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Questions about engine stoppage

N941WR

N941WR

Legacy Member
With over 60 flown in my -9 in the past month and a half I have experienced one in flight engine stoppage and two while rolling out after landing.

All three events happened after prolonged flights at low power or idle with the boost pump and carb heat on while burning 100LL. Such as following three J-3's into an airport for a fly-in. Never did the engine even sputter during normal operations.

My setup is per the plans, other than the installation of the fuel flow meter with the boost pump is on the cabin side of the firewall.

After much thought and investigation, I believe the cause was possible vapor lock in the un-insinuated 180 degree loop I put in the fuel line between the gascolator and the fuel flow meter. Click on this picture:



The fuel line was insulated three days ago but have not test flown the airplane yet. Once I test fly it, I will post my results here and on my web site.

The purpose of this post is to get the message out and to see if anyone else has had a problem with a similar installation.

I suspect this might be unique to my small engine sipping fuel at idle but I can’t say for sure.

(I know there are other places to put this meter but that is not the purpose of this thread, so please do not contribute to thread drift as this is an important safety issue. - Thanks.)

Search words: fuel flow meter line gascolator location service bulletin
 
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I would strongly consider changing that aluminum fuel line out for an appropriate fire sleeved hose.
 
Bill,
Vapor lock is a possible, but I'm curious; were you operating your electric boost pump at the time of these stoppages? I assume it is located inline on the cabin side of the firewall?
 
Also, if your airplane is carbureted, be sure that you do not have a sinking float... it can cause over rich mixtures at low power settings and can cause engine stoppages.
 
JonJay said:
I would strongly consider changing that aluminum fuel line out for an appropriate fire sleeved hose.
Click to expand...
Jon,

That was done on Sunday. Fire sleeve was slipped over the aluminum line. More testing to follow. I'm not a big fan of flexible fuel lines, except where needed.

DanH said:
Bill,
Vapor lock is a possible, but I'm curious; were you operating your electric boost pump at the time of these stoppages? I assume it is located inline on the cabin side of the firewall?
Click to expand...
Dan,

Yes, the boost pump was on each time and my setup is per the plans, other than the fuel flow.
 
Chickenlips said:
Also, if your airplane is carbureted, be sure that you do not have a sinking float... it can cause over rich mixtures at low power settings and can cause engine stoppages.
Click to expand...
If that was the case, it would happen all the time and power wouldn't come back up when I give it fuel. (One of the times it died I was able to catch it with more throttle.)

Besides, the carb was yellow tagged prior to instaltion and the OH included a new float.

I'm not thinking that it is a carb issue.
 
Bill,

Coupla thoughts:

180 deg aluminun loop I think your aluminum loop is fine - those are all solid mounted items (gascolator to fuel flow sender) on your firewall, but yes, most definitely firesleeve it as it will get hot particularly when power settings are low. If you replace with regular flex hose with firesleeve that might further help reduce the heat, but its probably not worth it.

Low power or idle? How low of a power setting is that exactly? To follow a Cub, I bet you are barely above an idle.

Idle can definitely be an issue. At idle, particularly if winds are funky and gusty, an errant wind gust can load up the prop and slow the engine down enough to stop the engine. Ask me how I know? I set my idle a little on the low side; I landed on a gusty day and my prop stopped on roll out. It certainly got my attention!:eek:

All I had to do was bump up the idle. It was around 500 and I bumped it to 600.
 
N908RV said:
Bill,

Coupla thoughts:

180 deg aluminun loop I think your aluminum loop is fine - those are all solid mounted items (gascolator to fuel flow sender) on your firewall, but yes, most definitely firesleeve it as it will get hot particularly when power settings are low. If you replace with regular flex hose with firesleeve that might further help reduce the heat, but its probably not worth it.
Click to expand...
I agree 100% and firesleeved the existing loop. I have no desire to replace it with a flex hose.

N908RV said:
Low power or idle? How low of a power setting is that exactly? To follow a Cub, I bet you are barely above an idle.

Idle can definitely be an issue. At idle, particularly if winds are funky and gusty, an errant wind gust can load up the prop and slow the engine down enough to stop the engine. Ask me how I know? I set my idle a little on the low side; I landed on a gusty day and my prop stopped on roll out. It certainly got my attention!:eek:

All I had to do was bump up the idle. It was around 500 and I bumped it to 600.
Click to expand...
This has been brought up and my idle is around 650 RPM so I doubt that is it but it is possible. The first time it happened in flight, I was doing about 65 MPH, maybe less and it was gusty. The other two times, I was rolling out, probably doing 30 MPH +/-. If the insulation on the line doesn't solve it, I will pump the idle.
 
Here are some other things to check:

Blast tube to gascolator
Blast tube to flow meter
Blast tube to mechanical fuel pump

These are all easy to install and can do no harm.

Also check idle mixture.

Vern
 
With over 60 flown in my -9 in the past month and a half I have experienced one in flight engine stoppage and two while rolling out after landing.
Click to expand...

Bill, after you have had a chance to change clothes ;) check to make sure the idle mixture on the carb is set properly. Sounds like it may be going either too lean or too rich.
 
vlittle said:
Here are some other things to check:

Blast tube to gascolator
Blast tube to flow meter
Blast tube to mechanical fuel pump

These are all easy to install and can do no harm.

Also check idle mixture.

Vern
Click to expand...
Vern,

Already considered installing blast tubes and boxing in the gascolator & flow meter but will wait until after my next test flight.

Sam Buchanan said:
Bill, after you have had a chance to change clothes ;) check to make sure the idle mixture on the carb is set properly. Sounds like it may be going either too lean or too rich.
Click to expand...
Sam,

No changing of clothes needed. It didn't even raise my blood pressure. I do remember the first time it happened, I was at 400 feet and short final and thinking, "Now isn't that interesting? I know what too do! Best glide. Check fuel. Full tank. Mag switches on. Hit starter. Hey, it's running again! Ok, land." It takes longer to read that than perform it.

I suspect the carb is OK. The reason being is this only happens after prolonged flight at idle/low power and not when performing a normal pattern. This why I'm almost certain it is heat related. However, you could be correct. Again, something I will look into after the next test flight.

Besides, too rich and I would see black exhaust; which is not the case. I've some better pilots than me fly formation and they never reported anything like that. Lean is a different story but my CHT's and EGT's are all in line under idle.

Any other suggestions? Keep 'em coming!
 
No changing of clothes needed. It didn't even raise my blood pressure. I do remember the first time it happened, I was at 400 feet and short final and thinking, "Now isn't that interesting? I know what too do! Best glide. Check fuel. Full tank. Mag switches on. Hit starter. Hey, it's running again! Ok, land." It takes longer to read that than perform it.
Click to expand...

Good on you, Bill! That is the way it's supposed to be.

I suspect the carb is OK. The reason being is this only happens after prolonged flight at idle/low power and not when performing a normal pattern. This why I'm almost certain it is heat related. However, you could be correct. Again, something I will look into after the next test flight.

Besides, too rich and I would see black exhaust; which is not the case. I've some better pilots than me fly formation and they never reported anything like that. Lean is a different story but my CHT's and EGT's are all in line under idle.
Click to expand...

An incorrectly set idle mixture screw won't manifest itself in cruise. At rpm higher than idle the idle circuit isn't in play so your buddies can't determine whether or not it is set properly. :) Prolonged idle is precisely when I would expect the engine to either load up due to a slightly rich setting or starve due to a lean setting. CHT and EGT won't tell you anything at idle about how the idle mixture is set.
 
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650 rpm

N941WR said:
This has been brought up and my idle is around 650 RPM so I doubt that is it but it is possible. The first time it happened in flight, I was doing about 65 MPH, maybe less and it was gusty. The other two times, I was rolling out, probably doing 30 MPH +/-. If the insulation on the line doesn't solve it, I will pump the idle.
Click to expand...

Bill, I agree, that is a healthy idle, I don't think you should have to bump it up - certainly no more than 700. I think you are right, heat is probably the culprit due to slow flight for extended periods.
 
Funny, the O-290 in my Grumman used to do this exact same thing. After the idle mixture was adjusted it ran fine. Just another data point.

mcb
 
Sam Buchanan said:
An incorrectly set idle mixture screw won't manifest itself in cruise. At rpm higher than idle the idle circuit isn't in play so your buddies can't determine whether or not it is set properly. Prolonged idle is precisely when I would expect the engine to either load up due to a slightly rich setting or starve due to a lean setting. CHT and EGT won't tell you anything at idle about how the idle mixture is set.
Click to expand...
Sounds like I will have to keep this in mind if the fire sleeve doesn't solve the problem.

mburch said:
Funny, the O-290 in my Grumman used to do this exact same thing. After the idle mixture was adjusted it ran fine. Just another data point.

mcb
Click to expand...
Matt,

Could you give me some details? Did this happen after prolonged idles or just anytime you throttled back to land? I've pulled the throttle all the way back at cross wind at a large airport and didn't have the problem. That's why I ask.



Keep it coming gang, this is very helpful!
 
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Bill
I have a similar set up as yours but a carbed 320. I covered that pipe with fire sleeve from the very beginning and have never had a problem. That may not be your problem, but at least it's another data point.

Cam
 
N941WR said:
Could you give me some details? Did this happen after prolonged idles or just anytime you throttled back to land? I've pulled the throttle all the way back at cross wind at a large airport and didn't have the problem. That's why I ask.
Click to expand...

For me it always happened on landing rollout. I'd be rolling down the runway and the prop would stop turning. I sold the airplane (with full disclosure!) and the new owner later told me that a simple adjustment to the idle mixture cured the problem. Sorry I don't have any other details.

mcb
 
50 rpm increase at ICO

Bill,

Sam and Matt have good points on the Idle Mixture. This is really easy to check and it could be a possible cause. With the engine warmed up, set the throttle at idle - 650 rpm and pull slowly and evenly back to Idle Cut Off.

Did you get a 25 to 50 rpm rise?

If you have less than 25 you are too lean, if more then 50 too rich. Here's the procedure for adjustment:

http://www.sacskyranch.com/eng135.htm

If your adjustment is off it is easy to fix.

Rob
 
fuel line

Hey Bill...Just a thought. Avgas or Mogas?? Mogas with ethanol could exasperate this vapor issue, but you would most likely see issues at altitude, also...adequate carb heat?? You could be icing at those low power settings. I have an identical setup in my 9A, and appreciate the input from your post. I will firesleeve my U bend...

HTH...Chris
 
carguy614 said:
Hey Bill...Just a thought. Avgas or Mogas?? Mogas with ethanol could exasperate this vapor issue, but you would most likely see issues at altitude, also...adequate carb heat?? You could be icing at those low power settings. I have an identical setup in my 9A, and appreciate the input from your post. I will firesleeve my U bend...

HTH...Chris
Click to expand...
Chris,

I'll update my first post. I was running 100LL and had carb heat on. At first I thought it might have been ice but that was not the case.
 
Bob Collins said:
The title of this thread refers to a "fuel line service bulletin."

Is there one?
Click to expand...
Bob,

I titled this thread that way to get people to read it.

The 180 degree bend for the fuel flow meter was copied of off of someone else's web site. A number of others builders have installed their fuel flow meter in the same manor and it would stink if they skipped this post because of the title and bent some aluminum, thus the original name.
 
Bill,
When I was a student pilot and we did sim engine outs, my CFI would periodically throttle up for a few seconds when we were in an idle glide to the landing spot. He said it was due to the engine loading up during prolonged idle. I do the same thing now in a long idle situation.
Probably not your problem but something to try.
 
N941WR said:
Bob,

I titled this thread that way to get people to read it.

The 180 degree bend for the fuel flow meter was copied of off of someone else's web site. A number of others builders have installed their fuel flow meter in the same manor and it would stink if they skipped this post because of the title and bent some aluminum, thus the original name.
Click to expand...

The reason I changed the title is because of possible confusion over the term "service bulletin". Service bulletins are generally issued by the manufacturer (Vans) and in my opinion should not be confused with a possible issue (still unverified at this point) raised by a builder.

Bill, your concern is valid, thanks for bringing it to our attention, but I believe it would be appropriate to not use "Service Bulletin" in the title of the thread.
 
Aluminum Fuel Lines Fire Wall Forward

I thought that was a no no? Not sure why I thought that, but seems like many people are doing it. Just curious what the Tech Advisors have to say about it. (not trying to hijack the thread)
 
Interesting

I have a O-360-A1A and I modified the carburetor to the rich version per the Precision Airmotive mod instructions with their mod kit. In the process I adjusted the needle valve in the carb to the specified dimension. There are times during landing roll out (and when I close the throttle on approach with an imperfect mixture setting) that I know the engine is about to shut down but I can feel it, hear it and see it. I just open the throttle slightly and the anemic situation goes away. I don't think you fully supported between closely spaced rigid mounted units with no relative motion aluminum (looks like 3/8") fuel line is any problem. I think the answer is operational - if it wants to quit when you are starving it - don't do that. I landed at Winston-Salem a year ago on an instrument approach ahead of a Falcon jet doing about 160kts just off the end of the runway. I pulled everything back and flew sideways down the runway to get as much aerodynamic drag as possible when it slowed enough to set it on the runway I was busy doing everything necessary to get it stopped and evaluate when to commit to the turn off the end of the runway - the engine and prop stopped. I don't think there is any need for a physical change in you set-up.

Bob Axsom
 
Had Your Tach Checked?

Have you strobed your prop to check that the tach is accurate? 650 rpm that's really 575 can really tilt your brain.
 
Bill,

I wouldn't rule out carb ice (unless you have a carb temp guage). Those little carb heat muffs that Van supplies give very little heat. Under the right conditions, an underperforming carb heater can contribute to carb ice. That's why they say to never use partial carb heat.
 
One our of testing and...

No engine stoppage.

I climbed to 7000 AGL, turned on the fuel pump, pulled the carb heat, throttled back, put out all the flaps, and slowed to 65 mph. After what seemed like forever and 3,000 feet, I slowed to 60 mph for another 1,500 feet. Nothing, not even a bump.

Idle was around 880 RPM at these speeds and 760 RPM just before shut down.

I'll do some more testing in the coming weeks but it looks like fire sleeve may have solved my problem.

To answer some of the other questions on this thread:

1. Yes, I had my tach checked before the first flight. With the Dynon EMS running off the P-mags, it is spot on.
2. I don't see a problem running an aluminum fuel line FWF as the gascolator is also aluminum. One will melt just as fast as the other. Also, the line in my installation is well supported and fire sleeved (now). Four Tech Advisors have inspected it and no one raised it as an issue.
 
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Just for a data point, I idle on the ground at 380-400 (yes, calibrated) for the braking effect on final. Rarely if ever pull all the way back on the ground except on rollout. I have never had a miss. IMHO, you should be able to idle at least at 500 without problems. I am running a three blade Catto, so I don't have a big flywheel out there, either. I would look very closely at idle mixture.

Bob Kelly
 
N941WR said:
Besides, the carb was yellow tagged prior to instaltion and the OH included a new float.

I'm not thinking that it is a carb issue.
Click to expand...

I recently replaced the float in a new Precision carb after the carb was in service only 20 hours. One half of the float was flooded, the other was not.
The engine ran ok at high power settings but would run bad at idle.
 
rvbuilder2002 said:
I recently replaced the float in a new Precision carb after the carb was in service only 20 hours. One half of the float was flooded, the other was not.
The engine ran ok at high power settings but would run bad at idle.
Click to expand...
Scott,

Thanks for the note, my engine runs good at idle (always has) and at high RPM's. That's why I discounted the float issue.
 
N941WR said:
2. I don't see a problem running an aluminum fuel line FWF as the gascolator is also aluminum. One will melt just as fast as the other. Also, the is line in my installation is well supported and fire sleeved (now). Four Tech Advisors have inspected it and no one raised it as an issue.
Click to expand...

I don't think melting of the fuel line is the main concern. Aluminum lines can break overtime from the frequent vibrations of the engine. This was the same problem (they would break in outlets that were used a lot) with houses wired with aluminum. The fuel line develops a slight crack and sprays the FWF with fuel. FIRE! I believe there is a thread somewhere on VAF about it. I believe it happened to one member on the ground or in flight. I changed mine with the advice on the thread combined with our DAR's advice.
 
TSwezey said:
Aluminum lines can break overtime from the frequent vibrations of the engine. This was the same problem (they would break in outlets that were used a lot) with houses wired with aluminum. QUOTE]

Actually, the house wire problem stemmed from different metal thermal expansion rates. The AL expands more than the copper screws in the outlets and worked them loose, causing arcs.
Click to expand...
 
WSBuilder said:
Actually, the house wire problem stemmed from different metal thermal expansion rates. The AL expands more than the copper screws in the outlets and worked them loose, causing arcs.
Click to expand...

See you learn something different everyday. I always thought you would have to use an outlet many times to crack the wire. But do you agree with the AL fuel line?
 
TSwezey said:
See you learn something different everyday. I always thought you would have to use an outlet many times to crack the wire. But do you agree with the AL fuel line?
Click to expand...
The problem with the wiring was the different expansion rates of the two dissimilar metals. This became a problem when the fixtures were heated when electricity passed through them, causing the wires to come loose, thus creating a fire hazard. That's why we no longer use aluminum wire in houses (and mobile homes).

Since we aren't putting electricity through these items, I don't see it as a problem. If it was a problem, we wouldn't use aluminum fittings at the fuel pumps and any other place where we connect aluminum to steal.

That?s my story and I?m sticking to it.
 
See you learn something different everyday. I always thought you would have to use an outlet many times to crack the wire. But do you agree with the AL fuel line?
Click to expand...

No.

Aluminum tubing is commonly used on RVs for fuel lines (it is shipped as part of the kit!) and has many reliable hours of field history. It is important to properly install, shield, and support fuel lines and fittings regardless of material, but there is nothing intrinsically wrong with aluminum.
 
Cracking Fuel Lines

Sure, the tubing can crack. If the tubing is made such that it can't "spring" between the attachments it gets stressed. If the attachment devices are of different mass they will resonate (vibrate) at different frequencies and stress the tubing. Whenever you can make generous bend radii and allow length to ensure the tubing isn't a structural load-bearing connection that's good. You can also work-harden the tubing when bending it and that promotes cracking. Some folks post-bend "cook" tubing to stress relieve. 300F for 5 or 10 minutes and slow cool. Fire sleeve it to prevent spraying the engine and make it easy to inspect, too.
 
OT: Another Wiring Explanation....

Being a firefighter in a town where most of the houses were built in the age of aluminum wiring (the 70's), the explanation I have always been told (and have observed) has not been differential expansion, but different metal corrosion. The original sockets were all aluminum - they wear out, people put in copper. You get dissimilar metal corrosion, and that raises the resistance, heats it up, and bingo - Outlet fires!!
 
Well I decided to go to my Home Inspection books for the home Aluminum problem and here is what is listed:

The Idiosyncracies of the Problem: The problem is not with the wire itself, it is intermittent hot connections where the wires join together or connect to devices. The reasons for this are not absolutely known but seem to center on the following factors:

1. Aluminum wire has a higher coefficient of expansion than copper and expands more when current passes through it. This can contribute to loosening at the connections.
2. Aluminum wire must be slightly thicker than copper to carry the same loads and this sizing difference may have contributed to loosening connections in early applications.
3. Metals in an oxygen atmosphere oxidize. Copper that oxidizes forms a conductor while aluminum oxide is a resistor. The resistance at the connections causes heat to build.
4. Unlike metals which connect can cause an oxide build as well and this may have caused an increased difficulty when aluminum wire was joined to devices intended for copper wire. The oxide added resistance.
5. The problem seems to increase as time goes by. This would seem to be due to increased loosening and oxide build.
 
Aluminum House Wiring

I guess we should start a new group dedicated to the ill effects of aluminum wiring in mobile homes. :D

Extremely entertaining.......
 
Former Mobile Home Dweller

When I was young and poor I inspected the duplexes (outlets) in my post-honeymoon mobile home. Reports of fires were rampant. True enough, I found all the wires corroded and all the (copper) outlet screws loose. The trouble isn't necessarily with having AL wire, but in having different materials in the outlets and service boxes. If they were all the same it wouldn't be an issue. With copper prices the way they are you would think the switch to all AL would be looked at, again.
The RV relevance is the lesson learned on dissimilar metals (just to get back on track).
 
Carb temps

During yesterday's flight I kept a close eye on my carb temps and a funny thing happened.

The carb temp actually went up when I pulled the power back and slowed down w/o applying carb heat. They were as high as 103, well out of the carb ice range.

Applying carb heat did raise the temps a little more but well out of the range where carb ice would have caused my engine stoppage, as I thought.

It looks like putting the fire sleave on the fuel line may have just solved the problem.

One additional word of caution for those of you doing the same setup, I did hear from one builder who had seen the flow meter crack where the fuel line exits the meter and heads to the engine driven fuel pump. He suggests that you add an Adel clamp to support the fuel line as it crosses the engine mount but still leave enough flex for the engine to move.

He went on to say that there are possibly two reasons why the flow meter cracked. 1. The fuel line might have been a bit tight and 2. the fitting in the flow meter may have been over torqued.
 
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Ironflight said:
Being a firefighter in a town where most of the houses were built in the age of aluminum wiring (the 70's), the explanation I have always been told (and have observed) has not been differential expansion, but different metal corrosion. The original sockets were all aluminum - they wear out, people put in copper. You get dissimilar metal corrosion, and that raises the resistance, heats it up, and bingo - Outlet fires!!
Click to expand...

I think this is closer to reality. The answer to the problem was copper clad aluminum wire, which I believe is still allowed in most building codes. However, most people are still scared of aluminum and won't use it. We may see it come back if copper keeps going up and up in price.

Larry
 
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