Questions about engine stoppage

[N941WR]

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

[JonJay]

I would strongly consider changing that aluminum fuel line out for an appropriate fire sleeved hose.

[DanH]

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?

[Chickenlips]

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.

[N941WR]

Originally Posted by JonJay

I would strongly consider changing that aluminum fuel line out for an appropriate fire sleeved hose.

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.

Originally Posted by DanH

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?

Dan,

Yes, the boost pump was on each time and my setup is per the plans, other than the fuel flow.

[N941WR]

Originally Posted by Chickenlips

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.

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.

[N908RV]

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!

All I had to do was bump up the idle. It was around 500 and I bumped it to 600.

[N941WR]

Originally Posted by N908RV

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.

I agree 100% and firesleeved the existing loop. I have no desire to replace it with a flex hose.

Originally Posted by N908RV

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!

All I had to do was bump up the idle. It was around 500 and I bumped it to 600.

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.

[vlittle]

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

[Sam Buchanan]

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.

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.