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Fuel leak after engine rebuild


willerjim273

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Anyone have any ideas? I am grounded until I get this figured out. 

1980 231. Less than 10 ours on new engine. The engine was done by Western Skyways. A local shop, Arapahoe Aero performed the swap. 

 

Flew the plane on Dec  28th-.  Put the plane away about 4:30 PM.  I pulled it out of the hangar yesterday, the 29th,  and let it sit on the ramp all day to help my son install a car stereo.

 

We pushed it back in about 7 PM and wow- as soon as I pushed it back, I saw something leaking from the bottom of the cowl. It was gas! looked in through the cowl flap opening and sure enough there was gas accumulated in the bottom flat  part of the cowl. 

 So the plane sat for over 24 hours and still had enough fuel in the bottom of cowl to leak out. Not good. 

 

Tks

 

Jim

 

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Likely a B nut on a fuel line wasn’t tightened properly during installation and backed off. It’s not a bad idea idea to change the oil at 10 hrs on a new engine and check security of everything. You won’t know for sure until someone removes the cowlings and looks. 

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I'm guessing it's the main fuel line that's wrapped up in the orange firesleeve with the fuel transducer if you're so equipped on the back of the firewall near the top.   If not, I'd check the fuel line going right into the spider assembly ontop your engine if that's where it is.  I'm not familiar with where everything is on the 231.  

One sure way to check is take the cowling off, run the engine at 1000 rpm's, and have a VERY qualified person like an A&P observe where the leak is coming from, otherwise it might be difficult to tell where it's coming from.

I had an issue on my previous 1998 J model, which the IA didn't even tighten the main fuel line right after overhaul,  it was not even finger tight.  He had already signed it off and told me it was ready to test fly.  If it wasn't for my insisting the cowling come back off and I check it over, I may have had a major accident on the test flight.  

Please keep us posted as to what the issue was.  

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Jim,

If you decide to do the decowling and poking around yourself...

Be cognizant of the hazards of fuel fires....

Low rh in the winter has a tendency to generate static electric sparks...

Have a fire extinguisher on hand...

 

Were you smelling any fuel aromas while flying?

Do you have a FF gauge?

Fuel leaks while parked, can turn into air leaks into the fuel system while flying....  air bubbles cause interesting FF anomalies.

PP thoughts only.

Best regards,

-a-

 

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Thank you all for the responses. 

 

Having just spent a TON of money and hearing from you all, I believe the best course of action is to let the shop that did the work take care or it.  If I  start messing with things then I open a can of worms, I believe. If it was not a fuel problem, I would just fly it down to the shop and drop it off. Now, it will just take time to have them get someone up here. 

I have no problem opening the cowling except as above. I USED to have a mechanic that would come to my hangar and oversee/sign off work we did on past planes:  EZE, M20E, turbo Vike, and others. I need to look harder for a replacement. Last mechanic's wife got real sick so he dropped out.  I am at 7CO0 near EIK and BJC. If anyone has any recommendations on a traveling mechanic in the Denver area, I am game. 

It has to be a big problem. Otherwise, how does fuel sit in the bottom of the cowling for over 24 hours and not all evaporate? Fuel leaks and turbos mix very well. It's just the big boom that bothers me. 

The good news is---no oil leaks!! 

 

Take care.......... everyone have a great New Year!

 

Jim

 

Oh- and to respond to your questions: No fuel smell while flying it 3 days ago, but there was an unusual miss on take off. After I hit the primer a few times and super tightened the mixture, it smoothed out.  I circled the airport for a few laps and went on with the flight.  She missed again doing pattern work  the same day. Both times on climb out. I landed at BJC and called the shop. The chief mechanic at AA said it could be dirt in a line or ..........etc,etc.  I got her home without any issues or misses.  I am sure he will take care of it. Just going to take more time to get them up here. 

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Rebuilt engines don't miss.   I think you have a loose hose fitting and you are sucking air.  You say no oil leaks, but If they missed one hose fitting, the oil lines may be next.  I would have to be there to watch over them, lest they find the one loose fitting and not check everything.  Including engine mounting bolts.

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On 12/31/2018 at 7:11 AM, Yetti said:

Rebuilt engines don't miss.   I think you have a loose hose fitting and you are sucking air.  You say no oil leaks, but If they missed one hose fitting, the oil lines may be next.  I would have to be there to watch over them, lest they find the one loose fitting and not check everything.  Including engine mounting bolts.

Since they messed up once have them use torque seal. https://www.aircraftspruce.com/catalog/cspages/crosschecktorqueseal.php

Have them put it on any nut or fitting that is secured and it helps not only the mechanics working on the engine but you to spot any fittings or nuts that are loosening in the engine compartment now for what ever reason and get ahead of any issues in the future, hope they find the and fix the problem soon.

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You could just go the the airplane, then with the throttle closed and mixture in cut off turn on the fuel boost pump and see if anything starts pouring out of the cowl.  It would at least confirm the suspicions.

Clarence

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^^^^ depending on what accessories were replaced and how the hoses were routed, it could be the mechanical fuel pump that failed and the fail hose is not routed properly. Might want to put a general location in your status.  There are people that will help if you are near by them.

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  • 3 weeks later...

Problem solved. Mechanic came up within 2 working days on the fuel leak. We were unable to duplicate the problem. Here is the best theory.

 

1.The crankcase fuel filter is routed down to the port firewall near the firewall and flap actuator. As it makes the curves, there is a horizontal section that should have more fall. 

 

2. Just outside of my hangar, the pad slopes maybe 5-7 deg. 

 

3.

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Problem solved. Mechanic came up within 2 working days on the fuel leak. We were unable to duplicate the problem. Here is the best theory.

 

1.The crankcase fuel filter is routed down to the port firewall near the firewall and flap actuator. As it makes the curves, there is a horizontal section that should have more fall. 

 

2. Just outside of my hangar, the pad slopes maybe 5-7 deg. 

 

3. Could be that the plane sat there for 24 hrs with fuel trapped in that section. Then when I pushed it back into the hangar, it drained out. That is the best we can do. Yes pulled the cowling and tried everything. 

 

Thanks guys. 

 

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