Engine failure in flight Jan.31

[Shiroyuki]

This happened quite a while ago but it's only now that I'm willing to bring it up.

I was flying my 77 J enroute from CYTZ to my home airport CYXL on Jan.31 2025. It was a 650nm flight over mostly remote part of Northern Ontario. Roughly three and half hour into the flight, about one hour from reaching my destination, in the vicinity of Nipigon Ontario, at a cruising altitude of 5500ft, the engine started to sputter. I immediately turned boost pump on and then my engine quit completely.

I acted upon the situation as everyone would, I was lucky that there is a highway right below me, and I quickly turned my plane gliding alone the highway looking for a suitable landing spot. Then I tried to trouble shoot the problem, and declared mayday on both Center frequency (but I'm on the edge of their reception) and 126.7.

Oil, fuel pressure were in the green. I had plenty of fuel. Propeller was windmilling, there is no oil spraying everywhere or any catastrophic failure. I even had fuel flow, though only 3-6 gph. But I had no power. Engine monitor show all four cylinder cold on EGT. I tried both mag, didn't switch tank because I already ran one dry, and determined I cannot bring the engine back. The subsequent landing on the highway is uneventful. Clipped two small roadsign during the landing roll, but I'm fine and the plane is now being repair in Toronto, after a temporary repair was carried out in the field and got a ferry permit from TC.

The landing happened just before sunset, temperature at landing was -20c. If it would've happened ten minutes prior or later, I would've end up landing on a frozen lake. That was the only highway along my route for almost 300 miles. I think I got lucky here.

After landing, I checked the oil, sitting exactly at 6 qts. I spun the prop and noticed smooth movement with no issue, and normal compression in all four cylinder. I then checked my fuel tank and I could see plenty of gas. The only thing abnormal, that I noticed, was when I turn on the boost pump there is a strong smell of fuel. During departure out of CYTZ, when I turn on the fuel point in the takeoff check, I also smelled a whif of gas but I did not thought to much about it.

Shortly after, police, fire and ambulance arrived, though I do not require fire and ambulance (luckily I don't need to pay for ambulance). A snow plow came, plowed out a side road and move my plane there, where it sat for two month getting the wing patched up and a ferry permit issued from TC.

A local float plane company sent a few mechanics and inspected the engine. They found the fuel line out of the engine driven pump to be loose at the connector, causing a very significant fuel leak. The reason why it is loose, according to the mechanics, is likely because the fuel line with fire sleeve over it was rubbing against the firewall, loosening it over time. Both mags are firing properly and sparks are produced on all 8 plugs.

I'm not sure how much I believe this theory. Since during the flight, I ran the right tank dry, and my fuel accumulator read exactly 32 gallon used. The fuel flow transducer is located after the leak, so if there is any leak, I'd ran out of fuel before my fuel accumulator reaches 32. The mechanic in Toronto that usually worked on my plane said it might be due to some kind of icing issue inside the injector servo or controller or something like that, and the float plane mechanic did agree that it's also a possibility. He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks.

They removed the fire sleeve on that fuel line, reconnected the hose properly and ran the engine up, and it ran fine. So we eventually flew it out to toronto for permanant repair on the wing with a fueling stop in Thunder bay.

Now the plane is sitting in my mechanic hangar in Toronto, I've asked my mechanic to thoroughly inspect the engine again, which I asked him to do last time when I was dealing with the prop governer fuel leak isssue. I'm really not sure how do I trust this plane again. For the past year that I've owned this airplane, I was always on the way of fixing something. The engine was looked into at least twice under my request to make sure the pervious owner's mechanic who installed the engine did not make any more mistake that's not yet discovered.

Just sharing my experience here. I guess from now on I will use 1% alcohol added into the fuel to prevent icing.

I'd love to hear everyone's thought's on this. 

[toto]

34 minutes ago, Shiroyuki said:

This happened quite a while ago but it's only now that I'm willing to bring it up.

I was flying my 77 J enroute from CYTZ to my home airport CYXL on Jan.31 2025. It was a 650nm flight over mostly remote part of Northern Ontario. Roughly three and half hour into the flight, about one hour from reaching my destination, in the vicinity of Nipigon Ontario, at a cruising altitude of 5500ft, the engine started to sputter. I immediately turned boost pump on and then my engine quit completely.

I acted upon the situation as everyone would, I was lucky that there is a highway right below me, and I quickly turned my plane gliding alone the highway looking for a suitable landing spot. Then I tried to trouble shoot the problem, and declared mayday on both Center frequency (but I'm on the edge of their reception) and 126.7.

Oil, fuel pressure were in the green. I had plenty of fuel. Propeller was windmilling, there is no oil spraying everywhere or any catastrophic failure. I even had fuel flow, though only 3-6 gph. But I had no power. Engine monitor show all four cylinder cold on EGT. I tried both mag, didn't switch tank because I already ran one dry, and determined I cannot bring the engine back. The subsequent landing on the highway is uneventful. Clipped two small roadsign during the landing roll, but I'm fine and the plane is now being repair in Toronto, after a temporary repair was carried out in the field and got a ferry permit from TC.

The landing happened just before sunset, temperature at landing was -20c. If it would've happened ten minutes prior or later, I would've end up landing on a frozen lake. That was the only highway along my route for almost 300 miles. I think I got lucky here.

After landing, I checked the oil, sitting exactly at 6 qts. I spun the prop and noticed smooth movement with no issue, and normal compression in all four cylinder. I then checked my fuel tank and I could see plenty of gas. The only thing abnormal, that I noticed, was when I turn on the boost pump there is a strong smell of fuel. During departure out of CYTZ, when I turn on the fuel point in the takeoff check, I also smelled a whif of gas but I did not thought to much about it.

Shortly after, police, fire and ambulance arrived, though I do not require fire and ambulance (luckily I don't need to pay for ambulance). A snow plow came, plowed out a side road and move my plane there, where it sat for two month getting the wing patched up and a ferry permit issued from TC.

A local float plane company sent a few mechanics and inspected the engine. They found the fuel line out of the engine driven pump to be loose at the connector, causing a very significant fuel leak. The reason why it is loose, according to the mechanics, is likely because the fuel line with fire sleeve over it was rubbing against the firewall, loosening it over time. Both mags are firing properly and sparks are produced on all 8 plugs.

I'm not sure how much I believe this theory. Since during the flight, I ran the right tank dry, and my fuel accumulator read exactly 32 gallon used. The fuel flow transducer is located after the leak, so if there is any leak, I'd ran out of fuel before my fuel accumulator reaches 32. The mechanic in Toronto that usually worked on my plane said it might be due to some kind of icing issue inside the injector servo or controller or something like that, and the float plane mechanic did agree that it's also a possibility. He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks.

They removed the fire sleeve on that fuel line, reconnected the hose properly and ran the engine up, and it ran fine. So we eventually flew it out to toronto for permanant repair on the wing with a fueling stop in Thunder bay.

Now the plane is sitting in my mechanic hangar in Toronto, I've asked my mechanic to thoroughly inspect the engine again, which I asked him to do last time when I was dealing with the prop governer fuel leak isssue. I'm really not sure how do I trust this plane again. For the past year that I've owned this airplane, I was always on the way of fixing something. The engine was looked into at least twice under my request to make sure the pervious owner's mechanic who installed the engine did not make any more mistake that's not yet discovered.

Just sharing my experience here. I guess from now on I will use 1% alcohol added into the fuel to prevent icing.

I'd love to hear everyone's thought's on this. 

Wow, thank you for sharing. Glad to hear you’re okay and the airplane is fixable. I’ll leave the mechanical diagnosis to the experts, but from my perspective it sounds like you handled things very professionally both during and after the event.

A dead stick landing on a narrow road after a complete engine failure is not something any of us wants to happen, but this is about as positive an outcome as we can hope for. 

This reminds me of the recent experience that @AME LLC had:

 

[Ragsf15e]

2 hours ago, Shiroyuki said:

This happened quite a while ago but it's only now that I'm willing to bring it up.

I was flying my 77 J enroute from CYTZ to my home airport CYXL on Jan.31 2025. It was a 650nm flight over mostly remote part of Northern Ontario. Roughly three and half hour into the flight, about one hour from reaching my destination, in the vicinity of Nipigon Ontario, at a cruising altitude of 5500ft, the engine started to sputter. I immediately turned boost pump on and then my engine quit completely.

I acted upon the situation as everyone would, I was lucky that there is a highway right below me, and I quickly turned my plane gliding alone the highway looking for a suitable landing spot. Then I tried to trouble shoot the problem, and declared mayday on both Center frequency (but I'm on the edge of their reception) and 126.7.

Oil, fuel pressure were in the green. I had plenty of fuel. Propeller was windmilling, there is no oil spraying everywhere or any catastrophic failure. I even had fuel flow, though only 3-6 gph. But I had no power. Engine monitor show all four cylinder cold on EGT. I tried both mag, didn't switch tank because I already ran one dry, and determined I cannot bring the engine back. The subsequent landing on the highway is uneventful. Clipped two small roadsign during the landing roll, but I'm fine and the plane is now being repair in Toronto, after a temporary repair was carried out in the field and got a ferry permit from TC.

The landing happened just before sunset, temperature at landing was -20c. If it would've happened ten minutes prior or later, I would've end up landing on a frozen lake. That was the only highway along my route for almost 300 miles. I think I got lucky here.

After landing, I checked the oil, sitting exactly at 6 qts. I spun the prop and noticed smooth movement with no issue, and normal compression in all four cylinder. I then checked my fuel tank and I could see plenty of gas. The only thing abnormal, that I noticed, was when I turn on the boost pump there is a strong smell of fuel. During departure out of CYTZ, when I turn on the fuel point in the takeoff check, I also smelled a whif of gas but I did not thought to much about it.

Shortly after, police, fire and ambulance arrived, though I do not require fire and ambulance (luckily I don't need to pay for ambulance). A snow plow came, plowed out a side road and move my plane there, where it sat for two month getting the wing patched up and a ferry permit issued from TC.

A local float plane company sent a few mechanics and inspected the engine. They found the fuel line out of the engine driven pump to be loose at the connector, causing a very significant fuel leak. The reason why it is loose, according to the mechanics, is likely because the fuel line with fire sleeve over it was rubbing against the firewall, loosening it over time. Both mags are firing properly and sparks are produced on all 8 plugs.

I'm not sure how much I believe this theory. Since during the flight, I ran the right tank dry, and my fuel accumulator read exactly 32 gallon used. The fuel flow transducer is located after the leak, so if there is any leak, I'd ran out of fuel before my fuel accumulator reaches 32. The mechanic in Toronto that usually worked on my plane said it might be due to some kind of icing issue inside the injector servo or controller or something like that, and the float plane mechanic did agree that it's also a possibility. He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks.

They removed the fire sleeve on that fuel line, reconnected the hose properly and ran the engine up, and it ran fine. So we eventually flew it out to toronto for permanant repair on the wing with a fueling stop in Thunder bay.

Now the plane is sitting in my mechanic hangar in Toronto, I've asked my mechanic to thoroughly inspect the engine again, which I asked him to do last time when I was dealing with the prop governer fuel leak isssue. I'm really not sure how do I trust this plane again. For the past year that I've owned this airplane, I was always on the way of fixing something. The engine was looked into at least twice under my request to make sure the pervious owner's mechanic who installed the engine did not make any more mistake that's not yet discovered.

Just sharing my experience here. I guess from now on I will use 1% alcohol added into the fuel to prevent icing.

I'd love to hear everyone's thought's on this. 

Holy S$!T!! Nice landing!  That was not a forgiving road with the snow and posts on the sides!  Well done.  Also really glad it was on a road because anywhere else at -20c is an immediate survival situation and you better have good gear accessible!

If it was -20c on the ground, what was the temp at cruise (re alcohol in fuel)?

if the fuel line was pouring enough fuel out to kill the engine, wouldn’t the entire belly of the plane be blue ?

[DCarlton]

I’m not a mechanic but I discovered recently during a visual inspection that the Mooney fuel line service bulletin issued decades ago was never accomplished on my airplane.  It was mandatory and immediate for airplanes flown in icing conditions.  After approx 20 years of ownership,  I downloaded all the ADs and SBs from the Mooney web site and found this one non-compliant.  We’re addressing it now.  Not finding root cause of an engine failure can be very troubling.  

[MikeOH]

1 minute ago, DCarlton said:

I’m not a mechanic but I discovered recently during a visual inspection that the Mooney fuel line service bulletin issued decades ago was never accomplished on my airplane.  It was mandatory and immediate for airplanes flown in icing conditions.  I had downloaded all the SBs from the Mooney web site and found this one non-compliant.  We’re addressing it now.  Not finding root cause of an engine failure can be very troubling.  

Hmm, what is the S/B number, please?  I want to check my plane for compliance.

[DCarlton]

4 minutes ago, MikeOH said:

Hmm, what is the S/B number, please?  I want to check my plane for compliance.

https://mooney.com/wp-content/uploads/2020/12/SBM20-166.pdf

[MikeOH]

3 minutes ago, DCarlton said:

https://mooney.com/wp-content/uploads/2020/12/SBM20-166.pdf

Thank you!

Doesn't look like it applies by S/N to my 1970 M20F.

[DCarlton]

2 minutes ago, MikeOH said:

Thank you!

Doesn't look like it applies by S/N to my 1970 M20F.

I would still take a look.  Guessing the fuel line routing could have been changed if the engine was overhauled or the fuel line was replaced particularly if someone bought a fuel line that was a little too long.  

[MikeOH]

17 minutes ago, DCarlton said:

I would still take a look.  Guessing the fuel line routing could have been changed if the engine was overhauled or the fuel line was replaced particularly if someone bought a fuel line that was a little too long.  

Good point!  I'll take a look.

[OR75]

just curious why you wanted to run one tank dry for a 650nm route.

[skykrawler]

"I immediately turned boost pump on and then my engine quit completely."

Hmm,  the rule some live by is:  If a switch is moved and bad things happen, put it back.

"He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks."

Was the gascolator 'sumped?'   A regular fuel cup can be used to sample there and it is the lowest point.

The fuel pressure transducer on J models takes pressure from an output line of the fuel servo.  The boost pump pushes through that hose and fitting.   The mechanical pump on the engine sucks though that hose.   If the B nut was loose it could have been sucking air enough for the engine to not run....but you say you had pressure in the green.

Seems like you must accept the evidence at hand (loose fuel hose). 

The firewall fitting bulletin seems to apply to E and F models. 

[LANCECASPER]

5 hours ago, OR75 said:

just curious why you wanted to run one tank dry for a 650nm route.

I can think of a few reasons why I wouldn't want to do that.

1 Why would you want to be out of balance that far with all of the fuel on one side?

2 If the engine runs rough on the fuel from one side you could suspect water in that side and you would know that after your first tank change over. If the good side is now empty and it starts running rough you don't have any options other than perhaps an off field landing

3 There have been instances on Mooneyspace where the pilot said that the fuel selector was very difficult or impossible to turn. If I have stayed on one tank and run it dry and now I am unable to select the other tank I'm going to be landing wherever I can in the next couple minutes. If I have been switching tanks every 30-60 minutes, I know the selector works and even if it malfunctions at that point at least I have time to find a place to land by staying on the tank I am on. 

 

[Hank]

6 hours ago, OR75 said:

just curious why you wanted to run one tank dry for a 650nm route.

 

46 minutes ago, LANCECASPER said:

I can think of a few reasons why I wouldn't want to do that.

1 Why would you want to be out of balance that far with all of the fuel on one side?

I change tanks every hour, but on a long flight will often extend the 2nd hour on the takeoff tank to over 90 minutes, then make a final switch. That prevents me arriving at my destination with 12-15 gallons split between both tanks.

Then again, my C only carries 52 gallons, but that's good for almost 6 hours; I prefer less than 4:30 just because I like to stand up around then.

For example, takeoff and climb, L tank, one hour; R tank one hour; L tank 90-100 minutes, or until sputter for a really long leg; leaving R tank with 1 hour plus Golden Hour reserve.

Remember, it's not just distance that determines flight time and fuel requirements, it's the winds aloft. I've recently made several trips to Houston, 505 nm; my flights were all 6000-8000 msl, same power settings, but flight times varied from 3.0 to 4.6 hours.

[Ragsf15e]

Does anyone really believe running the other tank dry has anything to do with this?  There are a few instances I’ve used the technique as well and certainly there are considerations, but I think we’re going off on a tangent here.

[201er]

15 hours ago, Shiroyuki said:

Oil, fuel pressure were in the green. I had plenty of fuel. Propeller was windmilling, there is no oil spraying everywhere or any catastrophic failure. I even had fuel flow, though only 3-6 gph. But I had no power. Engine monitor show all four cylinder cold on EGT. I tried both mag, didn't switch tank because I already ran one dry, and determined I cannot bring the engine back. The subsequent landing on the highway is uneventful.

Did you try cycling the mixture? It could be that the fuel leak wasn't starving the engine entirely of fuel but enough to make it unusable at that mixture setting.

[Shiroyuki]

7 hours ago, OR75 said:

just curious why you wanted to run one tank dry for a 650nm route.

 

2 hours ago, skykrawler said:

"I immediately turned boost pump on and then my engine quit completely."

Hmm,  the rule some live by is:  If a switch is moved and bad things happen, put it back.

"He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks."

Was the gascolator 'sumped?'   A regular fuel cup can be used to sample there and it is the lowest point.

The fuel pressure transducer on J models takes pressure from an output line of the fuel servo.  The boost pump pushes through that hose and fitting.   The mechanical pump on the engine sucks though that hose.   If the B nut was loose it could have been sucking air enough for the engine to not run....but you say you had pressure in the green.

Seems like you must accept the evidence at hand (loose fuel hose). 

The firewall fitting bulletin seems to apply to E and F models. 

650nm with a head wind is streching the range. When I arrived I would've only have about 20 gallon left, and closest alternate would've been another hour away. Remember this is not the plain of US with airport every 10 miles, this is in the middle of nowhere deep in the canadian shield. There isn't even a human settlement for at least 100km. I want all my fuel in one tank if i have few left. That has nothing to do with this engine failure, as I took off on left tank, switch to right tank once leveled off in cruise, and switched back to left tank.

[Shiroyuki]

3 hours ago, skykrawler said:

"I immediately turned boost pump on and then my engine quit completely."

Hmm,  the rule some live by is:  If a switch is moved and bad things happen, put it back.

"He says I should not loose power completely if I still have fuel flow and green fuel pressure. To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new. It was noted the boost pump was functioning properly providing proper pressure with no leaks."

Was the gascolator 'sumped?'   A regular fuel cup can be used to sample there and it is the lowest point.

The fuel pressure transducer on J models takes pressure from an output line of the fuel servo.  The boost pump pushes through that hose and fitting.   The mechanical pump on the engine sucks though that hose.   If the B nut was loose it could have been sucking air enough for the engine to not run....but you say you had pressure in the green.

Seems like you must accept the evidence at hand (loose fuel hose). 

The firewall fitting bulletin seems to apply to E and F models. 

 

10 minutes ago, 201er said:

Did you try cycling the mixture? It could be that the fuel leak wasn't starving the engine entirely of fuel but enough to make it unusable at that mixture setting.

I did cycle the  mixture and tried boost pump on and off, and different throttle setting, and no luck. The mechanic says maybe the extra pressure from boost pump loosend the line more causing more leak. But I don't know how much I buy into this theory. He did mention it was a very significant leak though...

I did sump my gascolator via pulling the ring on the floor. But I only sump the gascolator at the begining of a day, not after every refueling like the wing sump... And that was the second flight of the day.

To add, the engine have about 120 hours since overhaul. But the engine itself seems find.. I don't think that is related either. A bad installation is likely the culprit.

Edited April 20 by Shiroyuki

[MB65E]

I would re-torque all of the fuel and oil lines. B-nuts don’t back off unless they are previously cracked or under torqued. 
I also make sure that any aircraft I work on have Steel fittings on BOTH sides of the engine driven fuel pump. The vibration and load on the fittings work hardens the aluminum fittings. I’ve seen them crack. 

Also if the idle mixture adjustment quits having a rise, or if adjusting the idle mixture doesn’t respond the fuel servo is on its last leg and needs to be overhauled. 
I’ve had one emergency landing due to this and have found 2 other clients with bad fuel servos after noticing the suspect idle mixture settings. 
 

Nice work getting the airplane down safely. 

-Matt

[OR75]

1 hour ago, Shiroyuki said:

 

650nm with a head wind is streching the range. When I arrived I would've only have about 20 gallon left, and closest alternate would've been another hour away. Remember this is not the plain of US with airport every 10 miles, this is in the middle of nowhere deep in the canadian shield. There isn't even a human settlement for at least 100km. I want all my fuel in one tank if i have few left. That has nothing to do with this engine failure, as I took off on left tank, switch to right tank once leveled off in cruise, and switched back to left tank.

I am not saying it has something to do with the engine failure. Likely it does not.    

[OR75]

3 hours ago, LANCECASPER said:

I can think of a few reasons why I wouldn't want to do that.

1 Why would you want to be out of balance that far with all of the fuel on one side?

2 If the engine runs rough on the fuel from one side you could suspect water in that side and you would know that after your first tank change over. If the good side is now empty and it starts running rough you don't have any options other than perhaps an off field landing

3 There have been instances on Mooneyspace where the pilot said that the fuel selector was very difficult or impossible to turn. If I have stayed on one tank and run it dry and now I am unable to select the other tank I'm going to be landing wherever I can in the next couple minutes. If I have been switching tanks every 30-60 minutes, I know the selector works and even if it malfunctions at that point at least I have time to find a place to land by staying on the tank I am on. 

 

agree on all 3 points.

with windmilling and fuel flowing, an engine is easy to start. The selector needs to cooperate at all time.

[PT20J]

Nice job handling the emergency. 5500 feet isn't all that high -- probably less AGL -- and you made the Mayday call, found a landing spot and did all the troubleshooting you could.

The B nut on the fuel pump was probably loose at takeoff and vibration caused it to become a lot looser in flight. Since it was on the output of the fuel pump it could easily reduce fuel flow. The pump will attempt to maintain fuel pressure by increasing the flow, but most is going out the leak and not to the servo. The 3-6 gph you saw at cruise throttle probably drove the mixture too far LOP for combustion.

I had that same B nut come loose on my 1978 J. Fortunately, it was only slightly loose and I noticed it when returning to the plane after a short stop because gas was dripping on the nose tire. I was lucky because I had planned a long flight with my wife the next day over inhospitable terrain.  I tightened the fitting and never had another problem. I would expect that yours will be fine.

[Fritz1]

excellent job getting the bird down, the previous threads have covered the mechanicals, in order to regain confidence in the bird the best thing for you to do is to go over every possible source of failure together with your mechanic, check and/or retorque all the lines and fittings, check and/or overhaul fuel servo. Thereafter slowly reacquaint yourself with the airplane, ground run, traffic patterns, widen the circle. You may never find out what really happened, ice may have formed somewhere in the fuel system at least contributing to the event. No engine runs as well as the one you have fixed yourself. Fly safe!

 

 

 

 

[EricJ]

9 hours ago, Shiroyuki said:

 

I did cycle the  mixture and tried boost pump on and off, and different throttle setting, and no luck. The mechanic says maybe the extra pressure from boost pump loosend the line more causing more leak. But I don't know how much I buy into this theory. He did mention it was a very significant leak though...

I did sump my gascolator via pulling the ring on the floor. But I only sump the gascolator at the begining of a day, not after every refueling like the wing sump... And that was the second flight of the day.

To add, the engine have about 120 hours since overhaul. But the engine itself seems find.. I don't think that is related either. A bad installation is likely the culprit.

Sound like you did all the right things.   Had you been cruising with the ram air open by any chance?    Was there any moisture in the air where you were cruising?   The fuel servo is sensitive to what happens with the ram tubes, and if the ram air is open and there's any moisture in the air I'm guessing it's possible either one or more ram tubes iced over or moisture was ingested into a ram tube and froze inside the servo.   There's all kinds of crazy stuff can happen when then servo isn't happy, including failing (I've been there, too).   It would also explain why everything was fine afterward.   That's just speculation on my part, but it might have been something crazy like that.

Edit:  BTW, nicely done and I'm glad it came out well and you're getting it sorted out.

 

[DCarlton]

7 hours ago, PT20J said:

Nice job handling the emergency. 5500 feet isn't all that high -- probably less AGL -- and you made the Mayday call, found a landing spot and did all the troubleshooting you could.

The B nut on the fuel pump was probably loose at takeoff and vibration caused it to become a lot looser in flight. Since it was on the output of the fuel pump it could easily reduce fuel flow. The pump will attempt to maintain fuel pressure by increasing the flow, but most is going out the leak and not to the servo. The 3-6 gph you saw at cruise throttle probably drove the mixture too far LOP for combustion.

I had that same B nut come loose on my 1978 J. Fortunately, it was only slightly loose and I noticed it when returning to the plane after a short stop because gas was dripping on the nose tire. I was lucky because I had planned a long flight with my wife the next day over inhospitable terrain.  I tightened the fitting and never had another problem. I would expect that yours will be fine.

We're about to replace the fuel line on my F.  I was already concerned because the upper end behind the engine is so difficult to access.  Now I'm even more worried.  Hopefully the mechanic has some trick tools to allow him to get a good torque on the fitting.  I'm wondering now if it's better to leave well enough alone and not create a self inflicted problem.  The point of the exercise was to address the outstanding SB.  

[DXB]

On 4/19/2025 at 7:54 PM, Shiroyuki said:

Oil, fuel pressure were in the green.... I had plenty of fuel. Propeller was windmilling, there is no oil spraying everywhere or any catastrophic failure. The only thing abnormal, that I noticed, was when I turn on the boost pump there is a strong smell of fuel. During departure out of CYTZ, when I turn on the fuel point in the takeoff check, I also smelled a whif of gas but I did not thought to much about it.... They found the fuel line out of the engine driven pump to be loose at the connector, causing a very significant fuel leak. The reason why it is loose, according to the mechanics, is likely because the fuel line with fire sleeve over it was rubbing against the firewall, loosening it over time. Both mags are firing properly and sparks are produced on all 8 plugs.. I'm really not sure how do I trust this plane again. 

First and formost terrific job handling this!!  Combined with a little luck, your skills let you walk away from a dire situation, and the aircraft basically being fine is a nice bonus. As far as I can tell, the cause seemed likely to have been a transient obstruction like ice in a distal portion of the fuel system.  The leak discovered at the fuel hose attaching to the engine side of the firewall (proximal to any such obstruction) is serious but seems like a red herring here since you had good fuel pressure measured distal to it before and after the engine quit. I only wonder if you have a data logging engine monitor to help sort the events out a little better.  Your engine failure catches my attention because I've previously experienced two in flight anomalies, documented here on Mooneyspace in separate threads complete with engine monitor data (see below), that I ultimately attributed to small amounts of ice in the fuel system on cold winter days.  Of course my carb'd fuel system is quite different, and my engine didn't quit, but both events did scare me.   

A useful discussion point here might be: what is the best SOP to mitigate risk of ice crystals plugging fuel system components when operating in cold temps? Sumping may not catch such materials, which could have already been present in the fuel when it was pumped at very cold temps.    How cold should it be for one to think about it? What other factors contribute?  I know Avgas itself freezes at <-60-72F or so. I also know one can add up to 1% isopropyl alcohol to fuel.  When should one do this routinely? Does one need a full 1%?  Will that small amount of alcohol dissolve crystals that have already formed?  Does anything need to be done to mix the alcohol in? I find very little written out there on this topic.  

I think that answering these questions might give you the confidence to trust your bird again in the frigid northern latitudes - there's nothing intrinsically unreliable about it.