FADEC Caution flicker

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cirimj82
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FADEC Caution flicker

Post by cirimj82 »

Wondering if anyone has an answer to an issue with my XL-2. I use the Liberty to instruct and when its healthy I couldn't be happier. Students have a tendency to treat it a little rough and I am getting a flicker, usually a couple hundred feet after takeoff, of the FADEC Caution light. This is usually after a student moves the throttle forward quickly on takeoff or with a go around. Since this started, I have not done stalls or anything that requires moving the throttle forward quickly. There is usually a slight bit of engine roughness associated with this and it will go away pretty quickly (10 seconds). If I ask them to take it slow and count to 4 moving the throttle forward to full power, it runs great.

Slight recent history and a current squawk. I was having the FADEC caution light come on during runup and under high power. After running a diagnostic, I found that ECU-2 was throwing some 0's on the RPM's so Teledyne sent me a loaner ECU and it cleared it up. I purchased a new one, installed it and its airworthy again. Also, I am usually not getting EGT/CHT on cylinder 1 on my VM1000. I also got a ECU-1 loaner from Teledyne, installed it and that fixed it. I currently have that on order so, at the moment, I have my old one in. I don't think this is the problem because I've had this squawk for months. Also, one the rare occasion that I do have EGT/CHT 1, I noticed that my CHT on cylinder 4 is lower than the rest.

After reading the forums here, I've noticed that there have been a few injector problems associated with FADEC Caution lights. I am thinking this is the first thing to try and I intend to have my mechanic look at that ASAP. Since I do not have any other injectors, I will just have him clean them but I'm thinking I should probably replace at least the 4. Does anyone know where to order the injectors for this?

Any advice or help with this would certainly be appreciated.
rschutz
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Re: FADEC Caution flicker

Post by rschutz »

Hi,

have you tried reproducing this with the electrical fuel pump in ON. I had an engine driven fuel pump failure on my aircraft and the symptoms included stumbling during acceleration. Another symptom is fluctuation of fuel pressure.
I don't really think that this is the root cause but excluding the mechanical fuel pump by switching the electrical to ON should be an easy test.
GimpyPilot
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Re: FADEC Caution flicker

Post by GimpyPilot »

Hi,

I agree with your assessment that you've likely got a fuel injector issue in addition to your failed/failing ECU. Have you run the FADEC Phase 1 diagnostic and recorded the results? I would also try swapping injector locations to see if you can watch the symptom "move" from cylinder to cylinder. If you've got an injector issue that will show. If not, it's an ECU or something in the low voltage harness.

Cleaning these injectors requires some equipment and care. You'll need an injector solenoid and a DC power supply of something like 4 to 4.5 volts to cycle the injector open and closed. Without these, the injector will remain closed, and you won't be able to clean it effectively. Soak the injector in solvent first, as you would any standard injector. Then do it while cycling the injector on and off several times for about 30 seconds. (Be mindful of the input voltage. If you go much over about 4.5 volts, you'll kill the injector completely.)

Injectors are very expensive, but I think Aviall can still source them.

Also, see this thread...

http://www.xl2forum.com/viewtopic.php?p=8602#p8602

There's a DPU or an interconnect that could be at issue... but that can be isolated by moving injectors. (I haven't heard of this issue, but I found it here.)



-Michael
Last edited by GimpyPilot on Mon Apr 05, 2021 4:58 pm, edited 2 times in total.
N645XL
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Re: FADEC Caution flicker

Post by N645XL »

Something else to consider is the recent thread on the partially clogged fuel filter.
GimpyPilot
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Re: FADEC Caution flicker

Post by GimpyPilot »

N645XL wrote: Mon Apr 05, 2021 4:55 pm Something else to consider is the recent thread on the partially clogged fuel filter.
Great call! Start here, though that wouldn't necessarily explain the cylinder 4 temperature delta. Cylinder 4 *is* the forward one, so it might run slightly cooler depending on baffling.
cirimj82
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Re: FADEC Caution flicker

Post by cirimj82 »

Slight update to this, I’ve changed both fuel filters and also a gasket that was leaking on the #4 intake manifold right by the fuel injector. I’m still guessing it’s an injector. After Gimpypilot’s excellent description of how to clean it, I’m thinking I’ll need a little help and my mechanic is a little unsure as well. Getting it out and soaking it in the ultrasonic cleaner it easy but the injector solenoid and 4.5v power is what’s a little confusing.

2 questions, does anybody know someone around the Dallas area that knows how to do this? (If needed I would even take them out and fly commercial to meet someone) Or, if possible would anyone who does know how to do this be willing to take a phone call from me.

Thanks to any help in advance.

Mike
GimpyPilot
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Re: FADEC Caution flicker

Post by GimpyPilot »

cirimj82 wrote: Thu Apr 08, 2021 3:54 pm ...if possible would anyone who does know how to do this be willing to take a phone call from me.

Mike,

It's not as difficult as it sounds. I'll send you a message with my contact information so we can talk it through. Note that I am not an A&P/IA. I am a former XL-2 owner who dealt with this issue a couple of times, and learned the procedure from a Liberty factory technician.

-Michael
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