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Fuel Injector Cleaning - At Annual ?


DCarlton
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2 hours ago, Shadrach said:

:lol: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.

That's an excellent question. I used to clean injectors every annual and never had a clog. I let them go to 300+ hours to minimize maintenance and had one clog. But, the sample size is too miniscule to be statistically significant. BTW, when mine clogged, I did pull the finger screen out of the injector body and it was clean. The stuff in my injector appeared to be some sort of build up in the restrictor. The injector lines had not been touched since the rebuilt engine arrived from the Lycoming factory, so I don't believe it was caused by any foreign matter getting into the fuel system.

 

Mogas has detergent additives to keep the fuel injectors clean. Auto manufacturers apparently believe it important enough that they have developed a specification www.toptiergas.com. Chevron https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf describes the cause of injector deposits as follows:

Port fuel injector (PFI) deposits form during the hot soak
period after an engine has been turned off. The gasoline
trapped in an injector tip is exposed to a higher temperature
for a longer time than the gasoline that flowed through the
injector when the engine was running. The heat degrades the
gasoline into a hard varnish, initiating deposit formation. In
the absence of an effective additive, injector deposits form
quite rapidly if a base gasoline is relatively unstable and if
a vehicle is used predominantly for short trips. 

Chevron's Avgas does not appear to have detergent additives. It does have an antioxidant that I believe is added to improve stability during storage. https://www.chevron.com/-/media/chevron/operations/documents/aviation-tech-review.pdf

What's it all mean? I don't know. But I know that the two injector manufacturers recommend periodic cleaning and I figure it can't hurt anything if appropriate care is taken and it is easy to do. But it could be a waste of time.

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44 minutes ago, PT20J said:

Mogas has detergent additives to keep the fuel injectors clean. Auto manufacturers apparently believe it important enough that they have developed a specification www.toptiergas.com. Chevron https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf describes the cause of injector deposits as follows:

Skip

 

Even running Top Tier gas, I find a bottle of Chevron Techron every so often keeps my gas mileage higher.  No Chevron stations around to just buy the gas with it in it.

In the 90s, we put 349,000 miles on a Jeep Cherokee.  We keep records every fill up.  Gas mileage would start going down (filled with whatever station was handy or cheap), I would fill up with Mobil Premium.  The gas mileage would go back and stay up for a while.

I wonder why nothing like Techron for aircraft????

 

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42 minutes ago, PT20J said:

Mogas has detergent additives to keep the fuel injectors clean. Auto manufacturers apparently believe it important enough that they have developed a specification www.toptiergas.com. Chevron https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf describes the cause of injector deposits as follows:

Port fuel injector (PFI) deposits form during the hot soak
period after an engine has been turned off. The gasoline
trapped in an injector tip is exposed to a higher temperature
for a longer time than the gasoline that flowed through the
injector when the engine was running. The heat degrades the
gasoline into a hard varnish, initiating deposit formation. In
the absence of an effective additive, injector deposits form
quite rapidly if a base gasoline is relatively unstable and if
a vehicle is used predominantly for short trips. 

Chevron's Avgas does not appear to have detergent additives. It does have an antioxidant that I believe is added to improve stability during storage. https://www.chevron.com/-/media/chevron/operations/documents/aviation-tech-review.pdf

What's it all mean? I don't know. But I know that the two injector manufacturers recommend periodic cleaning and I figure it can't hurt anything if appropriate care is taken and it is easy to do. But it could be a waste of time.

Skip

Automotive and aviation fuel injectors aren't very comparable, imho, and in this context maybe neither is avgas and mogas.    I've never seen avgas turn into the same sludge that mogas will make if left alone.   Automotive injectors turn off electronically and control mixture by pulse width (on time) at the beginning of the intake stroke.   So they do store a little fuel in the injector since it is turned off at shutdown.   Our sloppy "injectors", (nozzles, actually) don't do that, so aren't subject to quite the same issues, especially with avgas instead of mogas.   It might be interesting to see whether the new iE2 Lycoming engines with electronic injectors have any issues similar to those described for autos, which are still pretty rare even in that space.    In my experience automotive injectors tend to wear/age rather than clog.

Not sure what you had going in yours, but I don't think you're the only one that has experienced that, either.

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1 hour ago, EricJ said:

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.

Many maintainers don’t seem to know where the finger screen is from some of the post’s I’ve seen here.

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8 minutes ago, ilovecornfields said:

They can actually do something pretty similar now with IVC filters and catheter directed thrombolytics. 

That guy certainly does inspire confidence.

I was consulting at my ex-employer and walked the floor to see what they are up to these days. They are building machines to manufacture those things.

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FWIW,

I've never had an injector clog in flight, and I don't think cleaning would have any effect on clogging. I have had them get coated with varnish and change the nozzle orifice size, but that happened over many months and was very gradual. 

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26 minutes ago, ilovecornfields said:

They can actually do something pretty similar now with IVC filters and catheter directed thrombolytics. 

That guy certainly does inspire confidence.

I had a babysitter that let me watch  Cannonball Run when I about 8 years old. I did not get many of the jokes, but I thought Dr. Nikolas Van Helsing (above) was hilarious!

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I've done owner assist annuals for the past 8 years, and 5 of those years religiously we pulled the injectors and cleaned them in Hoppes. In 2019 a nut was put on incorrectly on one of the injectors. It leaked and showed up with different readings on that cylinder, etc. It took awhile to figure that out. We then switched to pulling the injectors every other year. After reading this thread I'm definitely satisfied with every two or three years.

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14 hours ago, DCarlton said:

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...  

what type of flying would you classify as being hard on an injector. The only time I’ve ever seen issues is when they’ve been opened and something got in them. Like a piece of dust 

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11 hours ago, RobertGary1 said:

what type of flying would you classify as being hard on an injector. The only time I’ve ever seen issues is when they’ve been opened and something got in them. Like a piece of dust 

None; poor use of words on my part.  Just a lot of hours.  As opposed to my flying which might be 50 hours a year.  My guess is the shop is using the aforementioned AVSTAR recommendation (every 100 hours or at annual).  The Lycoming recommendation doesn't help much (at overhaul or as necessary).  Like I mentioned, I'm just an engineer and private pilot with an opinion; not a professional mechanic but I'm fine with extending the periodicity for cleaning on my personal airplane.  

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13 hours ago, RobertGary1 said:

what type of flying would you classify as being hard on an injector. The only time I’ve ever seen issues is when they’ve been opened and something got in them. Like a piece of dust 

If the cause of deposits is heat deterioration of the fuel in the injectors after shutdown as the Chevron mogas document claims, then a lot of short flights might be more problematic. I use my plane frequently to go between my home airport and another airport 13 minutes away. Just a thought. 

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22 hours ago, M20Doc said:

Many maintainers don’t seem to know where the finger screen is from some of the post’s I’ve seen here.

Most of the people on this thread don’t know what they are talking about, but that is what makes the Internet entertaining. 

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The most interesting injector clogs we have seen around here…

Have been found using the baby food jar test…

It is important to catch the blockage when cleaning it out…

Definitely want to know what is in there…

Hoppes is known for its ability to dissolve lead which is common in 100LL…

Use caution with soaking too long… remember there is lead in brass alloys… a few percent…

 

The important ones are made of small rubber bits…

A sign that something rubber lined upstream has reached its limit…

Oddly… there is often a fuel line in front of the fuel injection system that has a rubber lining…

Sooo… when you have a fuel injector blockage… catch and post a pic!

PP thoughts only, not a mechanic…

Best regards,

-a-

 

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Clogs and restriction are different things, ask anyone with hardening of the arteries, they can educate you in the difference.

The clogs I would get in the 210 were all of the sudden a cyl would go dead from a particle blocking it, pretty sure it was a deteriorating fuel hose.

Restrictions on the other hand can be a slow build up over time of a varnish like material that of course reduces flow.

I find it interesting that a group that will pay money for tuned injectors doesn’t want to clean them to ensure they remain tuned.

Jet-A is a good solvent too, ask anyone who maintains a PT-6 how important regular removal of the fuel nozzles for cleaning is.

 

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7 hours ago, M20F said:

Most of the people on this thread don’t know what they are talking about, but that is what makes the Internet entertaining. 

I’ve observed a couple of opposed schools of thought in this thread.  Both with valid points.  I’ve also learned that AVSTAR, Lyc, and Mooney all have published recommendations.  The published recommendations are the most cautious and conservative.  Not surprising.  If a shop insists their policy is to do it annually, I won’t argue with it.  Can’t expect them to go against published guidance.  If the engine is running fine, and a shop says they don’t recommend it, I’m ok with that too.  Appreciate the discussion.  

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18 minutes ago, DCarlton said:

I’ve observed a couple of opposed schools of thought in this thread.  Both with valid points.  I’ve also learned that AVSTAR, Lyc, and Mooney all have published recommendations.  The published recommendations are the most cautious and conservative.  Not surprising.  If a shop insists their policy is to do it annually, I won’t argue with it.  Can’t expect them to go against published guidance.  If the engine is running fine, and a shop says they don’t recommend it, I’m ok with that too.  Appreciate the discussion.  

The key thing…

People that like to have the injectors cleaned… really know their mechanics….   :)
 

Often doing a baby food jar test… you probably want to see it yourself…

Looking for the unexpected things like air bubbles flowing in the line… (sign of a leak upstream…)

 

There are a few different ways to create maintenance induced errors…

Some are as easy as knowing where the mark on the fuel injector belongs when it is installed… and what that letter means…

A few injectors have been installed upside down around here… the tiny vent hole becomes a tiny leak hole… leaving a blue stain…

 

PP thoughts only, not a mechanic….

Best regards,

-a-

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The best buck and a quarter you will ever spend is to buy an ultrasonic cleaner from Amazon. I bought the iSonic P4820. My mechanic was so impressed......I gave it to him and bought another for me. Put the injector in a small plastic cup with Hoppes. Set the cup in water in the ultra-sonic and you get surgically clean injectors, very quickly. 

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1 hour ago, GeeBee said:

The best buck and a quarter you will ever spend is to buy an ultrasonic cleaner from Amazon. I bought the iSonic P4820. My mechanic was so impressed......I gave it to him and bought another for me. Put the injector in a small plastic cup with Hoppes. Set the cup in water in the ultra-sonic and you get surgically clean injectors, very quickly. 

Also great for Ford Model T carbs, lawnmower carbs, the Wife’s jewelry and many other jobs. Don’t use it on soft stones like Opal though. I like heated ones it seems hot cleaning fluid works better and faster.

Grew up using one in my Father’s Dental Office, he used 50/50 Mr Clean and water to clean lab instruments etc. Was always warned to not put your fingers in while it was running to remove things, not sure if that’s really bad or not. 409 is also good.

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10 hours ago, GeeBee said:

The best buck and a quarter you will ever spend is to buy an ultrasonic cleaner from Amazon. I bought the iSonic P4820. My mechanic was so impressed......I gave it to him and bought another for me. Put the injector in a small plastic cup with Hoppes. Set the cup in water in the ultra-sonic and you get surgically clean injectors, very quickly. 

The indirect cleaning method, saves chemicals.  Loved by CB’s everywhere.

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