How to Clean Injectors

[PT20J]

I use Hoppes #9 also. But it is interesting that apparently Lycoming is the only one that recommends it. It's not mentioned by Precision or Avstar in their service literature. I think Hoppes may be recommended because it removes lead deposits (it's a firearm cleaner) but I'm not sure, and I don't know if any lead will precipitate out of the TEL in avgas. The MSDS lists ammonium yydroxide as a component and that chemical will attack brass. One A&P at the Lycoming factory class said she left some injectors in Hoppes for an extended time (over a weekend? Don't remember) and it damaged them. I believe others have not seen this issue. I do note that the Lycoming SI says to only soak in Hoppes for 20 min whereas it says to soak in MEK or acetone for an hour. It also says to rinse with Stoddard solvent after soaking in Hoppes.

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[A64Pilot]

1 hour ago, PT20J said:

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

I don’t think they got the federal mandate which is surprising considering the effects of carbon build up on emissions.

Most of the automakers banded together and came up with a set of standards higher than federally mandated, this is called top tier fuel and has been around for almost 20 years, the below links explain it better than I can, there are many others of course, many even low cost fuels meet top tier, but many don’t. It’s worth buying.

https://en.wikipedia.org/wiki/Top_Tier_Detergent_Gasoline

https://www.consumerreports.org/cars/fuel-economy-efficiency/top-tier-gasoline-worth-the-extra-price-a7682471234/

[PT20J]

Just now, A64Pilot said:

I don’t think they got the federal mandate which is surprising considering the effects of carbon build up on emissions.

Most of the automakers banded together and came up with a set of standards higher than federally mandated, this is called top tier fuel and has been around for almost 20 years, the below links explain it better than I can, there are many others of course, many even low cost fuels meet top tier, but many don’t. It’s worth buying.

https://en.wikipedia.org/wiki/Top_Tier_Detergent_Gasoline

https://www.consumerreports.org/cars/fuel-economy-efficiency/top-tier-gasoline-worth-the-extra-price-a7682471234/

My understanding is that the auto manufacturers got the EPA to mandate a minimum standard. Then they came up with Top Tier that gave gasoline suppliers an opportunity to market a more expensive (and higher margin) product that exceeded minimums.

[A64Pilot]

17 minutes ago, PT20J said:

I use Hoppes #9 also. But it is interesting that apparently Lycoming is the only one that recommends it. It's not mentioned by Precision or Avstar in their service literature. I think Hoppes may be recommended because it removes lead deposits (it's a firearm cleaner) but I'm not sure, and I don't know if any lead will precipitate out of the TEL in avgas. The MSDS lists ammonium yydroxide as a component and that chemical will attack brass. One A&P at the Lycoming factory class said she left some injectors in Hoppes for an extended time (over a weekend? Don't remember) and it damaged them. I believe others have not seen this issue. I do note that the Lycoming SI says to only soak in Hoppes for 20 min whereas it says to soak in MEK or acetone for an hour. It also says to rinse with Stoddard solvent after soaking in Hoppes.

Skip

I don’t think Hoppes removes lead fouling, scrubbing does, that why wire brushes are used, for metal fouling. I used to shoot a lot of high velocity 22-250, 220 Swift and .204 Ruger, high velocity copper fouls as that’s what a bullet jacket is made from, Hoppe’s has pretty much no effect, but nearly pure Ammonia sure does, use it and patches come out green from oxidized copper.

However Hoppes is an excellent powder fouling cleaner and I believe powder fouling is mostly carbon, but not sure.

On edit, Hoppes claims to remove lead, but it also claims to remove rust. I believe that’s marketing, if you pushed I bet their answer would be if used according to instructions that is vigorous scrubbing with a wire brush that it does remove lead, but I bet vigorous scrubbing with a wire brush and WD-40 would also remove lead. My experience with it us that it has very limited or no effect on metal fouling, but suspect that a fuel injector never gets lead fouled anyway.

Acetone I believe has very little effect on most metals, it’s primarily I believe a very powerful de-greaser, maybe it’s for that varnish that was spoken about? Just guessing. It strips paint off of Bell Pitch change links well whatever that’s worth.

[A64Pilot]

12 minutes ago, PT20J said:

My understanding is that the auto manufacturers got the EPA to mandate a minimum standard. Then they came up with Top Tier that gave gasoline suppliers an opportunity to market a more expensive (and higher margin) product that exceeded minimums.

You may be right, but obviously what’s mandated isn’t good enough or they wouldn’t have pushed for and be recommending top fuel so hard, they even put it in owners manuals, not that anyone reads those  

[A64Pilot]

My solution for cleaning injectors, the smallest baby food jars and 1qt of Hoppes is $16 on Amazon

Put them in an ultrasonic and let them float in the water.

Jars are 2.5 oz if filled to the top, but you only need maybe an oz, just buy them at Walmart and dump the nasty out and wash them, empty one sell for more on Ebay than the ones full of food at Walmart.

 

[MikeOH]

24 minutes ago, A64Pilot said:

...just buy them at Walmart and dump the nasty out ...

 

 

 

Hey, the applesauce is pretty good

[N201MKTurbo]

57 minutes ago, A64Pilot said:

My solution for cleaning injectors, the smallest baby food jars and 1qt of Hoppes is $16 on Amazon

Put them in an ultrasonic and let them float in the water.

Jars are 2.5 oz if filled to the top, but you only need maybe an oz, just buy them at Walmart and dump the nasty out and wash them, empty one sell for more on Ebay than the ones full of food at Walmart.

 

Get the peaches, they are yummy!

[Fly Boomer]

4 hours ago, kortopates said:

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. 

I don't know about TCM vs Lyc, but the GAMI guys said the number one contaminate they find is a little bit of something from a red shop rag.

[kortopates]

I don't know about TCM vs Lyc, but the GAMI guys said the number one contaminate they find is a little bit of something from a red shop rag.

Yes, lint is very common and can clog the screen on a continental flow divider - over several years.


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[DonMuncy]

So the theory is that when fuel is run through the injector, a tiny amount will cling to the bore of the injector when the engine is stopped. The oxygen will then oxidize it, and then fuel flow through it when the engine is run again, will not remove it?

I'm not as smart as I thought I was.

Thanks for the education.

 

[ArtVandelay]

So the theory is that when fuel is run through the injector, a tiny amount will cling to the bore of the injector when the engine is stopped. The oxygen will then oxidize it, and then fuel flow through it when the engine is run again, will not remove it?

I think it’s the blue dye that leaves a residue, just like if you have a leaking fuel tank?

[EricJ]

47 minutes ago, ArtVandelay said:

I think it’s the blue dye that leaves a residue, just like if you have a leaking fuel tank?

The dye goo is soluble in gasoline, so if more gas comes along it'll get washed away.   The varnish isn't, and it'll stay once it starts building up.

[blaine beaven]

12 hours 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 never revealed any screen obstruction. The injector nozzles are spotless.

It made no appreciable change in the smoothness of the running. 
 

I’ve got an engine monitor going in this fall that will hopefully allow for some more in depth trouble shooting. 

[A64Pilot]

9 hours ago, DonMuncy said:

So the theory is that when fuel is run through the injector, a tiny amount will cling to the bore of the injector when the engine is stopped. The oxygen will then oxidize it, and then fuel flow through it when the engine is run again, will not remove it?

I'm not as smart as I thought I was.

Thanks for the education.

 

My theory is it’s as much heat as anything. Apparently almost any type of fuel as the volatiles flash off leave something behind, perhaps if it’s oxidized it becomes no longer soluable in the fuel.

This doesn’t happen to the insides of portable fuel tanks or just tanks making me think that heat has something to do with it, but also apparent air is required.

Any regular engine with a carburetor if left with fuel in it for long enough will gum up or varnish, we have all seen it, but a modern fuel injection system that keeps the fuel not exposed to any air can be stored for years even with alcohol fuel and it won’t gum or varnish, the difference is none of it is exposed to air, even the fuel tank is pretty well sealed to prevent pollution from evaporative loss.

I’ve not seen this in 100LL fuel myself though so you maybe cant make direct correlations with autofuel and Avgas.

Will the replacements for 100LL be as “pure” and store as well and not oxidize as well as Avgas? I suspect it will be similar to many of the blends of gasses for refrigerant are, that over time some of it is lost and it changes its properties as some of the components are lost. But time will tell.

[Pinecone]

Hoppes is more agressive than MEK.

Hoppes will not dissolve large amounts of lead (like in a firearm) but does soften in.  For an injector, it will damage the brass with an extended soak.

IMO, the best way to deal with the issue is to have an engine analyzer and clean them when one starts going leaner.  Otherwise, leave them alone.

[EricJ]

1 hour ago, Pinecone said:

Hoppes is more agressive than MEK.

More aggressive to the brass, but not to the mechanic.    MEK is nasty stuff, acetone as well but a bit less so.   Hoppes No. 9 is benign by comparison.   I can buy more nozzles if they get damaged, and preventing damage to the nozzles seems straightforward.

The nozzle pintle isn't brass (steel, apparently), and limiting the soak time per the SI should protect the rest of the nozzle.   Limiting cleanings to ~300 hours or when there's an issue requiring it as has been mentioned here should limit potential for damage to the nozzle even further.

[Shadrach]

15 hours ago, PT20J said:

I use Hoppes #9 also. But it is interesting that apparently Lycoming is the only one that recommends it. It's not mentioned by Precision or Avstar in their service literature. I think Hoppes may be recommended because it removes lead deposits (it's a firearm cleaner) but I'm not sure, and I don't know if any lead will precipitate out of the TEL in avgas. The MSDS lists ammonium yydroxide as a component and that chemical will attack brass. One A&P at the Lycoming factory class said she left some injectors in Hoppes for an extended time (over a weekend? Don't remember) and it damaged them. I believe others have not seen this issue. I do note that the Lycoming SI says to only soak in Hoppes for 20 min whereas it says to soak in MEK or acetone for an hour. It also says to rinse with Stoddard solvent after soaking in Hoppes.

Skip

I’m sure you’ll recall that last year I conducted an experiment with some old, unairworthy injectors that I had on hand. I soaked the injectors in Hoppes for as little as 20mins and as long as 5 days. The only visible difference was that the 5 day appeared much cleaner. There was no evidence of etching or deterioration that I could see. Now I’m not saying that the A&P in your class was being deliberately dishonest, but it’s not uncommon for people to integrate things they've been told into a personal story. On some level I think we’re psychologically predisposed towards doing so, but that’s another conversation.

Injector on left spent 5 days submerged  in Hoppes. Injector on right was submerged for 20 mins.

 

[N201MKTurbo]

If you read the history of Hoppes #9, they changed the formula a while back. The old version was too toxic for california. It is possible the old formula was more aggressive then the current formula.

This is what happens when you use a commercial product that does meet a MIL spec.

[Shadrach]

31 minutes ago, N201MKTurbo said:

If you read the history of Hoppes #9, they changed the formula a while back. The old version was too toxic for california. It is possible the old formula was more aggressive then the current formula.

This is what happens when you use a commercial product that does meet a MIL spec.

They took out the nitrobenzene about 20 years ago. It looks like it was precipitated by federal, not state regs. That being said, I think the stuff I used my experiment was the old stuff. It has a nice, almost bananaesque smell.

[Fly Boomer]

On 9/11/2023 at 10:20 AM, Shadrach said:

It looks like it was precipitated by federal, not state regs.

FWIW, California regs frequently drive federal regs.

[Shadrach]

6 minutes ago, Fly Boomer said:

FWIW, California regs frequently drive federal regs.

Meh. Cast a wide enough regulatory net and you will always be first.