Fuel Leak

[JPA]

Hello, I have a 1978 j model, yesterday after a flight I noticed that there was a leak coming from the hose connected to the fuel pump like 3 drops per minute, eventually it stopped leaking ... I think it could be a seal in the fuel pump ... however I wanted to know if this happens to you every time you return from flying?

[67 m20F chump]

I think that is a sign the diaphragm in the pump is going bad.  I’m sure others will know for sure.

[EricJ]

+1 that's telling you that the diaphragm is failing and it needs attention, assuming you're talking about the hose that drains out the cowl flap?

In any case, fuel drips are not normal and should be addressed.

[Ragsf15e]

If it’s a few drops coming out the sniffle valve it’s fine.  Tube and origin are critical here.

[PT20J]

The sniffle drain hose comes out of sump. The purpose of the sniffle is to drain any fuel that accumulates in the bottom of the intake manifold (which is built into the sump) usually from over priming. The flow divider contains a valve to shut off fuel during shutdown. Nonetheless, a small amount of fuel remains in the injector lines and can drain out the sniffle after shutdown. 

The fuel pump drain hose comes out of the engine driven fuel pump. The fuel pump has two diaphragms for redundancy. The drain is between them. If that chamber has fuel in it it drains out the hose. When that happens, it means that the pump is leaking internally and needs to be replaced. BTW, there is a similar drain on the boost pump. It is located aft of the left cowl flap. 

Skip

[David Lloyd]

To add to Skip, the mechanical fuel pump has two diaphragms for redundancy.  The drain is between them.  If the drain can either have fuel or crankcase oil depending on if the upper or lower diaphragm is leaking.  Either can fail and will continue to pump fuel, for a while.

[Ragsf15e]

So there’s a sniffle drain, mechanical  fuel pump drain, breather tube, fuel sump drain and electric boost pump drain all under and around the nose.  Definitely important to be dead sure which is which to aid troubleshooting.

The actual exit points on the fuselage differ by model and year.  I highly recommend tracing the line back to the origin.

[JPA]

Thanks to all!


Sent from my iPhone using Tapatalk

[carusoam]

JPA,

Mooney Fuel leaks are not normal…

That many drops per time is a lot…

And may be a full stream when the pump is operating… and could get worse without telling you…

 

If you need help identifying what it is…. Pics and videos are a common practice around here…

Pump diaphragms fail with age and usage…   Getting them ‘re-sealed’ is not a lengthy process…

Pump drains are pretty easy to recognize… compared to the other tubes…

If it is the sniffle valve… they can be cleaned to behave better…

PP thoughts only, not a mechanic…

Best regards,

-a-