Fuel Tank Flange Leaking

[leif]

Hey guys,
Wondering if anyone can point us in the right direction. Our fuel tank leaks out of the top flange where the wires for the fuel pump exit the tank. We have tried rubber washers to seal the leak but they have still leaked when fuel sloshes and reaches the top of the tank. The copper washers around the bolts that hold the top flange in place seem to work well and not leak, should we just use more copper washers at the wire holes or look for a different material (some sort of plastic, etc)?
Thanks

[Kirk Feldkamp]

Can you share some photos or screen grabs of the tank in question?

-Kirk

[Owen Thomas]

Are the wires just running through a hole in the tank, or is there some kind of fitting there? It's hard to picture since you mention a flange, a hole, and the ability to use washers.

I think the proper way to do something like that would be to run a bulkhead connector and seal it up with copper crush washers, although a rubber seal should do the trick too. Alternatively, if it is just a hole, the quick n' dirty fix would be to gob some silicon in there.

[Drew Price]

Ditto on silicone.

I have found that Permatex brand 'Ultra Black' oil resistant RTV works well around fuel systems - it won't dissolve like some other sealants and adhesives around fuel. I used that to patch a leaky EVAP tank pressure sensor in my daily driver 2 years ago, still stuck strong on there. I imagine you guys have that up there in Canada.

I know from experience that JB Weld is porous to gasoline, especially while it's curing.

You can also buy Viton in sheets to make a proper gasket, but that will be more expensive.

[leif]

Thanks for the quick replies guys. Sorry about leaving the pics out, i guess that would make a lot more sense.



The problems in question are coming from the power and ground to the pump. The flange bolts were leaking, and those have been fixed with the rubber/copper washer combo. Since the clearance is so tight between the two wire holes I'm not sure what the best option is. Ideally the solution won't be permanent, and will allow for disassembly.

[Owen Thomas]

Definitely copper crush washers. If they don't fit because of clearance, grind them into a "D" shape but leave as much material as possible. It'll be a bit of a pain in the arse to tighten the nuts down, but it shouldn't be that bad. You could probably use plastic washers instead, that might be easier to tighten and should seal just fine.

[Kirk Feldkamp]

I've used this product before on a damaged fuel tank on a LeMons car. It worked great! I think we got it at ACE Hardware, but you can probably find it most anywhere. In this case, it might make sense to "pot" the wires using this stuff into the insides of the pass through fittings you have rather than trying to depend on what looks like some sort of less-than-adequate shrinking o-ring seal. Finally, make sure your vent is working properly too. A little pressure goes a long way with a relatively thin fluid like gasoline!

On a side note, it looks like you're potentially installing the pass through fittings incorrectly. I think the circular base next to the threads is supposed to provide the stop on the outside, while you actually nut (or double nut) from the inside. Also, stat-o seals (aka the washers with the o-rings on the inner diameter) generally only get installed on the inside of the tank. Finally, the clearance holes, copper washer, and o-ring for that size faster look rather large at first glance. If possible, try to spread the load more evenly from the head into the flange by using flange head bolts and washers that fit properly. If the fasteners are working properly, you usually don't need special sealing washers and all that to seal the tank flange. Also, look around for "sealing washers" if you really feel the need to use something there. I know McMaster sells them, but a lot of hardware stores around here do too. They're basically a metal washer that has one side overmolded with rubber. They can provide a much cleaner installation. Copper washers are just "expensive washers" if you put something underneath them like an o-ring. Normally they ARE the sealing ring (via deformation).

-Kirk

[rjwoods77]

The old FSAE Walbro fuel pump kits came with a single sealing washer (triangle rubber shaped on the inside) that worked great. They offer a version through McMaster that may work the same...

http://www.mcmaster.com/#stand...ling-washers/=m6f7qq

...you would be wise to check the material compatibility with all of your fuel tank pass through fitting including that white spacer.

[leif]

Thanks a lot for the information and the really good advice. We ended up using a sealing glue like the seal-all linked. That worked for the two wire terminals and the return line.
We'll double-check the passthrough fittings and the stat-o-seals. Right now there are no leaks and the car is purring, we're hoping to finally start testing this week.

[Sormaz]

why do the holes need to be so close together?
make a new plate with them further apart