JPA Posted July 15, 2021 Report Share Posted July 15, 2021 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? Quote Link to comment Share on other sites More sharing options...
67 m20F chump Posted July 15, 2021 Report Share Posted July 15, 2021 I think that is a sign the diaphragm in the pump is going bad. I’m sure others will know for sure. 1 Quote Link to comment Share on other sites More sharing options...
EricJ Posted July 15, 2021 Report Share Posted July 15, 2021 +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. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted July 15, 2021 Report Share Posted July 15, 2021 If it’s a few drops coming out the sniffle valve it’s fine. Tube and origin are critical here. 1 Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 15, 2021 Report Share Posted July 15, 2021 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 3 Quote Link to comment Share on other sites More sharing options...
David Lloyd Posted July 15, 2021 Report Share Posted July 15, 2021 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. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted July 16, 2021 Report Share Posted July 16, 2021 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. 3 Quote Link to comment Share on other sites More sharing options...
JPA Posted July 16, 2021 Author Report Share Posted July 16, 2021 Thanks to all!Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 17, 2021 Report Share Posted July 17, 2021 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- Quote Link to comment Share on other sites More sharing options...
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