Clogged fuel injector--now what?

Davepar · #1 04-01-2007, 11:54 AM

From what I've read, I have the classic symptoms of a clogged fuel injector: engine slightly rough, #4 EGT rising 100-200F above others, backfires when I pull the power back.

Now my question is what do I do? I can remove the fuel injector and poke something through it to clean the clog. Should I use some sort of cleaner?

I've read about a flow test. Is that just a matter of removing all the injectors and running them into containers and making sure they all produce the same amount of fuel per unit of time?

Thanks,
Dave

flyeyes · #2 04-01-2007, 12:22 PM

Quote:

Now my question is what do I do? I can remove the fuel injector and poke something through it to clean the clog. Should I use some sort of cleaner?

Don't poke anything through the hole. After carefully removing the injectors, you can soak them in Hoppe's #9 solvent (used for cleaning guns--you can find it a Walmart, BassPro, etc.) followed by MEK.

An ultrasonic cleaner like those used for jewlery is useful as well.

Keep track of which injector came out of which cylinder.

Be careful reinstalling--don't over torque them.

dan · #3 04-01-2007, 12:27 PM

My money is on a fouled plug. Imho a clogged injector would show up more as a skyrocketing EGT rather than just a rise. And you'd probably feel the roughness.

What does an in-flight mag/ignition check show?

DanH · #4 04-01-2007, 12:41 PM

Keep in mind that there is no reason to expect an injector clog to respond to solvent. You should use a good magnifier and look in the injector clog before you try to clean it. I have found a neat little coil of aluminum shaving at least once with a new airplane.

<<flow test.... running them into containers...they all produce the same amount of fuel per unit of time?>>

Yes.

Davepar · #5 04-01-2007, 02:01 PM

Thanks. I'll try the thorough cleaning and take a look at the plugs.

During run-up, EGTs were 1144, 1180, 1151, 1338. I didn't notice the differential, but did notice a slight roughness not isolated to one ignition or the other.

I took off. Power felt slightly reduced from my first flight (although my personal gauge isn't quite calibrated yet). Engine was running rough like one cylinder wasn't firing occasionally. EGTs were 1247, 1258, 1196, 1416. CHTs were 318, 346, 364, 314. Didn't seem terrible, but decided to play it safe. I turned into the downwind and landed.

odlee · #6 04-01-2007, 04:43 PM

Dave, I've had both fouled plugs(as have most of us) and an injector with restricted flow. The restricted flow egt went out of sight on takeoff and this was a brand new factory reman. A prompt return to the field revealed a machining chip lodged in the nozzle. A burnt valve for sure without an engine monitor. A fouled plug exhibits only a slight rise.

Good luck,
David

Davepar · #7 04-01-2007, 10:23 PM

I took out the fuel injector. There was a tiny bit of something lodged in it. Got it out, but it fell on the hangar floor before I could identify it. I looked at the plugs. They both looked fine, although I don't know what a fouled plug would look like. The bottom one was a little oily on the threads, but I've heard that's common until the rings seat.

I went back up for circles over the airport and it ran like a champ. Now I just need to figure out if my high CHTs are real or a sensor problem. The back two are running at 400F or a little over at 24/2400 in level flight with <50F OAT.

panhandler1956 · #8 02-10-2013, 12:54 PM

I may have this too. I replaced my plugs (they needed it) and hopped in expecting my serious stumble on takeoff to go away - it didn't. I aborted the takeoff. I do have high EGT on one cylinder, thought it was a bad probe.

I'll pull the injectors and see what I find. I assume chemtool carb cleaner is ok?

jetdriven · #9 02-10-2013, 01:48 PM

I put the injector bodies and inserts in a Harbor Freight ultrasonic cleaner with Hoppes #9 (you can also use MEK or Acetone per Lycoming). Run them 30 minutes in the ultrasonic cleaner, then spray liberally in both directions separately. Allow to dry a minute, inspect with a magnifying glass, then fit the insert, and install with clean hands and a clean extra deep 12" socket. Per Lycoming's directions, torque 60 IN LB then turn further till the "A" stamped on the side of the nozzle is on the bottom. Careful here.

I keep the individual injectors soaking in separate, numbered glasses and rotate them into the ultrasonic cleaner.

LettersFromFlyoverCountry · #10 02-10-2013, 02:02 PM

Reading this thread, I got all excited when I saw Checkoway replied. Then I realized that someone brought back a 6-year-old-thread.