Fuel injectors cleaning

[Shadrach]

We decided to pull and clean the injectors this year after many years and a little over 500hrs in service.  While the nozzles were all clear and free from residue, the screens and shields were stained dark blue from fuel residue. I cannot say whether fuel atomization was hindered by the stains on the screens. The staining was significant enough to warrant light brushing (soft bristle toothbrush) after soaking overnight in Hoppes #9. I have not flown it yet so can’t speak to changes in EGT. My take is that servicing on time in service is a good idea. Servicing on calendar time every year is overkill. 

 

[M20F]

“The next item that caught my eye was a $200 estimate for cleaning the engine’s fuel injector nozzles. I used to do such prophylactic nozzle cleaning on my own airplane until about 10 years ago, when I had an illuminating discussion with George Braly (of GAMI and Tornado Alley Turbo fame), who is arguably the world’s expert on fuel nozzles. George pointed out to me that there’s no valid reason to do such periodic nozzle cleaning, because the nozzles do not get dirty in service (since they are continuously being cleaned by a very effective solvent). He told me that in his experience with many thousands of GAMIjector nozzles, virtually all clogged nozzle events occurred shortly after maintenance during which the fuel system was opened up and some foreign material got into the system. That resonated with me, because in the first 12 years I owned my Cessna T310R, I experienced two clogged-nozzle episodes, and both occurred right after maintenance due to grease getting into the fuel system. So I stopped cleaning my nozzles 10 years ago, and haven’t had a clogged nozzle since.” - Mike Busch

[Shadrach]

12 minutes ago, M20F said:

“The next item that caught my eye was a $200 estimate for cleaning the engine’s fuel injector nozzles. I used to do such prophylactic nozzle cleaning on my own airplane until about 10 years ago, when I had an illuminating discussion with George Braly (of GAMI and Tornado Alley Turbo fame), who is arguably the world’s expert on fuel nozzles. George pointed out to me that there’s no valid reason to do such periodic nozzle cleaning, because the nozzles do not get dirty in service (since they are continuously being cleaned by a very effective solvent). He told me that in his experience with many thousands of GAMIjector nozzles, virtually all clogged nozzle events occurred shortly after maintenance during which the fuel system was opened up and some foreign material got into the system. That resonated with me, because in the first 12 years I owned my Cessna T310R, I experienced two clogged-nozzle episodes, and both occurred right after maintenance due to grease getting into the fuel system. So I stopped cleaning my nozzles 10 years ago, and haven’t had a clogged nozzle since.” - Mike Busch

Indeed one of George’s colleagues said as much to me many years ago which influenced my thinking on the subject. That being said, the screens were pretty stained. In looking at the pictures, they do not appear at all blocked so the cleaning could be purely cosmetic. I can’t say for sure. Not expecting a difference in how it runs but we’ll see.

[PT20J]

Careful about soaking too long in Hoppes #9. It’s good for dissolving lead, but it also etches brass. MEK is safer if you need a long soak.

I had a nozzle clog at about 325 hrs. I fly a lot of short flights. I think that every time you shut down, the hot engine boils the fuel out of the lines and leaves deposits behind. So, now I’m cleaning them every other year. 

Lycoming and AvStar say to remove the entire injector and soak it. Precision Airmotive says you only need to remove and soak the restrictor insert and blow the body out with air.  

Common mistake is over-tightening the nut on the fuel line which will crack.

Skip

[Shadrach]

27 minutes ago, PT20J said:

Careful about soaking too long in Hoppes #9. It’s good for dissolving lead, but it also etches brass. MEK is safer if you need a long soak.

I had a nozzle clog at about 325 hrs. I fly a lot of short flights. I think that every time you shut down, the hot engine boils the fuel out of the lines and leaves deposits behind. So, now I’m cleaning them every other year. 

Lycoming and AvStar say to remove the entire injector and soak it. Precision Airmotive says you only need to remove and soak the restrictor insert and blow the body out with air.  

Common mistake is over-tightening the nut on the fuel line which will crack.

Skip

No visible etching after an over night (~12hrs). We finished with a quick MEK soak and then blew them out. The Hoppes label warned about etching nickel but not brass.  If it eats brass that could be a problem as most firearm cleaning  rods, brushes and jags are made of brass.

overtighteneing B nuts will crack the injector flange. I still have four cracked injectors that I removed from the plane about 15 years ago.

[PT20J]

40 minutes ago, Shadrach said:

No visible etching after an over night (~12hrs). We finished with a quick MEK soak and then blew them out. The Hoppes label warned about etching nickel but not brass.  If it eats brass that could be a problem as most firearm cleaning  rods, brushes and jags are made of brass.

overtighteneing B nuts will crack the injector flange. I still have four cracked injectors that I removed from the plane about 15 years ago.

When I took the Lycoming factory class, one of the attendees was an A&P and mentioned that she left injectors soaking in Hoppes over a weekend and they were junk on Monday. The instructor pointed out that Lycoming SI 1275 says to soak in Hoppes for only 20 min.

But, I’ve never tried it. You could take one of your old injectors and run a test and let us know 

Skip

[Shadrach]

17 minutes ago, PT20J said:

When I took the Lycoming factory class, one of the attendees was an A&P and mentioned that she left injectors soaking in Hoppes over a weekend and they were junk on Monday. The instructor pointed out that Lycoming SI 1275 says to soak in Hoppes for only 20 min.

But, I’ve never tried it. You could take one of your old injectors and run a test and let us know 

Skip

I’m up for that. Far less disgusting than a lantern fly in avgas. FYI, no bug parts in gascolator screen this year. Maybe next year.

[kortopates]

If you have an engine monitor with fuel flow, and know how to measure your mixture distribution doing so on a regular basis will always keep you informed as to when an injector needs cleaning and which one(s). I no longer clean all at once because there is too good a chance dirt will get into the system when an injector is re-installed. It's not necessarily dirt either but can be a piece of a nicked o-ring. It happens much more than you think after prophylactic cleaning. It takes so little that it's common you can't see the debris in injector with the naked eye - but cleaning resolves the issue when it really needs it.


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[Guest]

Once again I’ll be the outlier, the only time I’ve had injector issues after clearing was when the nozzles weren’t rinsed with MEK and blown dry. The Hopps dried in the nozzle creating a complete blockage.  If you rinse your 1/2” socket in Hopps and treat it as though it were an extra nozzle you won’t introduce any dirt.

[A64Pilot]

I’m wondering where there is an O-ring?

I put them in baby food jars with Hoppes and ultrasonic them for 15 min or so. Keep the baby food jars, the Hoppes will be good for many years.

The only clogs I’ve had were sudden, black particles coming from I believe a deteriorating fuel hose. But you know theses things are atomizers aren’t they, that is they pull air through the screens to mix with the fuel, dirty screens cut down with atomization, it’s not just a fuel nozzle.

Turbine injectors and Diesel injectors are spray checked to validate atomization, that’s not done with piston engine injectors, so they may flow perfectly because the fuel isn’t restricted, but won’t atomize properly because the screens are dirty blocking the air flow.

Why do people not want to follow the manufacturers maintenance schedule?

[Shadrach]

On 10/24/2022 at 9:55 PM, PT20J said:

When I took the Lycoming factory class, one of the attendees was an A&P and mentioned that she left injectors soaking in Hoppes over a weekend and they were junk on Monday. The instructor pointed out that Lycoming SI 1275 says to soak in Hoppes for only 20 min.

But, I’ve never tried it. You could take one of your old injectors and run a test and let us know 

Skip

One on the left soaked for 5 days. One on the right for 20 mins. No visible etching on either to my eye. The orifices appear identical but I don’t have a micrometer that small.
 The one on the left is certainly a bit cleaner.

[PT20J]

1 hour ago, Shadrach said:

One on the left soaked for 5 days. One on the right for 20 mins. No visible etching on either to my eye. The orifices appear identical but I don’t have a micrometer that small.
 The one on the left is certainly a bit cleaner.

Thanks, Ross. Nothing beats a real test!

Skip

[skykrawler]

Yearly I used MEK overnight until I ordered a bottle of Hoppes.   I had lightly scratched cylinder #s on one of the flats and to help determine the correct position of the orifice.   Left them soak in the Hoppes overnight.....and the cylinder #s were gone.   So I won't do that again.

Also, I used a Q-tip on the inside of the barrel and discovered a fair amount of crud even after having soaked them.

I agree that hours in service is better than annually.

[A64Pilot]

I don’t think it etches it so much as removes the lead out of it, which I guess could cause etching. brass has significant amount of lead in it and Hoppes is specifically formulated to remove lead fouling from guns, or so it claims.

Just as an example if you have stray current on a boat, it will very likely “de-zincify” your bronze prop, at first it takes on a pinkish color and if not fixed eventually eats the prop up. But at first other than the color change there is no evidence of the zinc being leeched out.

Lycoming recommends 20 min for a reason, I can’t be sure why, but why wouldn’t anyone follow the manufacturers directions?

I put them in babyfood jars and ultrasonic them for 15 min or so myself.

 

[DCarlton]

On 10/25/2022 at 2:53 PM, A64Pilot said:

I’m wondering where there is an O-ring?

I put them in baby food jars with Hoppes and ultrasonic them for 15 min or so. Keep the baby food jars, the Hoppes will be good for many years.

The only clogs I’ve had were sudden, black particles coming from I believe a deteriorating fuel hose. But you know theses things are atomizers aren’t they, that is they pull air through the screens to mix with the fuel, dirty screens cut down with atomization, it’s not just a fuel nozzle.

Turbine injectors and Diesel injectors are spray checked to validate atomization, that’s not done with piston engine injectors, so they may flow perfectly because the fuel isn’t restricted, but won’t atomize properly because the screens are dirty blocking the air flow.

Why do people not want to follow the manufacturers maintenance schedule?

Why?  I'm not a professional mechanic but watching someone wrench on those small nuts and manipulating those small fuel lines during every annual or every 100 hours "scares" me.  My concern is the potential for maintenance induced failures when cleaning something that shows no sign of needing to be cleaned.   Or having to use helicoils to repair a perfectly good cylinder because threads were stripped.  

[A64Pilot]

You need a better mechanic then. 

So you don’t clean plugs either until they foul? Whole lot more risk of damage with a steel plug than a brass injector damaging threads, but if you use plain simple mechanic sense and start everything by fingers there won’t be any damage, only damage I’ve seen was on things that hadn’t been removed in a long time and the carbon build up is so much it backs out the helicoil with the plug. Anti seize and regular removal stops that. I’ve never myself seen a plug or nozzle cross threaded myself, but given enough time anything that can happen eventually does, so I’m sure it’s happened.

The only real damage I’ve really seen was ignoring the fuel lines, that leads to an engine out and possibly a bad fire, there is of course an AD to not ignore the lines, oh and ignoring mags until they fall off, from what I’ve seen not checking things causes more damage. Add ignoring exhausts to that list too, seen fires from that.

As I said these things are atomizers, that means they mix fuel with air so you get a spray, not a stream, it’s not just a fuel nozzle, you need to keep the screens clean too if you want them to work properly.

These are Certified aircraft, you don’t get to chose which inspections you think are necessary, if that’s what you want, build an Experimental, then you can choose to ignore the engine manufacturer who clearly doesn’t know anything and you don’t have to let that dummy A&P touch your machine either.

There are some very capable Experimental’s now, they aren’t just VW powered rag wings like back when.

Oh, and I have been a Professional Mechanic since 1988, but only really made my living being one from 1982 to 1987, from the. on I made my living as a Pilot.

For goodness sake people, follow the manufacturers recommendations, these things have been around for a very long time, if they were wrong don’t you think they would have been changed by now?

You want to lose sleep over something, lose it over the Cam that for no apparent reason sometimes decides to eat itself

[DCarlton]

17 minutes ago, A64Pilot said:

You need a better mechanic then. 

So you don’t clean plugs either until they foul? Whole lot more risk of damage with a steel plug than a brass injector damaging threads, but if you use plain simple mechanic sense and start everything by fingers there won’t be any damage, only damage I’ve seen was on things that hadn’t been removed in a long time and the carbon build up is so much it backs out the helicoil with the plug. Anti seize and regular removal stops that. I’ve never myself seen a plug or nozzle cross threaded myself, but given enough time anything that can happen eventually does, so I’m sure it’s happened.

The only real damage I’ve really seen was ignoring the fuel lines, that leads to an engine out and possibly a bad fire, there is of course an AD to not ignore the lines

As I said these things are atomizers, that means they mix fuel with air so you get a spray, not a stream, it’s not just a fuel nozzle, you need to keep the screens clean too if you want them to work properly.

These are Certified aircraft, you don’t get to chose which inspections you think are necessary, if that’s what you want, build an Experimental, then you can choose to ignore the engine manufacturer who clearly doesn’t know anything and you don’t have to let that dummy A&P touch your machine either.

There are some very capable Experimental’s now, they aren’t just VW powered rag wings like back when.

Oh, and I have been a Professional Mechanic since 1988, but only really made my living being one from 1982 to 1987, from the. on I made my living as a Pilot.

For goodness sake people, follow the manufacturers recommendations, these things have been around for a very long time, if they were wrong don’t you think they would have been changed by now?

You want to lose sleep over something, lose it over the Cam that for no apparent reason sometimes decides to eat itself

Understand your points.  There was another long thread on this a while back with both viewpoints expressed.  Plenty of votes on both sides.  I could be wrong but I do believe you get to choose in this case.  I recall several manufacturer recommendations and I recall recommendations regarding 100 hour inspections or annuals but I don't recall any FAA mandated requirements.  The last time this was debated, I concluded by saying that if my mechanic said they didn't need to be cleaned every annual I would be fine.  I also said that if my mechanic said they needed to be cleaned IAW their shops policies or standard operating procedures based on manufacturer recommendations I would be fine.  I rarely fly a 100 hours a year, so my personal choice would be to wait 2-3 years between cleaning cycles if there's no sign of an issue on an engine monitor. 

[A64Pilot]

I’m not a Lawyer, (my parents were Married, to each other) apology to those that are, just couldn’t resist    but if it’s in the Annual checklist you use, then you have to perform those inspections. I can’t come up with any logical reason to not use Mooney’s, as a buyer I want to see the Mooney list was followed, I may increase scope and or frequency of an inspection if I had unusual operating conditions, like air filter if I flew off of dusty dirt fields for example, but I’m not skipping one.

Now a Mechanic is allowed to come up with their own list, but in my opinion if a manufacturer publishes one, it’s tough to defend why you as a mechanic didn’t use it when being questioned by an FAA inspector, and my assumption is the owner wants the Annual performed IAW the manufacturers recommendations too.

I believe Mooney follows the engine manufacturer and says clean them. Then of course Lycoming says clean them, so as both say so, I do.

Look at it this way, God forbid an aircraft I worked on went down, and of course it’s very likely I’ll get a visit from an FAA inspector and should, it’s tough to justify as a mechanic why you chose to ignore inspections listed in both the airframe and engine manufacturers manuals. If I were the inspector I’d immediately wonder what other corners were cut and start looking.

Besides I have to look at myself every morning in the mirror, I don’t want to be thinking that maybe I shouldn’t have skipped those inspections. By not doing manufacturer's inspections you are in effect saying you know better than them, and that’s a tough one to defend 

 

[M20F]

1 hour ago, A64Pilot said:

For goodness sake people, follow the manufacturers recommendations, these things have been around for a very long time, if they were wrong don’t you think they would have been changed by now?

Back to ROP it is, at least we won’t have to debate it anymore….

[Shadrach]

1 hour ago, A64Pilot said:

I’m not a Lawyer, (my parents were Married, to each other) apology to those that are, just couldn’t resist    but if it’s in the Annual checklist you use, then you have to perform those inspections. I can’t come up with any logical reason to not use Mooney’s, as a buyer I want to see the Mooney list was followed, I may increase scope and or frequency of an inspection if I had unusual operating conditions, like air filter if I flew off of dusty dirt fields for example, but I’m not skipping one.

Now a Mechanic is allowed to come up with their own list, but in my opinion if a manufacturer publishes one, it’s tough to defend why you as a mechanic didn’t use it when being questioned by an FAA inspector, and my assumption is the owner wants the Annual performed IAW the manufacturers recommendations too.

I believe Mooney follows the engine manufacturer and says clean them. Then of course Lycoming says clean them, so as both say so, I do.

Look at it this way, God forbid an aircraft I worked on went down, and of course it’s very likely I’ll get a visit from an FAA inspector and should, it’s tough to justify as a mechanic why you chose to ignore inspections listed in both the airframe and engine manufacturers manuals. If I were the inspector I’d immediately wonder what other corners were cut and start looking.

Besides I have to look at myself every morning in the mirror, I don’t want to be thinking that maybe I shouldn’t have skipped those inspections. By not doing manufacturer's inspections you are in effect saying you know better than them, and that’s a tough one to defend 

 

The injectors used in my Hoppes experiment were removed from my aircraft ~15 years ago because they were cracked do to being over torqued (cracks are visible in pics). Given the talk of multi day exposure to Hoppes ruining injectors, I thought it would be interesting to see. What else am I going to do with unairworthy injectors? 
 

As a Mechanic, how many hours would you let a recip fly in between annuals before pulling injectors for cleaning? 150? 250?   1000? or just annually regardless of time in service?   
 

What about wheel bearings? They’re on the list. Should they be repacked annually regardless of usage?

I would be more concerned about the fuel system on a day to day basis if the only in service indication of proper function I had was a single cylinder analogue gage.  

[Will.iam]

4 minutes ago, Shadrach said:

The injectors used in my Hoppes experiment were removed from my aircraft ~15 years ago because they were cracked do to being over torqued (cracks are visible in pics). Given the talk of multi day exposure to Hoppes ruining injectors, I thought it would be interesting to see. What else am I going to do with unairworthy injectors? 
 

As a Mechanic, how many hours would you let a recip fly in between annuals before pulling injectors for cleaning? 150? 250?   1000? or just annually regardless of time in service?   
 

What about wheel bearings? They’re on the list. Should they be repacked annually regardless of usage?

I would be more concerned about the fuel system on a day to day basis if the only in service indication of proper function I had was a single cylinder analogue gage.  

That is a very valid and interesting point. When mooney specified yearly injector cleanings and flying 50 ROP of peak they did not have the instrumentation and test knowledge we have today. Would they still recommend the same interval cleaning and ROP flying?  

[N201MKTurbo]

I found the only way to accurately measure the orifice is with gauge pins or an optical comparator. I used both and mine were 0.028 +- 0.0001

I inspected mine by focusing a microscope down the bore of the orifice. The finish was amazing, not even a hint of a tool mark. I suspect the holes were finished with an EDM sinker.

[DCarlton]

57 minutes ago, Shadrach said:

The injectors used in my Hoppes experiment were removed from my aircraft ~15 years ago because they were cracked do to being over torqued (cracks are visible in pics). Given the talk of multi day exposure to Hoppes ruining injectors, I thought it would be interesting to see. What else am I going to do with unairworthy injectors? 
 

As a Mechanic, how many hours would you let a recip fly in between annuals before pulling injectors for cleaning? 150? 250?   1000? or just annually regardless of time in service?   
 

What about wheel bearings? They’re on the list. Should they be repacked annually regardless of usage?

I would be more concerned about the fuel system on a day to day basis if the only in service indication of proper function I had was a single cylinder analogue gage.  

I shake my head every year when we remove wheels and repack wheel bearings every 12 months... again.  There's gotta be a better place to put the time and money if you know your own airplane, usage and operating environment well enough.  But I'm no expert...  just an engineer and pilot with a personal opinion.  And with wheel bearings I really don't worry about maintenance induced failures, just wasted time and money.  

[A64Pilot]

1 hour ago, Shadrach said:

The injectors used in my Hoppes experiment were removed from my aircraft ~15 years ago because they were cracked do to being over torqued (cracks are visible in pics). Given the talk of multi day exposure to Hoppes ruining injectors, I thought it would be interesting to see. What else am I going to do with unairworthy injectors? 
 

As a Mechanic, how many hours would you let a recip fly in between annuals before pulling injectors for cleaning? 150? 250?   1000? or just annually regardless of time in service?   
 

What about wheel bearings? They’re on the list. Should they be repacked annually regardless of usage?

I would be more concerned about the fuel system on a day to day basis if the only in service indication of proper function I had was a single cylinder analogue gage.  

You follow the checklist, if Mooney and or Lycoming had wanted it done on an hourly interval, don’t you think they would have done so? But they didn’t. I don’t know why.

The point us, is don’t put yourself on a pedestal and think your smarter than them, it’s a hard position to defend, especially if something goes South.

Where are they cracked, fuel line side?

Military we did “phase” inspections, every 250 hours, and the crew chief did a through pre-flight ever 10 hours or 14 days whichever occurred first, we did not do major Calendar inspections that I can remember, but we aren’t Military. We are under FAA jurisdiction. I used to tell people I worked for who had the opinion that they owned the Company not the FAA, and therefore they could do what they wanted, that the FAA is like a Bear in the woods, you walk by the path for years and never see the Bear, pretty soon you wonder if there really is a Bear so you get lax, then one day for seemingly no apparent reason the Bear shows up and rips you to pieces.

It seems they really had rather not do their job, they had rather sit in the office, but if your going to make them fill out all this paperwork etc., they are going to push it and there will be some kind of enforcement action. 

Using your logic then how far a leap is it to decide an Annual is silly, I mean the thing only flew 20 hours last year, after all the inspection is usually called 100hr / Annual so why not wait until 100 hours?

It can be a slippery slope once you start, so don’t start is the only thing I know to do.

We used to have a saying in the Army for you to think about before you did something probably stupid, “how will it brief to the accident investigation board?”

Once the video was found, this one didn’t brief so well

I do five or six Annual’s a year, owner assisted and I’ve never charged my friends and neighbors, but will let them buy lunch or something. I’ve never made money from being an A&P / IA

Many may squall about the owner assisted part, but I figure it’s had two sets of eyes on it and I’m operating just as an inspector and I think it’s better / safer than me doing the work and inspecting myself. That was one difference in the Military, person performing the work was never allowed to inspect their own work.

Maybe you could get some Lawyer to argue the check list is just a guide and you can do whatever you think is important and only do AD’s, but I don’t want to be sitting there arguing that, don’t think it would brief well.

[DCarlton]

8 minutes ago, A64Pilot said:

You follow the checklist, if Mooney and or Lycoming had wanted it done on an hourly interval, don’t you think they would have done so? But they didn’t. I don’t know why.

The point us, is don’t put yourself on a pedestal and think your smarter than them, it’s a hard position to defend, especially if something goes South.

Where are they cracked, fuel line side?

Military we did “phase” inspections, every 250 hours, and the crew chief did a through pre-flight ever 10 hours or 14 days whichever occurred first, we did not do major Calendar inspections that I can remember, but we aren’t Military. We are under FAA jurisdiction. I used to tell people I worked for who had the opinion that they owned the Company not the FAA, and therefore they could do what they wanted, that the FAA is like a Bear in the woods, you walk by the path for years and never see the Bear, pretty soon you wonder if there really is a Bear so you get lax, then one day for seemingly no apparent reason the Bear shows up and rips you to pieces.

It seems they really had rather not do their job, they had rather sit in the office, but if your going to make them fill out all this paperwork etc., they are going to push it and there will be some king of enforcement action. 

Using your logic then how far a leap is it to decide an Annual is silly, I mean the thing only flew 20 hours last year, after all the inspection is usually called 100hr / Annual so why not wait until 100 hours?

It can be a slippery slope once you start, so don’t start is the only thing I know to do.

We used to have a saying in the Army for you to think about before you did something, “how will it brief to the accident investigation board?”

Once the video was found, this one didn’t brief so well

I do five or six Annual’s a year, owner assisted and I’ve never charged my friends and neighbors, but will let them buy lunch or something. I’ve never made money from being an A&P / IA

Many may squall about the owner assisted part, but I figure it’s had two sets of eyes on it and I’m operating just as an inspector and I think it’s better / safer than me doing the work and inspecting myself. That was one difference in the Military, person performing the work was never allowed to inspect their own work.

Maybe you could get some Lawyer to argue the check list is just a guide and you can do whatever you think is important and only do AD’s, but I don’t want to be sitting there arguing that, don’t think it would brief well.

I retired from the Navy after 35 years as a civilian engineer.  That's where I developed my paranoia regarding maintenance induced failures.  Every time someone turns a wrench, removes a healthy component, and reinstalls it, I somehow need to understand it's necessary even if it's just reading the recommended service bulletins.  But yes, understand if you're a professional mechanic you have to follow recommendations otherwise, you'll get eaten by that bear you mentioned.  A few mechanics know their customers and their customers airplanes and operating environment well enough to know what makes sense though and how to steer them where to invest in phased maintenance.  But again, I'm no expert, just a guy with an opinion.