How to Clean Injectors

[EricJ]

1 hour ago, MikeOH said:

So, what bad things happen if the bleed hole is improperly positioned?

They don't drain as well, and if the vent clogs up from dye goo they won't atomize fuel nearly as well.    They can also drain onto the outside of the nozzle and cylinder instead of into the intake, which just gets gunky and harder to clean.

That said, it's apparently not catastrophic to not position them "properly", as many people don't even know to do it, or just don't, or, like me, can't quite get them in the right spot, anyway.  I don't think I've heard too many sad stories of issues caused by misoriented nozzles, but things do seem to be a bit better if done properly.

[PT20J]

2 hours ago, MikeOH said:

So, what bad things happen if the bleed hole is improperly positioned?

A drop or two of fuel might drip out after shutdown and you could get some blue dye stains when it evaporates. Frankly, I’ve never worried about it. 

[MikeOH]

1 hour ago, PT20J said:

A drop or two of fuel might drip out after shutdown and you could get some blue dye stains when it evaporates. Frankly, I’ve never worried about it. 

Thank you!

I had taken the injectors out for cleaning not long ago and my A&P said the same, "don't sweat it" when I couldn't get the bleed holes properly aligned.  Then, at annual, the shop I used wanted a fortune to remove and clean injectors because of the blue stains!

I declined.  Then this thread showed up and I started to get concerned!

I'm back to "not worrying about it".

[Shadrach]

2 hours ago, MikeOH said:

Thank you!

I had taken the injectors out for cleaning not long ago and my A&P said the same, "don't sweat it" when I couldn't get the bleed holes properly aligned.  Then, at annual, the shop I used wanted a fortune to remove and clean injectors because of the blue stains!

I declined.  Then this thread showed up and I started to get concerned!

I'm back to "not worrying about it".

They stain no matter their position. I removed mine at last annual after many years and several hundred hours in service. They were all stained, but none of the vent screens had any blockages. 

[PT20J]

8 minutes ago, Shadrach said:

They stain no matter their position. I removed mine at last annual after many years and several hundred hours in service. They were all stained, but none of the vent screens had any blockages. 

That’s pretty much been my experience.

[spitzfyre]

I ended up tapping the holes, the tap had little resistance so that made me feel better about the condition of the threads. Upon install, I was able to get 3 of the 4 nozzles properly aligned, the 4th one would have required way over- or under-torque so I just left it. Ops and leak check went great. Thanks for the advice and info everyone

Edited September 5, 2023 by spitzfyre

[PT20J]

2 hours ago, spitzfyre said:

I ended up tapping the holes, the tap had little resistance so that made me feel better about the condition of the threads. Upon install, I was able to get 3 of the 4 nozzles properly aligned, the 4th one would have required way over- or under-torque so I just left it. Ops and leak check went great. Thanks for the advice and info everyone

Glad it worked. Next time though, it's safer to use a NPT thread chaser to clean up threads. 

[spitzfyre]

8 hours ago, PT20J said:

Glad it worked. Next time though, it's safer to use a NPT thread chaser to clean up threads. 

I did...... I have a tap/die kit that has the 1/8 npt tap that I needed

[Pinecone]

That point is, a thread chaser just cleans the threads.  It is less agressive than a tap.

 

 

 

[N201MKTurbo]

7 hours ago, Pinecone said:

That point is, a thread chaser just cleans the threads.  It is less agressive than a tap.

 

 

 

I've never seen an NPT thread chaser.

[A64Pilot]

21 hours ago, N201MKTurbo said:

I've never seen an NPT thread chaser.

I’ve not either, don’t understand how one could work on tapered threads 

[Bartman]

When my engine was installed the injectors would only go in about 2 threads and that just did not give a warm and fuzzy feeling.  I did most of the work with oversight and inspection and used the 1/8 inch pipe thread tap to clean the threads.  In order to minimize the chance of debris getting into the cylinder I did it very slowly and used a shop vac continuously. I paused the tapping efforts often to use the shop vac directly over the tap and spark plugs removed to allow for air flow.  Maybe it was overkill and not necessary, but this gave me some confidence that everything possible was done to prevent even the smallest amount of debris contamination. 

It took some time to do this methodically, but in the end we achieved optimal torque and proper alignment.

[blaine beaven]

Hi all,

Great thread, and kind of timely for me. I’ve been cleaning my injectors on a 300hr/every 3rd annual kind of schedule based on suggestion by my AME. 
 

Recently I was having some rough running issues and one of the things suggested was to clean the injectors. Given the amount of smoke and particulate in the air with all of the forest fires up here, it was suggested that could be clogging up the fuel injectors. 
 

The last time they were cleaned was 18 months and only 50 hours of flying prior. See the photos to see how dirty they looked. My AME said that they used their ultrasonic cleaner but we’re still getting some black soot out of them so took them to a local engine overhaul shop that had some better chemical cleaning material. 
 

I’m likely to now clean these annually for as long as we are having forest fires…

 

[Shadrach]

3 hours ago, blaine beaven said:

Hi all,

Great thread, and kind of timely for me. I’ve been cleaning my injectors on a 300hr/every 3rd annual kind of schedule based on suggestion by my AME. 
 

Recently I was having some rough running issues and one of the things suggested was to clean the injectors. Given the amount of smoke and particulate in the air with all of the forest fires up here, it was suggested that could be clogging up the fuel injectors. 
 

The last time they were cleaned was 18 months and only 50 hours of flying prior. See the photos to see how dirty they looked. My AME said that they used their ultrasonic cleaner but we’re still getting some black soot out of them so took them to a local engine overhaul shop that had some better chemical cleaning material. 
 

I’m likely to now clean these annually for as long as we are having forest fires…

 

Did it cure your rough running?  I have been on a 5 year 3/500hr schedule. I have never noticed a difference in functionality. The look stained upon removal but close inspection with magnification has never revealed any screen obstruction. The injector nozzles are spotless.

[A64Pilot]

2 minutes ago, Shadrach said:

Did it cure your rough running?  I have been on a 5 year 3/500hr schedule. I have never noticed a difference in functionality. The look stained upon removal but close inspection with magnification has not revealed any screen obstruction. The injector nozzles were spotless.

Assuming one has a good analyzer and to put it bluntly but knows what they are looking at, any issue with dirty injectors should highlight itself.

If you don’t have any change in when and in what order your cylinders peak, then it’s likely you don’t need to clean anything.

But if different cylinders start peaking first and or the spread between peaks is getting bigger then you may need to clean them.

In my opinion cleaning on a regular schedule is probably most applicable for people like me that don’t have an analyzer and won’t know somethings up until it won’t run LOP as smoothly as it used to, but then there is the argument that as long as it will, what’s to clean?

Two schools of thought, one guy cleans and rotates his plugs every oil change, next guy waits until Mag checks get flaky, Who’s right? Who’s wrong, both approaches work.

[Shadrach]

1 hour ago, A64Pilot said:

Assuming one has a good analyzer and to put it bluntly but knows what they are looking at, any issue with dirty injectors should highlight itself.

If you don’t have any change in when and in what order your cylinders peak, then it’s likely you don’t need to clean anything.

But if different cylinders start peaking first and or the spread between peaks is getting bigger then you may need to clean them.

In my opinion cleaning on a regular schedule is probably most applicable for people like me that don’t have an analyzer and won’t know somethings up until it won’t run LOP as smoothly as it used to, but then there is the argument that as long as it will, what’s to clean?

Two schools of thought, one guy cleans and rotates his plugs every oil change, next guy waits until Mag checks get flaky, Who’s right? Who’s wrong, both approaches work.

My engine is monitored. I have never seen evidence of a fuel delivery issue.  At last servo rebuild, I did ask the overhauler to set it as rich as spec would allow. That dropped my take off EGTs 60-100° into the high 1100s to low 1200s. Since then, I have seen all number of ignition issues, most of which were accurately diagnosed before shutdown. The fuel system soldiers on.
I cleaned the injectors last year mostly because I like a clean engine bay and 5 years and 300hs on they were becoming unsightly.

[DonMuncy]

I hate to act like a "know-it-all" and I admit that my knowledge has definite limits; but...

I know that injectors can get blocked by bits of junk. It happened to one of mine once. But I think that routine cleaning of injectors for a build-up of something is a waste of time. They get cleaned by a blast of solvent (av-gas) on every engine cycle. Has anyone ever seen a build-up in any injector bore?

 

[N201MKTurbo]

6 minutes ago, DonMuncy said:

I hate to act like a "know-it-all" and I admit that my knowledge has definite limits; but...

I know that injectors can get blocked by bits of junk. It happened to one of mine once. But I think that routine cleaning of injectors for a build-up of something is a waste of time. They get cleaned by a blast of solvent (av-gas) on every engine cycle. Has anyone ever seen a build-up in any injector bore?

 

Yes I have!

I had the same thoughts you have about 10 years ago. So I quit cleaning them at annual. After about 4 years in service my GAMI spread went to hell. I took out the injector orifices and took them to work and asked the machine shop manager to measure them. He gave me a box of gauge pins and told me to have fun. It turns out they are 0.028” bore. I could get a 0.028- pin (0.0278) through one of them some were down to 0.026. So I took the 0.028- pin and tapped it through the tightest one. It drove out  a perfect cylinder of clear varnish. So I tapped it through all the orifices. After that I was worried I may have damaged them, so I inspected the bores with an inspection microscope. I was able to focus down through the bores and clearly see the whole bore. There was no damage at all. FWIW, the bores appeared to be formed by an EDM sinker, not drilled.

 

After I put them back in the plane, my GAMI spread was perfect.

I would suggest just pulling the orifices and cleaning them ever year.

[kortopates]

10 minutes ago, DonMuncy said:

I hate to act like a "know-it-all" and I admit that my knowledge has definite limits; but...

I know that injectors can get blocked by bits of junk. It happened to one of mine once. But I think that routine cleaning of injectors for a build-up of something is a waste of time. They get cleaned by a blast of solvent (av-gas) on every engine cycle. Has anyone ever seen a build-up in any injector bore?

 

Exactly right. Not a week goes by that I don't see a partially clogged injector - diagnosed as such by becoming a lean outlier.

Everybody expects though that they'll be able to see the partial blockage with the naked eye. Its actually very seldom you can see the issue with the injector. When you can though, its usually a little piece of black o-ring on TCM injector - something you'll never see on a Lycoming. But most of the time you can't see a thing. And occasionally this has prevented someone from properly cleaning it in MEK and or Hoppes. My favorite is a Hoppes sonic bath followed by rinsing with MEK. Even though the clog can't be seen, a good cleaning always restores the full FF when there was a partial blockage.

But the simple act of R&R'ing the injectors is more likely to contaminate and injector than years in service so we never recommend servicing them just for the fun of it. A good fraction of the clogs we see are right after someone servicing them. Shop environments and mechanic's hands are pretty dirty and these require the utmost in cleanliness when handling them. 

 

[DonMuncy]

6 minutes ago, N201MKTurbo said:

Yes I have!

I had the same thoughts you have about 10 years ago. So I quit cleaning them at annual. After about 4 years in service my GAMI spread went to hell. I took out the injector orifices and took them to work and asked the machine shop manager to measure them. He gave me a box of gauge pins and told me to have fun. It turns out they are 0.028” bore. I could get a 0.028- pin (0.0278) through one of them some were down to 0.026. So I took the 0.028- pin and tapped it through the tightest one. It drove out  a perfect cylinder of clear varnish. So I tapped it through all the orifices. After that I was worried I may have damaged them, so I inspected the bores with an inspection microscope. I was able to focus down through the bores and clearly see the whole bore. There was no damage at all. FWIW, the bores appeared to be formed by an EDM sinker, not drilled.

 

After I put them back in the plane, my GAMI spread was perfect.

I would suggest just pulling the orifices and cleaning them ever year.

Thanks for the information. Do you (or anyone else) have an idea of what might have created that clear varnish build-up?

[N201MKTurbo]

7 minutes ago, DonMuncy said:

Thanks for the information. Do you (or anyone else) have an idea of what might have created that clear varnish build-up?

All I can think of is AVGAS.

When I was working on the Missile fueling system, they check the varnish (gum) levels before every fueling and once a day if they are not fueling. And that stuff is $75/gallon (JP10)

I think it comes from oxidation of the fuel. The storage tank for the JP10 was filled with nitrogen to limit oxidation.

[PT20J]

10 minutes ago, DonMuncy said:

Thanks for the information. Do you (or anyone else) have an idea of what might have created that clear varnish build-up?

Gasoline oxidizes when exposed to air and forms deposits. Remember back when cars had carburetors and we had to get the carburetor overhauled every so often? You would take it all apart and soak it in carburetor cleaner which would remove all the deposits. Because the deposits formed a yellowish coating on the aluminum parts, and because old fashioned wood varnishes yellowed with age, people got to calling these deposits varnish. 

When auto makers ditched carburetors for fuel injection, there were problems with injectors clogging and automakers lobbied the EPA to mandate minimum detergent standards for auto gas. 

I don't know what if any detergent is in avgas, but I'm pretty sure it is way less than auto gas.

Skip

[PT20J]

If you want to minimize the chance of contamination, you can follow the RSA manual and just clean the restrictors.

[EricJ]

In addition to varnish in the nozzle restrictor bores, the condition of the vent makes a difference in how well the fuel atomizes.    At least, that's what it's there for.    The vents can get clogged by varnish or evaporated dye goo or even the forest fire dirt or dust or other crap that's in the air.

If you clean them using the process in Lycoming SI 1275C, one of the solvents that is recommended is Hoppes No. 9, so that's what I use, partly because it is a bit less harsh than some of the other solvents (e.g., MEK).   I put a little in a small container barely bigger than the nozzle and let it soak for the recommended time, and usually the Hoppes solvent will end darker and ickier than it started, so it's removing *something*.   My nozzles don't typically look filthy going in, but they leave enough crap in the Hoppes that I dump it and use a clean batch for the next nozzle.

[A64Pilot]

1 hour ago, DonMuncy said:

I hate to act like a "know-it-all" and I admit that my knowledge has definite limits; but...

I know that injectors can get blocked by bits of junk. It happened to one of mine once. But I think that routine cleaning of injectors for a build-up of something is a waste of time. They get cleaned by a blast of solvent (av-gas) on every engine cycle. Has anyone ever seen a build-up in any injector bore?

 

An injector is not just a carburetor jet, to continue the carburetor comparison it’s an emulsion tube. That is it mixes air and fuel, the air bleed isn’t flushed by 100LL and yes it can clog, it’s a screen presumably to stop from sucking in bits of dirt to clog the air bleed hole, so the screen is a filter and like all filters it can and will over time become blocked