Fuel Injector Cleaning - At Annual ?

[DCarlton]

Curious how often folks clean their fuel injectors?  Is it something you do at annual or only if experiencing issues?  If removed, are you ever concerned about effecting the integrity of the fuel lines from the flow divider?  And if so... how do you know when those fragile looking fuel lines need to be replaced?  And... if one breaks or leaks, does the flow divider stop the flow or do you get a fuel spray on a hot engine?  So many questions...  

Appreciate any opinions.  I'm in annual now.  Never seem them removed unless necessary.  Thanks.

[Will.iam]

My first annual that i had after purchase i took it to an MSC they took the injectors out to clean them. #5 injector was way too tight and almost stripped the nut face off it to remove it. Trying to find another injector was expensive and no guarantee that it would be matched to the other 5 injectors. I think spruce wanted like $250 for it. Well $900 got me 6 gami injectors and if one of those was not matched i could replace it for the correct flow size for free in the first year so i went with that. Have not started my second annual yet so not sure if this is an annual requirement or not. 

[EricJ]

8 minutes ago, DCarlton said:

Curious how often folks clean their fuel injectors?  Is it something you do at annual or only if experiencing issues?  If removed, are you ever concerned about effecting the integrity of the fuel lines from the flow divider?  And if so... how do you know when those fragile looking fuel lines need to be replaced?  And... if one breaks or leaks, does the flow divider stop the flow or do you get a fuel spray on a hot engine?  So many questions...  

Appreciate any opinions.  I'm in annual now.  Never seem them removed unless necessary.  Thanks.

Is there a concern that some are dirty or clogged?   If not, consider not disturbing them until/unless there is a reason to do so.   The cleaning process can be hard on the injectors if overdone or done improperly, so there is risk associated with unnecessary cleaning.

The lines should be visually inspected for support and integrity at every annual.  If they are properly supported, which is required to be inspected, there is little risk of issues with the lines and they tend to last the life of the engine if properly maintained.

There are failure modes of various components where fuel can get sprayed around the engine compartment, but they are rare and that's one reason why things are supposed to get inspected every year.   

[PT20J]

There are different theories. I had one clog at about 325 hours on my Lycoming IO-360. So now I clean them every 200. However, to minimize the chance of any maintenance induced problems, I use the Precision Airmotive RSA service and maintenance manual procedure which is minimally invasive. I simply remove the inserts and soak them in Hoppes No. 9 and blow out the bodies - still in the cylinder heads - with compressed air. If you remove the whole injector to soak it don't leave it in the Hoppes longer than about 20 minutes as the Hoppes will etch the brass. And don't mix the inserts -- they need to go back in the body from which they were removed. I do this at annual since disturbing the injector lines invokes the inspection required by AD 2015-19-07 which must be signed off by an A&P.

Skip

[RobertGary1]

If you have an engine monitor you can tell without removing them. Pretty rare to find anything. 

[Fly Boomer]

1 hour ago, DCarlton said:

Curious how often folks clean their fuel injectors?  Is it something you do at annual or only if experiencing issues?  If removed, are you ever concerned about effecting the integrity of the fuel lines from the flow divider?  And if so... how do you know when those fragile looking fuel lines need to be replaced?  And... if one breaks or leaks, does the flow divider stop the flow or do you get a fuel spray on a hot engine?  So many questions...  

Appreciate any opinions.  I'm in annual now.  Never seem them removed unless necessary.  Thanks.

I think it was George Braley or one of the APS guys who pointed out

1. 100LL is an excellent solvent, and the injectors see a lot of it

2.  The number one contaminant seen in an injector is red fiber from a rag

[N201MKTurbo]

1 hour ago, PT20J said:

There are different theories. I had one clog at about 325 hours on my Lycoming IO-360. So now I clean them every 200. However, to minimize the chance of any maintenance induced problems, I use the Precision Airmotive RSA service and maintenance manual procedure which is minimally invasive. I simply remove the inserts and soak them in Hoppes No. 9 and blow out the bodies - still in the cylinder heads - with compressed air. If you remove the whole injector to soak it don't leave it in the Hoppes longer than about 20 minutes as the Hoppes will etch the brass. And don't mix the inserts -- they need to go back in the body from which they were removed. I do this at annual since disturbing the injector lines invokes the inspection required by AD 2015-19-07 which must be signed off by an A&P.

Skip

The orifice in the inserts (0.028) are very well made. I have mixing them for years. Never any hint of inequality. The air bleed holes are very precisely machined too. Can’t imagine how mixing them up would cause any issue.

I have had them go unequal and found varnish build up on the inserts. I tried to measure them with gauge pins. One of them would not pass a 0.028- gouge pin (0.0275). I tapped it through the insert and a cylinder of varnish came out. They worked perfect after that. I inspected the bore by focusing a microscope down the bore of the insert and there was no sign of any scoring or anything after driving the pin through the orifice.

[PT20J]

25 minutes ago, N201MKTurbo said:

The orifice in the inserts (0.028) are very well made. I have mixing them for years. Never any hint of inequality. The air bleed holes are very precisely machined too. Can’t imagine how mixing them up would cause any issue.

I have had them go unequal and found varnish build up on the inserts. I tried to measure them with gauge pins. One of them would not pass a 0.028- gouge pin (0.0275). I tapped it through the insert and a cylinder of varnish came out. They worked perfect after that. I inspected the bore by focusing a microscope down the bore of the insert and there was no sign of any scoring or anything after driving the pin through the orifice.

All I know is what Al Jesmer and Peter Nelson at Precision Airmotive told me during a factory tour. When they assemble the nozzles at the factory, they run calibration fluid through them on a flow bench. They don't actually measure the flow, but look for the stream of fluid coming out of the nozzle. If it is a solid steam about the diameter of a number 2 pencil lead then it's good. If it is distorted or cone shaped, then they swap around inserts until it's good. I didn't ask how often they get a bad one. Maybe it's rare. But even if you mix them up, it's easy to test since they were all good when they left the factory. Just do the baby bottle test and watch the stream with the boost pump on. If they aren't all good, you can move the inserts around until they are. But, I'm betting that it is rare that mixing them up has an effect just by looking at the way they are made. Still, though, it's easy to test.

Skip

[DCarlton]

Appreciate the discussion.  I would be inclined to leave them alone unless there is some sign of a problem.  I do have an engine monitor.  I’ll discuss with the new shop tomorrow and get a better feel for their philosophy.  Manipulating those proven fuel lines for no reason makes me uncomfortable.  Would be curious to know what they’re made of and whether they work harden.  

[EricJ]

8 minutes ago, DCarlton said:

Appreciate the discussion.  I would be inclined to leave them alone unless there is some sign of a problem.  I do have an engine monitor.  I’ll discuss with the new shop tomorrow and get a better feel for their philosophy.  Manipulating those proven fuel lines for no reason makes me uncomfortable.  Would be curious to know what they’re made of and whether they work harden.  

They're steel.   

[PT20J]

26 minutes ago, EricJ said:

They're steel.   

Stainless

[PT20J]

42 minutes ago, DCarlton said:

Appreciate the discussion.  I would be inclined to leave them alone unless there is some sign of a problem.  I do have an engine monitor.  I’ll discuss with the new shop tomorrow and get a better feel for their philosophy.  Manipulating those proven fuel lines for no reason makes me uncomfortable.  Would be curious to know what they’re made of and whether they work harden.  

There is no reason to fear disconnecting the lines because you don't have to bend them as there is plenty of give. The reason for the AD is that sometimes after engine overhaul or maintenance some Adel clamps get left off and then the vibration of the unsupported lines causes them to crack. As long as they are clamped according to Lycoming's specs they are fine. 

I waited for some indication that they needed cleaning and what I got was suddenly a 3 cylinder engine during an IFR flight. Luckily, going full rich cleared it. But it happened again an the next leg. Full rich cleared it again and when I got home I pulled them and the offending cylinder injector had an obvious restriction of some sort of glop.

Skip

[Guest]

For a Lycoming, clean and install per S/I 1275C.  Hobbs 9 and 10 minutes in an ultrasonic cleaner does wonders.  Continental doesn’t have a service bulletin, see you have to refer the the manual.

I’ve seen cracked and stripped nuts as well as cracked injector bodies from over torquing the line nuts

[Shadrach]

9 hours ago, DCarlton said:

Curious how often folks clean their fuel injectors?  Is it something you do at annual or only if experiencing issues?  If removed, are you ever concerned about effecting the integrity of the fuel lines from the flow divider?  And if so... how do you know when those fragile looking fuel lines need to be replaced?  And... if one breaks or leaks, does the flow divider stop the flow or do you get a fuel spray on a hot engine?  So many questions...  

Appreciate any opinions.  I'm in annual now.  Never seem them removed unless necessary.  Thanks.

We don’t worry about removing them but don’t do so needlessly. I can see clearly on each flight if there is a fuel delivery problem.  In the past, I have seen maintenance induced problems. Once in the form of cracked flanges from over tightened b-nuts and the other in the form of a loose injector that had probably been cross threaded initially.  
 

How many of you that remove them regularly find them to be dirty?

[M20F]

Thoughts from a Mike Busch article. 
 
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.

[DCarlton]

Obviously different opinions.  Thanks.  Perhaps it's better to base it on hours of use.  The shop I'm working with now maintains flight school aircraft that get run hard.  With liability always a concern, I could understand a policy to clean injectors.  I'm the only guy that flies my plane.  If something works well, and is proven, I'm inclined to leave it alone if it requires wrenching unless there is a clear driver to perform preventative maintenance.  

But I'm no expert, just a pilot that has to feel good about his equipment in order to enjoy flying...  

[M20F]

7 minutes ago, DCarlton said:

But I'm no expert, just a pilot that has to feel good about his equipment in order to enjoy flying...  

Mike Busch is an expert.  Recommend at minimum picking his books up.  

[A64Pilot]

I clean mine at annual, I have four small baby food jars that are numbered, I put one injector in each with the Hoppes of course and they go into the ultrasonic.

Want to get a seized injector, leave it installed for a long time. You have to inspect the lines at annual anyway, I do so every time I have the cowling off. Those lines are actually pretty tough but one chafed through or a cracked line could be really, really bad so why not look?

I had a C-210 that would clog an injector occasionally, first time it did it, I went full rich and boost on to keep that cylinder EGT down, the rest went slobbering rich.

After that if it clogged again I left mixture alone and just let that cyl lean out and die, figured it was safer that way.

But then I clean and rotate plugs at every oil change too, while some won’t until one fouls. I’ve never had a plug foul.

Ever listened to your engine shortly after shutdown? Heard the crackling, sizzling sound? That’s the fuel boiling away as it boils off it can leave a varnish like deposit or lead behind.

https://www.lycoming.com/sites/default/files/Cleaning Fuel Injector Nozzles.pdf

[PT20J]

I’m sure @A64Pilot knows this, but in case others don’t…

Most people comply with the fuel line AD at annual, but for some silly reason the actual compliance interval is every 110 hours, so be mindful if you fly a lot.

if an injector clogs, the other cylinders get the fuel that is not going through that injector because the flow is constant up to the divider inlet and the fuel has to go somewhere.

[A64Pilot]

10 minutes ago, PT20J said:

 

if an injector clogs, the other cylinders get the fuel that is not going through that injector because the flow is constant up to the divider inlet and the fuel has to go somewhere.

For the same reason a broken line can have almost all of the fuel dumping out of the break onto a hot engine, the fire possibility scares me more than an engine failure

[DCarlton]

20 minutes ago, A64Pilot said:

I clean mine at annual, I have four small baby food jars that are numbered, I put one injector in each with the Hoppes of course and they go into the ultrasonic.

Want to get a seized injector, leave it installed for a long time. You have to inspect the lines at annual anyway, I do so every time I have the cowling off. Those lines are actually pretty tough but one chafed through or a cracked line could be really, really bad so why not look?

I had a C-210 that would clog an injector occasionally, first time it did it, I went full rich and boost on to keep that cylinder EGT down, the rest went slobbering rich.

After that if it clogged again I left mixture alone and just let that cyl lean out and die, figured it was safer that way.

But then I clean and rotate plugs at every oil change too, while some won’t until one fouls. I’ve never had a plug foul.

Ever listened to your engine shortly after shutdown? Heard the crackling, sizzling sound? That’s the fuel boiling away as it boils off it can leave a varnish like deposit or lead behind.

https://www.lycoming.com/sites/default/files/Cleaning Fuel Injector Nozzles.pdf

Interesting.  Lycoming says "at overhaul or as engine conditions require".  Not very helpful in terms of periodicity.  

[PT20J]

AvStar (current OEM supplier of fuel injection systems to Lycoming) says annually or 100 hrs, whichever comes first. That’s why I said in my initial post that opinions vary. In truth, the only thing you’ll know for sure is that if one clogs, you waited too long. 

[Shadrach]

2 hours ago, PT20J said:

the only thing you’ll know for sure is that if one clogs, you waited too long. 

So for those that have had injectors clog in flight, when should they have cleaned them to avoid being part of the scofflaws that “waited too long”? Have you seen a lot of gradual clogging that is remedied by a good soak? I’m not saying  Avgas is the best solvent but it’s a pretty reasonable solvent for what’s in the fuel system (avgas) and when operating it’s being pushed to the nozzle inlet at varying pressures up to ~50psi. Seems to me that most clogs are debris related and really don’t care when the injectors were last cleaned, unless said debris was introduced during cleaning.

I’m in annual next month, I think I will pull them just to see how they look. I’ll also note full rich EGTs before and after to see if it makes a difference. I don’t regularly pull them, but I’m willing to change my SOP if there’s a visible or measurable benefit.

[Will.iam]

1 hour ago, Shadrach said:

So for those that have had injectors clog in flight, when should they have cleaned them to avoid being part of the scofflaws that “waited too long”? Have you seen a lot of gradual clogging that is remedied by a good soak? I’m not saying  Avgas is the best solvent but it’s a pretty reasonable solvent for what’s in the fuel system (avgas) and when operating it’s being pushed at the nozzle inlet at varying pressures up to ~50psi. Seems to me that most clogs are debris related and really don’t care when the injectors where last cleaned, unless said debris was introduced during cleaning.

I’m in annual next month, I think I will pull them just to see how they look. I’ll also note full rich EGTs before and after to see if it makes a difference. I don’t regularly pull them, but I’m willing to change my SOP if there’s a visible or measurable benefit.

Keep us posted. I’d like to know what you find out. 

[EricJ]

I had an injector clog, and it was from some kind of debris, not any sort of gradual crud accumulation.   The rest of the injectors were fine, and the one that clogged was fine once we blew the chunk of whatever-it-was out of it.

I suspect a significant maintenance procedure that would help prevent injector clogs is regular inspection/cleaning of the finger filter in the servo (for Lycomings, anyway).   If there's no crud there, there's unlikely to be crud get to the injectors.    When my injector clogged, the finger filter was full of junk, and at the time I didn't know it but I had a servo failure in my future as well.  Keeping the upstream stuff clean goes a long way toward happy injectors.