How do Injectors Fail?

[brcase]

Been flying behind a Lyc IO360 regularly for the past few months.

1st for sure event, fueled the plane ran it up, all ok and parked it. Next morning taxied out for departure at 1800rpm mag check was ok, but was just a bit rough and #2 EGT looked a bit off (I think colder than normal). Tried to do a full power run up and above 2000rpm, #2 cylinder went completely cold on both Mags. Taxied back, got injector cleaned and all was good.

About 12 flight hours later and a month later had almost the same thing happen on the #2 injector
Cleaned the injector and swapped it with the #4 injector.

About 6 flight hours and 2 weeks later Mid flight the #4 injector plugged again (running very rough), going full rich mostly smoothed it out.

3 strikes your out, That injector is getting replaced (not cleaned again). I always thought injectors were pretty fool proof, essentially a precision diameter and shaped hole to meter and spray fuel. Is there more to it than that, what about an injector would cause it to repeatedly clog?

Brian

 

[Let'sgoflying!]

something flowing downstream into the injector, the rubber diaphragm in the divider?
Need to pay attention to what it is getting clogged with.

 

[mondtster]

These injectors are simple fixed orifices. They won’t really “fail” but rather get clogged with some trash that makes its way into the injector. I’d suggest finding the source of the trash rather than replacing the injector.

 

[Clip4]

Maybe it’s you fuel system and not the injector. The hoses under the cowling are typilly replaced on a scheduled basis, rubber line connections from the tanks are not. Deteriorating tank bladders….

You are buying cruddy fuel.

 

[Oldmanb777]

Wasn't there an AD on the diaphragms a number of years ago for exactly that. As said, i would be looking at what is plugging the injector, and trace that to the source. Injectors don't fail. Just an orifice. Unlike automotive that are electric (solenoid) pintle valves.

 

[Dan Thomas]

There are so many filters in an injected system that there's no way it could get clogged with fuel system debris unless those filters aren't being maintained. There's the finger screen in the tank. Coarse screen. There's the fuel strainer, a fine screen. There's the injector servo inlet strainer, and really fine screen. There's the last-chance screen, another really fine screen, in the injector manifold.

That said, we once had issues with paint flakes getting into injectors. The airplane had been painted, engines off it, and they hadn't taped shut the bulkhead fittings. Paint got into the fuel fittings and broke free and got past the last two filters, which must have been loose or poorly installed.

More often it's stuff that gets in when the injector lines are disconnected for maintenance. And with a turboed engine, you have the pressurized injectors that can get junk blown into them. The normally-aspirated engine's injectors have a tiny screen under a shield that lets the fuel draw air in for atomization. That won't work with a boosted engine. The boost would push the fuel out of that screen. So the injectors are fed air from the intake manifold to equalize the pressures.