Curious start up issue

[Browncbr1]

After pulling the top of the flow divider, we found the slightest amount of dark residue at the top of the bore from what looks like just normal wear from the piston moving up and down.  Diaphragm looked brand new after 6 years.  We found that the piston was kind of hanging up a little when reassembling.  It wouldn’t slide smoothly all the way in.   So we just used a qtip to try and pick up anything that might be in there.   Didnt see anything other than the slightest amount of that black residue.  The top of the piston had a little scoring on one side.   We just worked it in and out until it seemed to go in smoothly on its own weight.   Reassembled and ran it.   The issue was still there, but not as bad.   Did a normal run up and it went away and then idled smoothly at normal fuel flow.  Shut down and had the IA watch the fuel system as I shut down to see if any fuel exited the system.  Didnt see anything.    As I pulled the mixture, to shut down, I noticed There was almost nothing left to pull.  I gave three clicks lean on the idle mixture screw.  Started back up, huge backfire.  After that it settled in to a smooth idle with expected fuel flow.  I did rich to lean test and got close to 100rpm rise.   So I gave two more clicks lean following a normal shut down.  Normal start up, good smooth idle,..  so I flew it for about an hour and it ran very smoothly and on approach, landing, and taxi, it ran perfectly all the way to normal shut down.  OAT was 95F.   

I’ll check under the cowl for any fuel staining sometime next week.  None was found following the ground runs. 

Edited August 27, 2021 by Browncbr1

[carusoam]

Great details regarding fuel divider behavior Mr. Brown!

See if @M20Doc has a second to look over your shoulder… (fuel divider cleaning, everything seems right after that…)

Best regards,

-a-

[Guest]

I have had to carefully polish mark off the plunger before, it should be smooth and shiny with no signs of binding in the bore.  
 

Clarence

[Browncbr1]

On 9/2/2021 at 6:26 AM, M20Doc said:

I have had to carefully polish mark off the plunger before, it should be smooth and shiny with no signs of binding in the bore.  
 

Clarence

well, I polished the piston very well.  no marks or anything.. the piston slides up and down on it's own weight in the bore.  I ran the plane again and found that the symptom persists.  It is clearly getting too much fuel on the ground somehow.  It runs perfectly in the air and after flying runs fine on the ground...  I was ground running multiple times, as I was also balancing the prop... I found that following one shut down, when i got back in 5 minutes later to restart, the fuel pressure had reduced below the green.  Usually it should hold for that short amount of time.     I am wondering if there is a seal or something leaking internally in the servo that is creating a fuel metering issue that is sending too much pressure to the divider.  I don't see how it could be the spring in the divider.  I'm out of ideas at this point....  hoping someone could advise me that i should indeed go ahead an order up a rebuilt servo... 

Edited September 10, 2021 by Browncbr1

[EricJ]

Does it matter whether the boost pump is on or not?

 

[A64Pilot]

On 9/2/2021 at 6:26 AM, M20Doc said:

I have had to carefully polish mark off the plunger before, it should be smooth and shiny with no signs of binding in the bore.  
 

Clarence

felt wheel and jeweler’s rouge?

[Guest]

1 hour ago, Browncbr1 said:

well, I polished the piston very well.  no marks or anything.. the piston slides up and down on it's own weight in the bore.  I ran the plane again and found that the symptom persists.  It is clearly getting too much fuel on the ground somehow.  It runs perfectly in the air and after flying runs fine on the ground...  I was ground running multiple times, as I was also balancing the prop... I found that following one shut down, when i got back in 5 minutes later to restart, the fuel pressure had reduced below the green.  Usually it should hold for that short amount of time.     I am wondering if there is a seal or something leaking internally in the servo that is creating a fuel metering issue that is sending too much pressure to the divider.  I don't see how it could be the spring in the divider.  I'm out of ideas at this point....  hoping someone could advise me that i should indeed go ahead an order up a rebuilt servo... 

Check with Russ at D & G Supply in Michigan.

Clarence

[Browncbr1]

2 hours ago, EricJ said:

Does it matter whether the boost pump is on or not?

 

No, fuel pressure is in the green.  Too much fuel is going into the cylinders.   I talked with an engineer at avstar and he had a thorough understanding of the system, but was a little perplexed.  We settled to go back and check if any air is getting into the unmetered side of the servo regulator.   That would cause the regulator to open more fuel on the metered side.     So, I’m going to do the clear tube air bubble test starting at the nozzles and work my way back.  He said that sometimes, the larger fuel line fittings can leak air without leaking fuel.   The part that I don’t understand is that it’s fine in flight.  Ff and fp are stable.

[Guest]

4 hours ago, A64Pilot said:

felt wheel and jeweler’s rouge?

A soft cloth and polish and work it by hand.

[Browncbr1]

well.,,, i found all kinds of green goop around my sniffle valve on the bottom of the intake chamber.. i found it was leaking all over the muffler as well.  more than just a little.  and it is like a green heavy weight sticky oil that has wicked all over..   if it was straight fuel, it would evaporate, but maybe it is mixing with the oil from the fresh bracket air filter i just installed at annual...  Russ at D&G said he has seen a lot of green goopy oil getting into the intake from a bracket filter.

my next step is to remove it and bathe it in an ultrasonic cleaner....   my current thinking is that it is not actuating properly and allowing fuel to pool up in the intake, thus creating a rich condition until flying the plane..   however, I don't think this would answer why my fuel flow is twice what it should be during warm up idle..    at this point, i just want to eliminate this as a possible problem.  After speaking with Russ, he didn't seem to think the servo would dump fuel into the intake only after start and warm up, but then go away after a while..   

Edited September 13, 2021 by Browncbr1

[Shadrach]

24 minutes ago, Browncbr1 said:

well.,,, i found all kinds of green goop around my sniffle valve on the bottom of the intake chamber.. i found it was leaking all over the muffler as well.  more than just a little.  and it is like a green heavy weight sticky oil that has wicked all over..   if it was straight fuel, it would evaporate, but maybe it is mixing with the oil from the fresh bracket air filter i just installed at annual...  Russ at D&G said he has seen a lot of green goopy oil getting into the intake from a bracket filter.

my next step is to remove it and bathe it in an ultrasonic cleaner....   my current thinking is that it is not actuating properly and allowing fuel to pool up in the intake, thus creating a rich condition until flying the plane..   however, I don't think this would answer why my fuel flow is twice what it should be during warm up idle..    at this point, i just want to eliminate this as a possible problem.  After speaking with Russ, he didn't seem to think the servo would dump fuel into the intake only after start and warm up, but then go away after a while..   

Unfortunately this reads like the servo is destined for service.  If it runs fine after flight, the only real variable is heat.  If it were leaking, that would manifest itself hot or cold. 

[Browncbr1]

4 hours ago, Shadrach said:

Unfortunately this reads like the servo is destined for service.  If it runs fine after flight, the only real variable is heat.  If it were leaking, that would manifest itself hot or cold. 

Well, the other variable is volume and velocity of air that passes through the intake chamber.   I don’t think heat matters because I ground ran it multiple times and it was good and hot..   it seems like it really dumps a lot into the intake chamber after shutdown because hot starts are not the same as before..  but, you may be right in any case,.. I think if cleaning the sniffle doesn’t solve it, I’ll just bite the bullet and order a rebuilt servo.

Edited September 13, 2021 by Browncbr1

[Shadrach]

1 hour ago, Browncbr1 said:

Well, the other variable is volume and velocity of air that passes through the intake chamber.   

If it runs fine on the ground post flight, how is volume and velocity the other variable? Presumably those two things are nearly the same during ground runs whether pre or post flight.  Is flying the only way to clear the issue? Have you verified that a high power ground run up does not have the same effect?

[Browncbr1]

1 hour ago, Shadrach said:

If it runs fine on the ground post flight, how is volume and velocity the other variable? Presumably those two things are nearly the same during ground runs whether pre or post flight.  Is flying the only way to clear the issue? Have you verified that a high power ground run up does not have the same effect?

It seems that a standard 1700rpm runup clears it up, however, it also seems that the plugs have already become nasty by then, so flying cleans them up, then it purrs like normal after landing.  But even if it’s the intake plenum filling up after shutdown, that still would not explain the high fuel flow indication.   Just wanted to clean the sniffle and run it before spending money.  

Edited September 13, 2021 by Browncbr1

[Shadrach]

2 hours ago, Browncbr1 said:

It seems that a standard 1700rpm runup clears it up, however, it also seems that the plugs have already become nasty by then, so flying cleans them up, then it purrs like normal after landing.  But even if it’s the intake plenum filling up after shutdown, that still would not explain the high fuel flow indication.   Just wanted to clean the sniffle and run it before spending money.  

Makes sense to me. You have nearly double your normal fuel flow with a constant flow injection system and an updraft intake system. Every time the intake valve closes the fuel from that cylinder migrates down.

[carusoam]

Got pics of the green stuff?

If the sniffle valve is stuck open…. It will allow some extra air to enter the system…  leading to a more lean condition than normal… especially at low power on the ground… less noticeable at high power…

Clean and verify the ball is moving in the valve…

 

Sounds like two separate challenges…. High FF, probably isn’t related to the sniffle valve…

PP thoughts only, not a mechanic…

Best regards,

-a-

[Browncbr1]

I’ve got some good news to report.   
I took the sniffle off and bathed it in my ultrasonic cleaner.  I found a glob of what looks like some kind of sealant in the exit elbow tube.  I tested it with my mouth to make sure the ball is moving as it should.  I reassembled and started it up.  
 

wow, egts went straight up to 1300 and it was running like normal.  The fuel flow was initially higher, but it settled down after about 10-15 seconds like it should to about 2.0gph for warm up.  I had a 20min ground run due to traffic, but got airborne and it ran fine…. Came around after 10-15min and taxied in like normal.   I didn’t see anything come out of the sniffle, so I fished wire through the aluminum fitting that’s on the cowl and pulled the hose off..    the hose is dry.  I remember in the past, I might see some steam, vapor and maybe a drop forming at the end of the tube after flying.    My plan is to come back out later this week and fly again and see if things are normal again.   Perhaps remove the sniffle and inspect again before flying to ensure its opening to drain.  

[carusoam]

Great follow up with an Interesting pic Mr. Brown!

There is some info written about the Sniffle valve and some issues… around here somewhere…

The engine’s intake vacuum sucks up the ball and should keep it closed…

Gravity allows the ball to drop to let stuff out, after the engine is shut down…. Often excess fuel left from the start start process…

If you are really good with how much fuel you use to prime the engine… very little will ever show up coming out the drain…

If a bug managed to climb up the tube… his remains could have kept the ball from sealing…

PP thoughts only, not a mechanic…

Best regards,

-a-

[Browncbr1]

Back at the hangar today and found tons of green all over the sniffle valve again and the hose was completely dry.  It was clear to me that this valve is sticking closed.  I removed it and found that although I had verified that the ball is moving inside, it would not unseat from being closed without a little air pressure from blowing.  It would not fall open under gravity alone.  So I soaked it again in solvent, and this time I poured 100LL through it.  Nothing came out that I could see, but the ball would unseat a little better.   I flew 15min for a fuel run and no steam or anything was coming out of the tube after shut down..  so I restarted and flew for 30min to atleast clean up the plugs a little better.  After return shutdown, I now see steam/fuel vapor exiting the drain tube and no residue around the valve at the bottom of the case yet.   I have noticed in the past that the valve elbow feels like a pretty sloppy fit.  That’s how it’s always been as IIRC.  Maybe I need a new valve.   I also shortened the hose to make it turn sharper straight down to help shed any fluid quicker.  

is the fit of the sniffle elbow kind of sloppy in the fitting on everyone else’s ?

 

for the time being, I’m going to say the issue has been the sniffle valve all along.

Edited September 16, 2021 by Browncbr1

[carusoam]

The sniffle valve is a Mooney made part that uses an ordinary elbow fitting and machined to add the retaining pin…

So…. Expect it to fit like any other elbow fitting…

If it is a loose fit, and not air tight… that would be a cause for air to leak in… (?)

It may be possible somebody changed out the line somewhere in its history…

 

Newer Mooneys have a much more expensive sniffle valve that is purpose built and looks really fancy…. To do the same task…. 

Best regards,

-a-

[Ragsf15e]

On 9/16/2021 at 9:13 AM, Browncbr1 said:

Back at the hangar today and found tons of green all over the sniffle valve again and the hose was completely dry.  It was clear to me that this valve is sticking closed.  I removed it and found that although I had verified that the ball is moving inside, it would not unseat from being closed without a little air pressure from blowing.  It would not fall open under gravity alone.  So I soaked it again in solvent, and this time I poured 100LL through it.  Nothing came out that I could see, but the ball would unseat a little better.   I flew 15min for a fuel run and no steam or anything was coming out of the tube after shut down..  so I restarted and flew for 30min to atleast clean up the plugs a little better.  After return shutdown, I now see steam/fuel vapor exiting the drain tube and no residue around the valve at the bottom of the case yet.   I have noticed in the past that the valve elbow feels like a pretty sloppy fit.  That’s how it’s always been as IIRC.  Maybe I need a new valve.   I also shortened the hose to make it turn sharper straight down to help shed any fluid quicker.  

is the fit of the sniffle elbow kind of sloppy in the fitting on everyone else’s ?

 

for the time being, I’m going to say the issue has been the sniffle valve all along.

That’s awesome if it’s fixed, because that’s much cheaper than a fuel servo overhaul!