rangermb

Mystery Tube - Fuel Dripping When Flooded

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OK, I tried for an hour to get my plane started this afternoon.  IO-360-A32B6D 50 degrees (I know, Indiana in January?). Still preheated as it was cold last night.

I'm not looking for suggestions on how to start the engine, Might be my method, might be no spark. I'm going to try again tomorrow.

My question is - At one point I definitely flooded it and had fuel dripping pretty good out of one of three tubes that vent out at the left cowl flap. I know that one is the breather tube (not the one leaking). The one dripping fuel appears to run toward the front of the engine.

I'm not an expert at engine things (I fly 'em, I don't fix 'em). Any knowledgeable folks out there know what the other 2 tubes do (particularly the one dripping gas)?

Thanks to you motorheads out there.

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Where does excess fuel go?

 

one place it goes, Are you familiar with....

yes, it is called the sniffle valve... it’s a mysterious part... if it is leaking after a failed start, the ball/float/one way valve may need some cleaning... so get a pic of it... There is a piece, with a pin that keeps the ball in place... it’s whole purpose is to handle a small amount of fuel, but not turn into an air leak... (search on sniffle valve for more and proper detail)

the case vent has a drip of oil on in constantly...

Where is your battery? It will have a drain tube as well... your battery may be in the tail...

PP thoughts only, not a mechanic...

Best regards,

-a-

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Anthony is right. Sniffle valve.  If you flooded your engine, it is doing its job of draining excess fuel out of the manifold, just aft of your fuel servo...right above the muffler.  The third tube might be the fuel pump drip line.  If fuel is coming from that, your fuel pump needs work.  This is located on the aft side of the engine.  Sounds like you simply flooded it.  I know you are not looking for start advice, but I have found that my preheated engine can behave more like a warm start engine and tends to like similar start treatment.

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From an article on Don Maxwell's website:
"“J” models have the breather/vent, mechanical pump “weep” drain and induction drain all located in the left cowl flap area."

IIRC, the "weep" drain is from the mechanical fuel pump.  If the seals give, it drains the leaking fuel out the bottom instead of spraying into the engine bay, which is not good for obvious reasons

He mentioned IO-360's have a distinctive "loping" sound at idle because the sniffle valve leaks air in the induction manifold at low RPM's.

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If it’s the pump’s drain....

turn on the electric pump, and observe the drain... if anything comes out, the pump gets pulled for OH/reseal.... every 15-20 years or so...?

Best regards,

-a-

 

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Great, I think the sniffle valve is the culprit.

Thanks for the replies.

 

Mike

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The sniffle valves on these airplane are known to become clogged and may stick partially open causing induction leak causing irattic idle.  A quick bath in the ultrasonic cleaner is the cure.

Clarence

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The sniffle valves on these airplane are known to become clogged and may stick partially open causing induction leak causing irattic idle.  A quick bath in the ultrasonic cleaner is the cure.
Clarence


You got a picture of one of these?


Sent from my iPhone using Tapatalk Pro

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11 minutes ago, Marauder said:

 


You got a picture of one of these?


Sent from my iPhone using Tapatalk Pro

 

In the case of your Lycoming engine, it’s an AN elbow which has been modified with the addition of a small nylon ball and a cross pin to secure the ball in place.   It is in the bottom of the intake system, above the muffler.  

There is a short section of aluminum line on the elbow followed by a length of rubber tubing draining out the left cowl flap. With the engine off, gravity pulls the ball down allowing raw fuel from the induction system, with the engine running the ball is sucked up, closing the valve .

I cant find a suitable picture of the Lycoming version in a Mooney, but this would be the starting point.

FC8D5C06-D67D-46DF-852F-6A59AD72ABA2.jpeg

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3 minutes ago, carusoam said:

Great details again, Doc!

Thanks,

-a-

Here’s what the Continental version looks like, installed in the right exhaust fairing on the Ovation.

82BBF515-C06B-4B02-84E1-B5C4CEB4379E.png

310115F6-D261-4BC9-91F1-95C7EE1CF864.jpeg

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32 minutes ago, Marauder said:

 


You got a picture of one of these?


Sent from my iPhone using Tapatalk Pro

 

The only picture I could find.

A7C9E2BF-8D39-4780-A932-77300B1C4114.jpeg

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The Continental one Looks purpose built.  When you see it the first time, you want to know what it is...

The Lycoming one, you have to be searching for it already, then you will find it.  Otherwise it looks like an ordinary elbow, accept it has a pin through it.

Thanks to Doc, for supplying the tech details!

Best regards,

-a-

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Is every IO-360 supposed to have the sniffle valve?  Was just checking my Parts Bullentin for my 78 201, Ser 522...and sniffle valve is listed (Section 28-20-00, Item 63, 610122-501) however Has Note I...Note I details for serials 1-83, 85-377....

I'm curious how/why the need would be eliminated after that unless that also tied to some IO-360 variant where it was no longer required or factored into the fuel servo?  

Seems above discussion and other threads on the notorious sniffle valve indicate everyone should have one...but seeing otherwise in parts bulletin (in the middle of checking to see if I have one next cowl off!)

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Interesting question. Really, every horizontal induction IO-360 should have one to drain excess fuel from the induction system to prevent a potential fire hazard. Lycoming makes one (LW 75444) but the Lycoming IPC only shows it on the A1B6 and the A1D6. My factory rebuilt A3B6 didn’t come with one. The Lycoming part won’t work on a M20J, because of the close fit of the muffler which is why Mooney makes the right angle valve. 

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1 hour ago, Culver LFA said:

I just cleaned my sniffle in the ultrasound and installed it today! 

EAE9D365-E998-4723-88CF-B84CDAB3F0F8.jpeg

It's possible you might have an intake blockage.

 

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1 hour ago, Culver LFA said:

I just cleaned my sniffle in the ultrasound and installed it today! 

EAE9D365-E998-4723-88CF-B84CDAB3F0F8.jpeg

Is that the Ron engine?

Clarence

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29 minutes ago, EricJ said:

It's possible you might have an intake blockage.

 

Yes! And a massive fuel leak.

18 minutes ago, M20Doc said:

Is that the Ron engine?

Clarence

As a matter of fact it is, should be converting 100LL to noise real soon.

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