IO550N quits on roll-out

[VA FLYER]

This is a kinda generic question, but the IO550N in my M20L has developed an ugly habit of quitting on rollout after an otherwise perfectly normal flight. It's done this twice out of the last three flights and the MX guys can't find anything wrong. It just quits with no drama, as if you pulled the mixture to ICO. Fuel pressure shows normal level and the main pump is about two years old. Happened after a three hour flight, next flight was about 1 hour and it did not try to quit, next flight was about two hours and it tried to quit. Now that I've been through it, I can keep it from quitting altogether by bumping the boost pump. No, I was not out of gas: 25 to 30 gallons evenly distributed across both tanks. I've flown it about 200 hours and never had the problem before a couple weeks ago.

Suggestions?

[MatthiasArnold]

Vapor lock after longer flights?

[varlajo]

What is your mixture position on landing? Full rich (per POH) or last cruise setting (per Deakin @ Co.)?

[Fly Boomer]

1 hour ago, VA FLYER said:

Suggestions?

I have read about this happening to both 550s and 520s.  I would find a Continental expert and have them do a complete "fuel system setup".  It's a complicated process, and there is no shortcut.

[jlunseth]

Don't know if this is your issue but might give you a clue. I fly a 231. The turbos are generally set up very rich and on final approach I generally need to lean the engine out to keep it from burbling. It burbles because the engine is overly rich but making very little power. If I lean it out the burble goes away. When I get to the tarmac and start to roll out I have to remember to put the mixture back in. During the final descent the engine can be very lean but won't quite because the descent is helping the prop and driving the engine. When the engine is no longer getting that help on the tarmac it can stop unless I enrich it. Hence varlajo's question. If you are intentionally lean during the final approach the prop can stop during the rollout unless you enrich the mixture. That is what you are doing when you hit the boost pump. Instead, just push the red stick in.

Whether you are leaning during final or not, but boost pump gives you your clue. The engine stops because it is too lean. It was fine during the descent when the descent was helping the prop, but that stops when you are on the ground. Need more fuel.

[1980Mooney]

3 hours ago, VA FLYER said:

This is a kinda generic question, but the IO550N in my M20L has developed an ugly habit of quitting on rollout after an otherwise perfectly normal flight. It's done this twice out of the last three flights and the MX guys can't find anything wrong. It just quits with no drama, as if you pulled the mixture to ICO. Fuel pressure shows normal level and the main pump is about two years old. Happened after a three hour flight, next flight was about 1 hour and it did not try to quit, next flight was about two hours and it tried to quit. Now that I've been through it, I can keep it from quitting altogether by bumping the boost pump. No, I was not out of gas: 25 to 30 gallons evenly distributed across both tanks. I've flown it about 200 hours and never had the problem before a couple weeks ago.

Suggestions?

 

2 hours ago, varlajo said:

What is your mixture position on landing? Full rich (per POH) or last cruise setting (per Deakin @ Co.)?

Mike Busch says "don't go full rich" - leave the mixture where it is.

Landing

Every POH I've ever read instructs you to advance the mixture to full-rich on final prior to landing. Don't do it! Pouring cold fuel on a hot cylinder head simply can't be a good thing for cylinder longevity. I recommend leaving the mixture leaned out for landing and taxi. I also recommend setting the props to top-of-the-green RPM, not shoving them full forward the way the POH instructs. Of course, if you have to make a go-around or a missed approach, don't forget to advance the mixture and prop controls before throttling up to full power.

Operating Tips for Big-Bore Continentals - AVweb

2 hours ago, Fly Boomer said:

I have read about this happening to both 550s and 520s.  I would find a Continental expert and have them do a complete "fuel system setup".  It's a complicated process, and there is no shortcut.

 Until you do the full set-up of the Continental per SID97-3G (link below) you are just shooting in the dark.

Continuous Flow Fuel Injection Systems Adjustment Specifications and Instructions

The recommendation on Beechtalk for the same issue:

• "If you can't find a leak, have your mechanic perform the procedure called out in SID 97-3G, now included in the engine maintenance manual. Let him know that it needs to be performed as written, with no shortcuts allowed. When he or she thinks they nailed it, ask them to perform the run-up test procedure at least three times in a row to make sure it is repeatable. The three adjustments all interact in strange ways and the results are strongly dependent on whether you properly purge the fuel system prior to the next test. Also, make sure they properly apply the correction factor if the engine fails, as most do, to reach max rpms when the aircraft is not moving."

Here is what an owner with an IO-550N posted on Beechtalk in 2022 regarding exactly your same issue and solution with SID-97

• "I had exactly this behavior for over a year on my IO-550N. Lived with it with work-arounds such as keeping the fuel pump on, keeping revs above idle, etc. Eventually had it diagnosed as fuel pump setup being out of whack and has the SID 97 procedure done. It cured the problem completely and did not require purchase of any parts.

  The procedure took about 3 hours and I participated as the pilot operating the controls while the mechanic manipulated the fuel pump settings. It is a 2-person exercise, so I "saved" $300 by not having to have a second tech inside the airplane - plus it was a hell of an experience! The procedure is iterative by adjusting 3 things sequentially; each adjustment affecting the prior setting. IIRC, the parameters to be monitored were: idle rpm, idle fuel pressure, max rpm, max fuel pressure, and rise of idle rpm as mixture is leaned before cutout.

  It is potentially a very hazardous exercise as well as scary for a first-timer. The airplane has to be secured with tie-downs, full braking applied, and run up to full power for several seconds in each iteration. At 310 hp, the airplane was howling and bucking like a wild horse. We didn’t have tie downs on the ramp, so used double chocks and brakes - a really bad idea. During each iteration, at full power, I had to look down and record rpm and fuel pressure and on one occasion, the airplane jumped the double chocks and spun 90 degrees in the brief time I was looking down. When I looked up again, I was completely disoriented and hauled back the power before things became too exciting. I have seen pix of airplanes that rolled upside down when improperly secured during this operation.

  It is also a skilled job to know how to compensate for varying wind at each iteration. Each run up is done into the wind, and that could mean waiting for same wind speed each time and/or turning the airplane into wind that is varying direction.

  Bottom line, I learned a lot and problem solved."

 

[varlajo]

25 minutes ago, 1980Mooney said:

Mike Busch says "don't go full rich" - leave the mixture where it is.

Every POH I've ever read instructs you to advance the mixture to full-rich on final prior to landing. Don't do it! Pouring cold fuel on a hot cylinder head simply can't be a good thing for cylinder longevity.

 

This is one of the very rare instances where I consciously break St. Busch / St. Deakin's commandments. The safety consideration of not having to move three levers in the correct order in a potentially high-stress situation of a go around due to a bounce, "baby on the runway", or something else wins, in my humble personal opinion, over the cylinder longevity consideration. As a matter of fact, in the end of descent the cylinders are comparatively cool anyways. 

[1980Mooney]

1 hour ago, varlajo said:

This is one of the very rare instances where I consciously break St. Busch / St. Deakin's commandments. The safety consideration of not having to move three levers in the correct order in a potentially high-stress situation of a go around due to a bounce, "baby on the runway", or something else wins, in my humble personal opinion, over the cylinder longevity consideration. As a matter of fact, in the end of descent the cylinders are comparatively cool anyways. 

Huh...I guess I don't follow the logic.  In a go around, my hand (which had been on the throttle all the time during short Final) is spread out on the throttle, pitch/rpm and mixture knobs.  I press all three (3) knobs in simultaneously to "firewall forward".  I don't get the "move in correct order".  It is all 3 together - don't think and certainly don't put your head down to look - it's muscle memory reflex - it's by feel.   Easy peasy...Bullet proof....Fail-safe.  Given the angle of my hand, the mixture and pitch/rpm press in a little ahead of throttle.  

I do get your point if the pilot is fiddle/farting around with each push/pull knob individually (and worst of all looking down at the push/pull knobs).

In 25 years on a Continental IO-550A in a J, I have never pushed full rich on landing. And over a thousand touch and go's with no issues while pressing all 3 firewall forward in executing go-arounds.

Edited February 13 by 1980Mooney

[varlajo]

15 minutes ago, 1980Mooney said:

I press all three (3) knobs in simultaneously to "firewall forward".  I don't get the "move in correct order".  It is all 3 together - don't think and certainly don't put your head down to look - it's muscle memory reflex - it's by feel.   Easy peasy...Bullet proof....Fail-safe. 

I don't have the requisite spine and testicular fortitude for such transition from operating a single knob to reliably covering three, which may all be at somewhat different position each time. Given that the mixture knob is the farthest from the original hand position, I think it's the one that is the easiest to miss or to accidentally slip off of. 

(I do not possess enough knowledge to comment on simultaneous operation of engine controls in a IO-550A).

Edited February 13 by varlajo

[buddy]

Try leaving your mixture leaned out as you would when leaning during taxi. The one thing to watch out for when doing this is your RPM’s are going to be a little higher on landing.

[jlunseth]

Well, I don't know why we are having a discussion about landing with the mixture lean or rich. It may be a worthy topic, but we have not heard from VA Flyer what he is doing with the mixture, so it could just as well be an engine issue. All we can really say at this point, from the information provided so far, is that it appears to be an overly lean mixture. But why?

[RangerM20]

Unfortunately, this is an issue with a lot of Continental engines.  When I was in the Air Force, I was a recip engine mechanic on Cessna O-2's, which had a Continental IO-360, and these would occasionally quit on landing.  These engines have a two-circuit fuel pump, and were very finicky.  Both high rpm and idle fuel circuits were separate, and had to be constantly adjusted.  The plane had a spring-loaded position to the high pressure electric boost pump, and several pilots said if they gave that a shot, the engine would come back to life.  Cessna - and Continental, for that matter - always claimed that they never heard of any problems of this kind.

[N201MKTurbo]

I cruise LOP. When I descend I leave the mixture where it was. I know I can go to full throttle at that mixture setting without issue. Full throttle while LOP is plenty of power to go around.

This procedure doesn’t apply to all engines. Just to the 35 setups like mine out there.

[LANCECASPER]

17 hours ago, VA FLYER said:

This is a kinda generic question, but the IO550N in my M20L has developed an ugly habit of quitting on rollout after an otherwise perfectly normal flight. It's done this twice out of the last three flights and the MX guys can't find anything wrong. It just quits with no drama, as if you pulled the mixture to ICO. Fuel pressure shows normal level and the main pump is about two years old. Happened after a three hour flight, next flight was about 1 hour and it did not try to quit, next flight was about two hours and it tried to quit. Now that I've been through it, I can keep it from quitting altogether by bumping the boost pump. No, I was not out of gas: 25 to 30 gallons evenly distributed across both tanks. I've flown it about 200 hours and never had the problem before a couple weeks ago.

Suggestions?

I had the exact same thing happen twice on an Ovation I owned ten years ago. The fuel setup was checked by someone that knows the IO-550 intimately. We tested the Champion (massives) that we took out and all of them failed, with very high resistance. We ended up changing all of the spark plugs and it never did it again.

If your fuel set-up hasn't been done by someone that really knows these engines you might start there. Although it wouldn't hurt to check the resistance on your plugs. On troubleshooting  it's not always just one thing. Example, you might have been off for a long time on the fuel but your plugs were ok so it was working out. Now if the plugs are higher resistance it's to the point that you can't keep it running at low power settings. 

 

[ta2too]

On 2/12/2025 at 4:20 PM, VA FLYER said:

This is a kinda generic question, but the IO550N in my M20L has developed an ugly habit of quitting on rollout after an otherwise perfectly normal flight. It's done this twice out of the last three flights and the MX guys can't find anything wrong. It just quits with no drama, as if you pulled the mixture to ICO. Fuel pressure shows normal level and the main pump is about two years old. Happened after a three hour flight, next flight was about 1 hour and it did not try to quit, next flight was about two hours and it tried to quit. Now that I've been through it, I can keep it from quitting altogether by bumping the boost pump. No, I was not out of gas: 25 to 30 gallons evenly distributed across both tanks. I've flown it about 200 hours and never had the problem before a couple weeks ago.

Suggestions?

The same thing used happened to me. I found that if I ran the low boost fuel pump it would hold an idle. My mechanic set up the fuel system and that solved the problem.

[Pinecone]

21 hours ago, 1980Mooney said:

 

Mike Busch says "don't go full rich" - leave the mixture where it is.

Landing

Every POH I've ever read instructs you to advance the mixture to full-rich on final prior to landing. Don't do it! Pouring cold fuel on a hot cylinder head simply can't be a good thing for cylinder longevity. I recommend leaving the mixture leaned out for landing and taxi. I also recommend setting the props to top-of-the-green RPM, not shoving them full forward the way the POH instructs. Of course, if you have to make a go-around or a missed approach, don't forget to advance the mixture and prop controls before throttling up to full power.

The other thing is, how much fuel are you actually "dumping????????"

You are at a very low power setting with very low fuel flow.  Even doubling the fuel flow is not a lot of fuel.

[Brandt]

Have had the same issue.  As said low boost will keep it running.  Had the fuel setup checked by  Mooney and Maxwell.  Needed some adjustment but biggest issue was simply fuel loading during idle descent.  Leaning out a little on descent solved the issue. 

[Bolter]

I found internal fuel component leaks from dried out or ageing components, I think the engine driven fuel pump and flow divider.  The dying on roll out was rare, then became more common as the components got worse in ananalog kid of way.  Rebuilt all fuel system components and tuned per the manual, and the problem was positively gone.  Other than the stalling on roll out, there was no external indicator of the significant problem inside the fuel system.