Jump to content

Clogged Injectors


MV Aviation

Recommended Posts

Hi everybody,

I own a M20E, which has a fuel injected IO-360, with which I've recently experienced some recurring issues.

It all started with an engine start on a relatively cold day (sub freezing). Not sure if that has something to do with the issue, but I mention it for completeness. Anyway, engine start and run-up went well. I took off and shortly after takeoff in about 300-400ft AGL experienced some extreme engine roughness. I immediately pitched down, pushed the mixture full forward, engaged the electrical fuel pump and after a few seconds with no changes in the symptoms, decided to return immediately. On my EDM830 engine monitor I noticed that cylinder no 2 wasn't making any power. You can see that on the graph below. The orange line is C2 EGT, while the green one shows C2 CHT. EGT drops almost instantly, CHT follows slowly due to the thermal mass of the cylinder itself.

After landing I did a couple of checks (extended run-ups, played with the mixture, etc.) and still saw that C2 wasn't working correctly, although it came back and made some power. The higher ETG suggests that C2 was getting less fuel than the other cylinders, therefore, during hotter. My first guess was that some water may have frozen in the fuel line leading to C2, which is exposed to the cold environment on takeoff. However, since the problem continued on the ground, with a warmed up engine from the take off and no air speed, I dismissed that theory. Long story short, I eventually unscrewed the C2 fuel line from the injector and found it to be clogged with a particle similar to the photo below. I cleaned the nozzle in acetone, like a Lycoming SB recommends. After putting everything together, the engine worked normally again. 

Some uneventful flights later, I experienced a similar behavior (this time on a warmer day) but on cylinder number 4. The engine wasn't shaking violently, like the first time, but the issue was observable on the EDM. I normally fly LOP in cruise, but with C4 reaching peak about 200°F earlier than all other cylinders, LOP was no option. Flushing with the mixture didn't help. Again, I opened up the injector on C4 and found it to be partially clogged (attached picture). This time I kept the particle and checked whether it was magnetizable, which it was not. Hence, at least I know its not a variant of steel.

Overall it seems like some component in the fuel system is, from time to time, loosing particles with a size that is able to clog the injectors. Does anyone have experience with anything like that? Could it be the inside of a fuel hose that is dissolving? Btw. draining the tanks never revealed any significant debris in the tanks and factory new bladders were installed only 1.5 years ago.

Happy landings!

Marco

image.thumb.png.36a3b959b46d2f6fd493309aab74d9e7.png

IMG_8405.thumb.jpg.d33de7c155126c60d019a5d821f220cd.jpg

 

  • Like 1
Link to comment
Share on other sites

I would inspect the finger screen in the servo for debris. I would remove and flush the hose from the servo to the divider. I would pull the plunger out of the divider and inspect for any debris in there. Blow out all the injector lines to make sure nothing is in there.

The finger screen is supposed to stop anything that could clog the injectors, but the orifice is only 0.028”. A particle that size can obviously sneak through.

  • Like 2
Link to comment
Share on other sites

When I first bought my airplane I had similar issues, with multiple clogging events.   The first thing I'd recommend is to check the finger filter screen inside the fuel servo.   Remove it from the feed (supply line) side so that it doesn't trail any captive debris into the fuel servo.   This is the last filter before the injectors, and if there's a lot of crap that's getting to the injectors it's going to accumulate there first.   In my case it was full of a lot of rusty debris.   If there's a lot of stuff in the finger filter, check the screen at the electric boost pump if you have one.

FWIW, the presence of the rusty junk in my servo screen may have been an indicator for a subsequent fuel servo failure that happened.   It's probably a good idea to check things soon.

 

  • Like 2
Link to comment
Share on other sites

5 minutes ago, N201MKTurbo said:

I would inspect the finger screen in the servo for debris. I would remove and flush the hose from the servo to the divider. I would pull the plunger out of the divider and inspect for any debris in there. Blow out all the injector lines to make sure nothing is in there.

The finger screen is supposed to stop anything that could clog the injectors, but the orifice is only 0.028”. A particle that size can obviously sneak through.

The finger screen isn’t that small. I’ve had a number of things make it past. Biggest culprit is after tank reseal if not using a top coat. 

Link to comment
Share on other sites

Great aviating MV!

Fantastic troubleshooting!

 

See if you can determine what it is...

See if there is more of it on the finger screen...

See if you can tell if it is part of the rubber liner from the fuel line that feeds the fuel injection system...

 

Often, a degraded fuel hose starts losing its surface layer... and sends the bits toward the fuel injectors...

PP thoughts only, stuff I have only read about around here...

Best regards,

-a-

  • Like 1
Link to comment
Share on other sites

23 minutes ago, carusoam said:

Great aviating MV!

Fantastic troubleshooting!

 

See if you can determine what it is...

See if there is more of it on the finger screen...

See if you can tell if it is part of the rubber liner from the fuel line that feeds the fuel injection system...

 

Often, a degraded fuel hose starts losing its surface layer... and sends the bits toward the fuel injectors...

PP thoughts only, stuff I have only read about around here...

Best regards,

-a-

That happened to me after my plane sit for a couple years after an inflight engine failure. I had other planes to fly and took my time. When I got it running again I kept getting plugged injectors from the fuel lines having sat. Eventually replaced all the rubber lines in the plane. 

  • Like 1
Link to comment
Share on other sites

Had a C-210 that did it regularly enough that I flew with a can of carb cleaner and wrench and deep well socket.

‘The can of carb cleaner with the straw works really well, just be darned sure none sprays back into your eye, you’ll only let that happen once.

‘Ended up being a fuel hose coming apart, pull screens and if you find what looks like little black granules I bet that’s it.

  • Like 1
Link to comment
Share on other sites

11 minutes ago, RobertGary1 said:

In my experiences it’s rarely necessary to remove the injector. Just pull the insert out and blow on it. Don’t lose them. They are not sold without the full injector. 

Except that not all injectors are the two piece type.  Lots of older one piece style are still in service.

Clarence

Link to comment
Share on other sites

I've been fighting this problem for months.  After (your A&P is done) cleaning the nozzles and the ports they go into, (the A&P should) check the fuel bowl (bottom of selector; be careful putting the o-ring back on), inline filter (just forward of fuel pump; from a SB, you may not have it), and finger screen (behind fuel inlet on fuel servo) for debris.  Check inside the finger screen chamber to make sure it isn't full (mine was so full of rust and "gunk" that the finger screen wouldn't come out without a pretty good tug).  Check the age of the fuel lines, if 5-7 years or older, they probably should be replaced.

I'm told flushing the fuel divider's hard lines with a couple gallons of fuel every annual can make a difference on the -A1A engines, so you might try that (I have not at this point; didn't know about it until pretty recently).

Another possibility: Are your fuel tanks leaking due to failing sealant?  That seems to have been the cause of my problems (much to my pocketbook's chagrin).

Link to comment
Share on other sites

1 hour ago, afward said:

I've been fighting this problem for months.  After (your A&P is done) cleaning the nozzles and the ports they go into, (the A&P should) check the fuel bowl (bottom of selector; be careful putting the o-ring back on), inline filter (just forward of fuel pump; from a SB, you may not have it), and finger screen (behind fuel inlet on fuel servo) for debris.  Check inside the finger screen chamber to make sure it isn't full (mine was so full of rust and "gunk" that the finger screen wouldn't come out without a pretty good tug).  Check the age of the fuel lines, if 5-7 years or older, they probably should be replaced.

I'm told flushing the fuel divider's hard lines with a couple gallons of fuel every annual can make a difference on the -A1A engines, so you might try that (I have not at this point; didn't know about it until pretty recently).

Another possibility: Are your fuel tanks leaking due to failing sealant?  That seems to have been the cause of my problems (much to my pocketbook's chagrin).

The gas collator should be inspected at every annual. 

  • Like 1
Link to comment
Share on other sites

Last month I had this happen to my plane except it was the number 4 cylinder and it happened on the ground so I did not go airborne.  Turned out a small piece of dirt got into the spider valve.  After it was cleaned out, no more problem.

Link to comment
Share on other sites

Thanks for all your reports. I will have a look at the screen next. I haven't had any problems like that in the past 4.5 years I owned the Mooney. And, as said, the bladders were freshly installed 1.5 years ago, so sealant cannot be the source of the issue.

This incident taught me that a digital engine monitor is worth a lot. Troubleshooting would not have been as straight forward as it was without it. Also, watch EGTs during run-up! Although temps are not close to peak at 1700rpm and full rich, some issues can be identified while still on the ground.

  • Like 2
Link to comment
Share on other sites

First time it happened to me on the 210, I went full rich and boost on to try to keep temps on that cyl down.

After the first time of doing all of that I didn’t richen up, boost etc, just let that cylinder lean out and die,of course it cooled way off then, and I wasn’t slobbering the others with fuel. Seems to be a better way of dealing with it.

‘Of course that was a 6 cyl, but I believe even a four will run OK smooth on three

 A handheld IR thermometer will find the bad cylinder instantly for those that may not have an engine monitor, even your hand usually will.

‘Monitors are nice to have, it’s maybe my next purchase, I’ll go with the UBG-16 because the owner is a friend.

Edited by A64Pilot
Link to comment
Share on other sites

45 minutes ago, A64Pilot said:

First time it happened to me on the 210, I went full rich and boost on to try to keep temps on that cyl down.

After the first time of doing all of that I didn’t richen up, boost etc, just let that cylinder lean out and die,of course it cooled way off then, and I wasn’t slobbering the others with fuel. Seems to be a better way of dealing with it.

‘Of course that was a 6 cyl, but I believe even a four will run OK smooth on three

 A handheld IR thermometer will find the bad cylinder instantly for those that may not have an engine monitor, even your hand usually will.

‘Monitors are nice to have, it’s maybe my next purchase, I’ll go with the UBG-16 because the owner is a friend.

Ive heard it said that today the faa probably wouldn’t approve injected engines without multi prob egt sensors. Speculation of course since Lycomjng got their approval generations ago. But I can say it’s kept me from burning up my new engine from Lycoming. One cylinder egt was running 200F hotter than the rest.  Found goop in the injector. 

Link to comment
Share on other sites

41 minutes ago, A64Pilot said:

‘Of course that was a 6 cyl, but I believe even a four will run OK smooth on three

A 4 cyl engine will definitely not run smoothly on three cylinders, not even on 3.5 cylinders. On the last flight with a partially clogged injector, I managed to go approx. 50°F LOP on the faulty cylinder and about 100°F ROP on all other cylinders. That was sustainable in cruise, otherwise I would have aborted the flight. Going any leaner introduced vibrations on the clogged cylinder and "shutting it off" by going even leaner, would not have been pleasant at all.

On a 6 cyl engine on the other hand, I can imagine running wit only 5 is ok.

Link to comment
Share on other sites

I can corroborate this: Having a single cylinder not producing close to the same power as the rest is a very uncomfortable experience with a Lycoming IO-360.

In my case, I could run about 75% power with a full rich mixture and get a smooth-running engine.  That put the lean cylinder right at the bottom of the red fin (safe, but barely) and the rest well above the top.  Pulling back to land was not pleasant, though.  Very rough running.

6 cylinder engines do have the benefit of having overlapping power strokes.  That makes them far more smooth just in general, so losing a cylinder really just makes one feel like an average 4 cylinder aero engine. :)

Link to comment
Share on other sites

I’m not saying it will be smooth or to continue flight, just that it will probably run without tearing any mounts up.

‘A 6 running on five isn’t smooth either, has you pushing the nearest button on the GPS, even my C-85 will run on three, but not smoothly, I had a bad plug and on one mag it was only on three is how I know.

‘But engines are different, blow a jug off of a 985 and it will continue to run, blow a jug on a 1340 and it won’t, so saying a C-85 will run on three doesn’t meant that a Lycoming 360 will, but I believe it will. They will run with a stuck valve or broken rings, just not well.

‘Of course you handle it however you want,  just in the C-210 with its IO-520, making it run slobbering rich meant high manifold pressure to maintain level flight, couple that with the lean cylinder running excessively high EGT. After thought it was better to just let the clogged one lean out and quit, but if you don’t like that, push the red knob back in and or turn on the boost pump.

‘On our Lycomings I don’t think turning on the boost richens up the mixture like high boost on an IO-520 anyway, so all you can do is go full rich, the big Continental with high boost, you can make it slobbering rich, like a car with the choke on, so I guess that the difference.

I guess the takeaway is if a plugged injector puts a cylinder near peak EGT, be careful of high manifold pressures is all, and if you can’t avoid high manifold pressures and it looks like it may be headed for detonation, let it go so lean that it can’t detonate is a way to deal with a plugged injector.

Link to comment
Share on other sites

Back many years ago, I put too much anti seize on my plugs and fouled both plugs on one cylinder. I flew 20 miles back to the airport on 3 cylinders. It was rough, but it kept going. I throttled back to enough power to keep me in the air, about 65 KTS. the lower the power the smoother it was. 

Link to comment
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.