fuel pump leaking same place on two cars

[Seth Rose]

I have a 69 Sedan Deville and a 72 Fleetwood 472 engine in my 67 Hearse. Both are leaking at the fitting on the fuel pump. the threads seem good, and I've got them pretty snug. Any ideas would be great. Thanks.

[cadillactim]

Try using Teflon tape on the male threads. Also make sure the line is going in straight into the fuel pump fitting.

Tim

[joeceretti]

Here is a very informative article on what to use to seal fuel lines and why...

http://www.jamestowndistributors.com/userportal/document.do?docId=563

I use what the airplane guys use. Leaky fuel lines for them are much worse than they are for us.

[Glen]

Teflon tape should not be used on flare fitting which is what is normally used on fuel lines.  The threads on a flare fittings are not the sealing point, the flare is. 

Check t be sure your flares are not cracked.  The crack could be in the flare itself or in the tubing directly behind the flare.  If either of these are present you must cut the tubing back and re-flare it or replace the whole piece. 

[gouldsom]

Try some soap, yes soap. Rub a block across the thread, before you screw it in.
Works a treat, well it did on my worn tri power fittings.

[76eldo]

Th Teflon is more of a lubricant like the soap in this instance but also has some sealing properties for the threads.  If all of the fitting are in good shape and can be drawn tight enough you should not need anything. I don't think the factory used anything.

Use a proper line wrench and just make the fittings a little tighter than they are now. Even a quarter turn can make a difference. I like the soap idea, could a drop of oil or two do the same thing?

Brian

[TJ Hopland]

I have seen it more than once recently where its the whole fitting on the pump itself that seems to have the leak.  I'm not sure how that fitting is installed but it seems like they are not as good as they used to be so you really have to be sure you don't put any stress on them when you attach the line.

[Scot Minesinger]

This has happened to me on my 1970 after a fuel filter change.  The compression fitting makes the seal, so no tape on threads is going to fix it.

There is a rubber donut seal that with a cross section of an "L".  If you have it upside down it will leak as if it is coming from bad thread seal.  Turn it right side up and you should be good.  If it is missing then that is it.  Goes on bottom of fuel filter.  This may not have been present on original fuel pumps, but it is on newer replacements.

[chrisntam]

My understanding of different kinds of automotive fluid connections is that there are 3 main types (that I know of):

1) Flare - used on brake, fuel and transmission lines.
2) Pipe thread - used on fittings that carry liquids (fittings screwed into the block/water pump that a hose would connect to) like water temp senders and oil pressure sending units.
3) compression fittings - Those are used to connect lines like mechanical oil pressure lines.  A ferrule is compressed around the line and within the fitting when it is tightened.

For the flare fittings, the seal is made at the flare (as said previously).
For the pipe thread, the seal is made at the threads.
For compression fittings, the seal is made at the ferrule

Some use a combination of fittings, for the turbo 400 fluid lines, a pipe thread fitting is screwed into the transmission, then the line itself uses a flare fitting.  Could be the same on a fuel pump.

Others can chime is to further clarify or correct as needed.

["Cadillac Kid" Greg Surfas 15364]

Seth,
You have gotten a lot of valid suggestions, but I would like to ask exactly where is the fitting leaking.  Is it on the fitting that holds the fuel filter into the pump, or is it on the fuel line that installs into the fuel pump retaining fitting?
Both of those are difficult to reach and they often get cross threaded.
Greg Surfas