First Flight Engine Power Loss - FINDINGS

[N890GF]

I have since root caused my engine power loss on my first flight from last weekend (see thread).

TL;DR: Found debris in the injector(s) which caused my partial power loss - switched to loctite 565 instead of Permatex on the fuel pump inlet and cleaned the whole fuel system.

A bit of system background - I have an Andair Fuel Pump and Filter, Silverhawk Fuel Servo with a Precision Airmotive Fuel Spider and Nozzles. My Specific installation has the Andair fuel filter separated from the fuel pump by a tube, as a result I have an NPT to flared fitting on the fuel pump inlet. This fitting needs to be sealed of course, and when I originally installed the fitting, I used Permatex #3 aviation form-a-gasket. I came back a few days later to find a small drip of brown Permatex and a faint smell of fuel; I had a weep.

I took the pump out of the plane, removed the fitting and cleaned the threads out, removing all the old sealant. I applied some new Loctite 565 instead (per recommendations on these forums for when Permatex doesn't work), and that solved my fuel leak. Maybe my Permatex was old, not sure why it didn't seal.

A few weeks later (early Jan 2026), I did some ground runs in preparation for the first flight. The engine ran rough, i couldnt get the mixture right, it rose >300RPM when going to idle-cutoff, EGTs were all over the place, and black smoke was observed from the exhaust. I removed the injectors and found some debris in the #4 restrictor. I cleaned it out, and the engine ran wonderfully. I did all my ground runs up to full power, and all the tests passed after that.

After my first flight engine issue I immediately suspected debris in the injectors. Partial power loss, 1, 2, 3 EGTs dropping suddenly (I suspected overly rich fuel flow cooling the EGTs and causing poor combustion), and black smoke see by my ground observer, seemed like an exact replica of my initial ground run woes. Well I did indeed find debris in the #4 restrictor. It looked like some curved, dried Permatex from the pump threads that made its way to the engine.

I have since cleaned out and flushed the whole system, re-cleaned the threads on the fuel pump (extra careful this time), and have run the system all the way to the nozzles showing even flow from all four nozzles. Engine ran great after putting everything back together, all EGTs were even, and CHTs similarly were all within normal ranges (for the 3 minutes I ran the engine).

I will hopefully not be discussing my next flight due to it being a boring, routine flight.

 

[riseric]

Glad for you for finding the probable cause.
Hoping in fact to hear from you discussing your next boring and routine flight !!

 

[rapid_ascent]

George, Since you weren't specific about what you cleaned in the fuel system. I thought I would mention that there is a filter screen inside the servo at the fuel input. I'm not sure if you are aware or not. It might be a good idea to check and clean that filter as well.

 

[rv8ch]

I will hopefully not be discussing my next flight due to it being a boring, routine flight.

That's what we all hope! Just in case, I'd ensure you do the check Ray mentioned, and spend the first hour or so over the airport, ready for a repeat. Getting gunk like this completely out of the fuel system is not easy. It's similar to when people unknowingly use teflon tape in the fuel system, which is evil. The problems can come way down the road. Good luck, George!

 

[jakej]

I have since root caused my engine power loss on my first flight from last weekend (see thread).

TL;DR: Found debris in the injector(s) which caused my partial power loss - switched to loctite 565 instead of Permatex on the fuel pump inlet and cleaned the whole fuel system.

A bit of system background - I have an Andair Fuel Pump and Filter, Silverhawk Fuel Servo with a Precision Airmotive Fuel Spider and Nozzles. My Specific installation has the Andair fuel filter separated from the fuel pump by a tube, as a result I have an NPT to flared fitting on the fuel pump inlet. This fitting needs to be sealed of course, and when I originally installed the fitting, I used Permatex #3 aviation form-a-gasket. I came back a few days later to find a small drip of brown Permatex and a faint smell of fuel; I had a weep.

I took the pump out of the plane, removed the fitting and cleaned the threads out, removing all the old sealant. I applied some new Loctite 565 instead (per recommendations on these forums for when Permatex doesn't work), and that solved my fuel leak. Maybe my Permatex was old, not sure why it didn't seal.

A few weeks later (early Jan 2026), I did some ground runs in preparation for the first flight. The engine ran rough, i couldnt get the mixture right, it rose >300RPM when going to idle-cutoff, EGTs were all over the place, and black smoke was observed from the exhaust. I removed the injectors and found some debris in the #4 restrictor. I cleaned it out, and the engine ran wonderfully. I did all my ground runs up to full power, and all the tests passed after that.

After my first flight engine issue I immediately suspected debris in the injectors. Partial power loss, 1, 2, 3 EGTs dropping suddenly (I suspected overly rich fuel flow cooling the EGTs and causing poor combustion), and black smoke see by my ground observer, seemed like an exact replica of my initial ground run woes. Well I did indeed find debris in the #4 restrictor. It looked like some curved, dried Permatex from the pump threads that made its way to the engine.

I have since cleaned out and flushed the whole system, re-cleaned the threads on the fuel pump (extra careful this time), and have run the system all the way to the nozzles showing even flow from all four nozzles. Engine ran great after putting everything back together, all EGTs were even, and CHTs similarly were all within normal ranges (for the 3 minutes I ran the engine).

I will hopefully not be discussing my next flight due to it being a boring, routine flight.

I have the same pump & fuel system as you have. Very similar issue except -
After some upper air work for my biannual renewal we entered the circuit for a ‘touch & go’ , executed a late go around (40 deg flap - long story, but safe) & applied full power for climb out. Then it ran real rough (seemed like an overly rich mixture event) & wasn’t climbing well, managed to clear a fence at 60 knots ( impossible to stop before it ) , decided to pull the mixture back a little & engine seemed to have more power, instructor then reduced throttle a bit too ( not a word was said during this time) resulting in more performance. I was preparing to land in the clearing ahead however with the extra power I was able to climb slowly & raise the flaps. Then continued the circuit for the landing - passed my check.
Same cause as yours- an injector was partially blocked which causes the all the normal fuel flow to be fed to the other 3 injectors resulting in an ‘over rich’ flow followed by a big reduction of expected power on the go around.
Afterwards I talked to my engine guy & reducing mixture sure helps in this situation- who’d have known?
That scenario, re blocked, partially or otherwise, injector/s, was never mentioned or talked about in my 54 years of flying (12yrs behind my own IO-360) . Maybe there should be some debate on this issue?
Ps - I was lucky as I was already in a setup basically for a forced landing & having a reasonable landing area on the other side of the fence- which I was prepared to use until I / we regained some power & climb rate to enable completion of the circuit. Hopefully this scenario is of use to anyone who may experience a similar situation- at least think about it and decide what you may do in the same situation.

 

[Dugaru]

That scenario, re blocked, partially or otherwise, injector/s, was never mentioned or talked about in my 54 years of flying (12yrs behind my own IO-360) . Maybe there should be some debate on this issue?

Great point. I think most of us (myself included) have been WAY undertrained when it comes to partial power loss, which I suspect is more common than total power loss. When it happened to me years ago in a certified airplane shortly after takeoff, my only thought was “it’s still running and it’s able to maintain altitude, so I’m not touching anything until after I land.” No idea, to this day, if that was the best move. It later dawned on me that unlike total power loss, there was no procedure to deal with it that had been drilled into my head.

 

[airguy]

I had this happen to me once, caught a piece of debris in my #3 injector (before I installed SDS) when my plane came out of paint. I had opened the fuel lines while the plane was in the paint shop for some simultaneous work - I thought I was extra careful to keep it all clean - yeah right. After paint was done, I started it, ran it up on the ramp outside the shop and all was good. Taxied to the end of the runway, ran it up again, all was good. Proceeded with the departure and perhaps 1 full second after application of full power the engine sagged and started shaking like a wet dog. I immediately pulled power and turned off at the next taxiway and went back to the paint shop ramp. Did some more engine up/downs and my instrumentation strongly suggested #3, so I pulled that injector and sure enough, there it was. My runups prior to departure did not place enough load on the engine to get full fuel flow (constant speed prop - never came off the fine pitch stop) - but the takeoff roll did - and something dislodged and moved to the injectors.

 

[airguy]

I will hopefully not be discussing my next flight due to it being a boring, routine flight.

By all means - now we WANT to hear about that next boring flight!

 

[Gino230]

This happened to my brother and I when I was flying his Twin Commanche years ago. It turned out to be rust from the inside of a newly installed AN fitting for the fuel flow transducer. We went haywire trying to find the source of the debris, it wasn't until someone stuck a magnet into the baby bottles we were using for the injector flow test that we began to have a clue.

It was very strange, when I went to pull power back to feather the #2 engine, RPM actually increased- so I left it there and landed and I never really knew why- I just knew it was running (barely) and landed. Prop stopped on the rollout.

As I mentioned in the other thread- having an engine monitor displaying all 4 EGTs can be a lifesaver- you will see the clogged one spike and then drop as the cylinder loses power. If you're at a reduced power setting you'll know right away that you have a problem- instead of when you push it up for go-around like I did.

 

[lr172]

I have since root caused my engine power loss on my first flight from last weekend (see thread).

TL;DR: Found debris in the injector(s) which caused my partial power loss - switched to loctite 565 instead of Permatex on the fuel pump inlet and cleaned the whole fuel system.

A bit of system background - I have an Andair Fuel Pump and Filter, Silverhawk Fuel Servo with a Precision Airmotive Fuel Spider and Nozzles. My Specific installation has the Andair fuel filter separated from the fuel pump by a tube, as a result I have an NPT to flared fitting on the fuel pump inlet. This fitting needs to be sealed of course, and when I originally installed the fitting, I used Permatex #3 aviation form-a-gasket. I came back a few days later to find a small drip of brown Permatex and a faint smell of fuel; I had a weep.

I took the pump out of the plane, removed the fitting and cleaned the threads out, removing all the old sealant. I applied some new Loctite 565 instead (per recommendations on these forums for when Permatex doesn't work), and that solved my fuel leak. Maybe my Permatex was old, not sure why it didn't seal.

A few weeks later (early Jan 2026), I did some ground runs in preparation for the first flight. The engine ran rough, i couldnt get the mixture right, it rose >300RPM when going to idle-cutoff, EGTs were all over the place, and black smoke was observed from the exhaust. I removed the injectors and found some debris in the #4 restrictor. I cleaned it out, and the engine ran wonderfully. I did all my ground runs up to full power, and all the tests passed after that.

After my first flight engine issue I immediately suspected debris in the injectors. Partial power loss, 1, 2, 3 EGTs dropping suddenly (I suspected overly rich fuel flow cooling the EGTs and causing poor combustion), and black smoke see by my ground observer, seemed like an exact replica of my initial ground run woes. Well I did indeed find debris in the #4 restrictor. It looked like some curved, dried Permatex from the pump threads that made its way to the engine.

I have since cleaned out and flushed the whole system, re-cleaned the threads on the fuel pump (extra careful this time), and have run the system all the way to the nozzles showing even flow from all four nozzles. Engine ran great after putting everything back together, all EGTs were even, and CHTs similarly were all within normal ranges (for the 3 minutes I ran the engine).

I will hopefully not be discussing my next flight due to it being a boring, routine flight.

Most debris from upstream of the servo should get caught by the finger strainer in the servo (IIRC, 30-40 micron) and not make it to the injectors. Yes, it does happen ocassionally, but most gets caught there. If you are confident that the debris is coming from upstream sources, you really need to get in the servo and find out why the filter is not doing its job. Several possibilities and they have a bypass mechanism. Brand new engine makes me think the debris was in lines downstream of servo.

 

[DanH]

When it happened to me years ago in a certified airplane shortly after takeoff, my only thought was “it’s still running and it’s able to maintain altitude, so I’m not touching anything until after I land.” No idea, to this day, if that was the best move.

Did you land safely? If so, it was the best move.

George, Since you weren't specific about what you cleaned in the fuel system. I thought I would mention that there is a filter screen inside the servo at the fuel input. I'm not sure if you are aware or not. It might be a good idea to check and clean that filter as well.

Agree. In theory, contamination prior to the servo inlet should not cause nozzle blockage unless the debris is (1) liquid enough to flow through a very fine screen, or (2) so much garbage has built up on the inlet screen that it has compressed its spring, allowing the flow to bypass the screen. When that happens you get a lot of garbage in the nozzles, but it should be rare.

It is far more likely that the contamination in the nozzles had a source in the servo or downstream of it.

BTW, Precision specifies a 32 micron filter prior to the servo, although they do say it may be upstream of the engine driven pump. Note 32 micron is 0.00126". The nozzles are nominally 0.028 or 0.024".

Edit; Hey, I see Larry had the same thought.

 

[Dugaru]

Did you land safely? If so, it was the best move.

I did, so I’m not complaining. But I do truly wonder whether troubleshooting a problem like that in the air increases or decreases the odds of a good outcome.

 

[lr172]

I did, so I’m not complaining. But I do truly wonder whether troubleshooting a problem like that in the air increases or decreases the odds of a good outcome.

I think a lot has to do with your knowledge level and the severity of the symptoms. IMHO, if you cannot positively identify the cause in a relatively short period of time (seconds), step one is plan immediate landing and further diagnos enroute if situation allows. Chances are good that the average joe will not correctly diagnos and run a risk that initial symptoms were just the first step in a cascade of symptoms resulting in complete engine loss.

 

[lr172]

I think a lot has to do with your knowledge level and the severity of the symptoms. IMHO, if you cannot positively identify the cause in a relatively short period of time (seconds), step one is plan immediate landing and further diagnos enroute if situation allows. Chances are good that the average joe will not correctly diagnos and run a risk that initial symptoms were just the first step in a cascade of symptoms resulting in complete engine loss.

I had fuel contamination problems appear a minute or so into a flight (8 miles from home airport). TO was normal. The problems were mild, but abnormal, and making decent power. I could not definitively diagnos in 5 seconds, though pretty confident it was fuel delivery, so made an immediate turn around and by the time I was on the ground, I could not produce enough power to taxi and had to push the plane part of the way. I had held my altitude and busted the Bravo to be sure I could glide in. I am pretty good at diagnostics and have diagnosed other issuies in the air, but still chose immediate turn around here. Had I continued instead of returning, I would have been dead sticking in a parking lot (densely populated terrain).

Self diagnosing in the air is a very dangerous game and suggest the majority of pilots avoid the temptation. Put it on the ground and figure it out there.

 

[JonJay]

BTW, Precision specifies a 32 micron filter prior to the servo, although they do say it may be upstream of the engine driven pump. Note 32 micron is 0.00126". The nozzles are nominally 0.028 or 0.024".

I have the same set up as the OP.
Vans standard for injected engines, some twenty years ago at least, was the AFP pump and filter. They sold a kit with everything you needed including the “doghouse”. The Silverhawk was a very common servo.
I should identify the filter. AFP’s finest filter is a 40 micron, largest is 125. Both much finer than an injector.
These are upstream obviously.

Next time I speak with Don I’ll ask him for his thoughts.

As far as the issue here, I am with you and Larry. Having trouble seeing how an injector gets contaminated downstream of the last chance filter unless it’s totally clogged. A bit of sealant isn’t going to do that. If it is clogged and bypassed the servo needs to be sent in for service.