/‎2018 at 12:53 PM, 1964-M20E said:

If the prop is still spinning the magnetos will still be firing assuming they were firing before the engine quit regardless if you have a turbo or not.  I'm not sure what trying to start the engine with the starter would have to do with that.  Now maybe the propeller will not windmill at higher altitudes I have not been that high to find out.  However, if I did have an engine failure and was trying a restart I'm going to let the prop windmill for that attempt and then if unsuccessful and have to put it down somewhere I'll try and stop the windmilling for greater glide if needed.

I have done a restart in the air already when I intentionally ran one tank dry on a long flight and yes I did lean the mixture before switching tanks so the engine would not over-speed when it started getting fuel again.

I'm gonna show my ignorance here- how do you stop the prop from spinning? I too noticed significant increase on the glide distance chart when the prop is stopped.

[FloridaMan]

2 hours ago, N6018Q said:

I'm gonna show my ignorance here- how do you stop the prop from spinning? I too noticed significant increase on the glide distance chart when the prop is stopped.

I’m getting old. 

 

Also, when attempting to make a target landing site, aim for the center of your imaginary (or real, if so lucky) runway. Only when you’re sure that you have it made, employ slips, etc to make your imagined approach end. 

[1964-M20E]

Thankfully I have never had to do this but if I am correct you pull the prop handle all the way out and I was told during initial training that if you slow the plane some past the best glide the pop will stop and then you can resume your glide.  I guess one could try this with enough altitude and near an airport actually stop the engine completely.

 

Maybe next time I find the need to use all fuel in one tank and if I am by myself I might try this.

[N6018Q]

Thanks, I appreciate the info

[smccray]

On 6/12/2018 at 2:46 PM, Antares said:

This needs to be discussed here. I'm ok with getting flamed for it, but one failure mode with a fully clogged injector can result in the other cylinders running too rich. The treatment is the same as for a turbocharger failure. Getting 3 cylinders back online is better than no cylinders. I experienced a partially clogged injector in my M20F and it would run like shit when I'd hit 2300 RPM and wouldn't go past 2500RPM on the ground. Leaning the mixture out progressively would cause the #3 to run hot, but I could make full RPM. I of course did not takeoff until we fixed the issue. 

A 4 cylinder engine has a bad reputation of running on 3 cylinders. I experienced a partial blockage years ago when pulling power back.  There was so much vibration I don’t think I could have maintained partial power.  Oddly, with the throttle all the way in she ran smooth and I was fine, and when I pulled power back to land the blockage resolved itself. 

Loosing a cylinder on a 6 cylinder engine has a reputation for roughness but the engine still running well enough to get back to an airport.

This feels like a subject for Byron.

[flyboy0681]

2 hours ago, smccray said:

A 4 cylinder engine has a bad reputation of running on 3 cylinders. I experienced a partial blockage years ago when pulling power back.  There was so much vibration I don’t think I could have maintained partial power.  Oddly, with the throttle all the way in she ran smooth and I was fine, and when I pulled power back to land the blockage resolved itself. 

 

Several years ago I was cruising along and experienced what we (me and A&P) believed to be a clogged injector. The plane shook really bad for about 30 seconds and smoothed out as I made a 180 back to the nearest airport, which was Tallahassee. It was a pretty hair raising situation.