Injector Cleaning


Guess what we're doing here. If you own a fuel injected aircraft engine and do your own maintenance, you probably recognize the process – we’re cleaning fuel injector nozzles.

Our RV-3 has purred as smooth and soft as a kitten from day one. With dual P-Mags and a Bendix-style injector set-up, you can pull the mixture back until well after the EGT peaks, and it stays smooth – right up until about 200 degrees lean of peak when it just stops firing. Really a sweet engine.

Until recently that is. Just the other day I started to get roughness and even a little backfiring as I tried to lean it to our normal LOP position. Looking at the engine monitoring pages on the EFIS, there wasn’t an obvious ignition problem with one cylinder – so I figured that with 560 hours on the motor, it probably wouldn’t hurt to see if I had a dirty injector nozzle.

Pulling the cowl took a few minutes, and the nicely placed nozzles (right on top of the cylinder heads) made getting them out a piece of cake. I choose to do them one at a time, just to make certain that I don’t mix them up. General airport wisdom (and the maintenance manual) suggest cleaning the injectors in Hopps #9 gun cleaning solvent, and it does, indeed, work quite well. At least one manual I have suggests cleaning them in the solvent in an ultrasonic jewelry cleaner, like the one shown here (about $25 at your local big-box store.

Giving each injector a couple of minutes in the cleaner, I reinstalled them, buttoned things up – and sure enough, the kitten was back. Yeah – I did check the spark plugs while I was in there too…. they were all in good shape, nothing fouled….so we’re back in the air. I figure that cleaning the injectors once in a while sure can’t hurt.


Paul Dye

Paul Dye, Kitplanes® Editor at Large, retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the space shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 and a Subsonex jet that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra they completed. Currently, they are building a Xenos motorglider. A commercially licensed pilot, he has logged over 5000 hours in many different types of aircraft and is an A&P, EAA Tech Counselor, and Flight Advisor, as well as a member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.

2 Replies to “Injector Cleaning”

  1. Dear Paul, I have nearly the same engine ... TMX-IO-320 ... the same as yours, "one of the last one from Long Island, Mattituck"!

    Would be good if you write something about the B-Nut torque and how do you apply it. Often I see people that strip the B-Nut or heavily over tightening them! You do not want them to come loose from under or over tightening in flight.
    Maybe you have something to tell us from your experience or make an interview with Don Rivera or so.

  2. Paul, in the photo of your cleaned injector, I see a crack starting in the baffle at the baffle mounting screw. You may want to stop drill it. Nice article.

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