Stubborn MFI Fuel Tank Leak

[Wasatch 911S]

I have have made 2 attempts at stopping a fuel leak at the MFI supply fitting on the bottom of my gas tank on my '72 S. The first time I used the 22mm fiber washer that is on the parts diagram and that lasted about 2 days before it started seeping. The second try was with an aluminum washer and that lasted about month.

Does this have something to do with the ethanol in the gas or do these fittings with the filter go bad sometimes? If someone has a recommendation with regard to a different sealing ring material or some type of sealant to put onto the sealing ring that withstand the Ethanol fuel, please let me know. Thanks.

[Dmitry at Pelican Parts]

Hello - I'm attaching a link that I hope you find helpful from our site's DIY tech articles. If you have additional questions, please feel free to post a Comment just below the article and one of our techs will get back to you with details. Best of luck!

Porsche 911 Bosch Mechanical Fuel Injection Overview | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article

[cmcfaul]

How does the inside of the tank look or the screen filter inside the tank? If you take the fuel level sender off the top of the tank, it's easy to see what it looks like in there and if a reseal is needed.

Chris
73E

[matthewb0051]

^^^^^

I agree with Chris. Look in the tank and see if somewhere is leaking.

I don't think this is a leak from the outlet area. More likely a pinhole somewhere else that manifests near the area you are looking at.

You may want to replace the outlet or at least look at it to ensure that's not the problem.

[911pcars]

Short of a pinhole leak somewhere, try this:

Lacking new fuel inlet washes on a set of Webers, I coated the used fiber washers with a thin layer of Loctite 571 (sealant used for engine cases). Allowed to dry overnight. Nice tight seal.

Drain fuel from tank and remove the hose fitting so this area can be cleaned and dried. Confirm sealing surfaces are flat and/or not distorted. Apply sealant to both sides of the new seal or all sealing surfaces, then reinstall. Allow to dry/cure overnight, then test with a half gallon of fuel.

If that doesn't work, proceed to other, more involved repair solutions.

Sherwood

[Wasatch 911S]

Thanks everyone for all the great suggestions. I ended up using a copper washer and some of the sealant (571) that 911pcars suggested. That solved the drip which was good news because was you mentioned the next suspect was the tank itself.