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.