Odd fuel line fittings?

[Matt Harwood]

I'm going to re-plumb the entire fuel system on the '41 Buick this weekend, including a new sending unit in the tank. I ordered a sending unit which came with what appears to be an inverted (double) flare female fitting soldered in place. That's good, I can work with that. I also ordered a flexible fuel line that attaches to the fuel pump so the engine can move a bit. That one came with a slightly different fitting that looks like an inverted flare, but not quite, and came with a unique male fitting that isn't a standard male double flare fitting. Does anyone recognize this and what kind of flare should I use with it?

 

 

Here's the flex line with fittings. Not quite a standard inverted/double flare, but close. I don't recognize the male fitting.

 

 

Here's the flex line (left) versus what appears to be a standard inverted/double flare fitting on the sending unit.

 

There's definitely a difference, but are they both inverted/double flare? How should I flare my line going into that fitting? Any ideas?

[Bloo]

I think there is an incorrect combination of parts there somehow. Are you familiar with "threaded sleeve" fittings? I thought Buick got rid of them by 41, but maybe not.

 

I rebuilt a tank sender for a 37 Roadmaster and it had a double flare fitting that soldered on. If I remember correctly, that whole car used double flare on the fuel system. My whole 36 Pontiac was threaded sleeve (tank sender too).

 

The Pontiac, as built, used a hose about like that, and it had a threaded sleeve fitting on one end. The threaded sleeve fitting slips over the steel gas line and then the whole mess screws into the end of the hose. The fitting, once tightened, becomes part of the steel gas line and stays with it no matter how many times you disconnect it or change the hose.

 

The other and of the hose was a piece of tubing for another threaded sleeve to go on.

 

Looking at the steel gas line on your 41 where it connects to the fuel pump hose will tell the story. Is there a threaded sleeve there? Or a double flare and nut? Or nothing at all?

 

As for that hose, it just looks wrong. Does that fitting even screw into the hose right? The female half of a threaded sleeve setup is a large open taper (instead of a seat like double flare would have). I believe the threads are different on double flare as well.

 

EDIT: What does the other end of your new hose look like? Could that sleeve belong on the other end?

Edited May 12, 2020 by Bloo (see edit history)

[Bloo]

Continuing along that line of thinking, I dug out a couple of NOS/NORS Pontiac hoses. The idea being that maybe, instead of being threaded sleeve at both ends like mine, maybe yours is double flare at the chassis end, and threaded sleeve at the fuel pump end. Here you can see the threaded sleeves that were screwed into the chassis end, although in a normal replacement procedure there would already be a threaded sleeve on the chassis end, and you would use the new one at the other end.

 

 

What female threaded sleeve looks like:

 

 

Other end of the hose:

 

 

And a threaded sleeve in its natural habitat, permanently married to a piece of tubing. It shrinks and bites into the tubing. To replace it, you would have to carefully cut the nut off, or shorten the tubing.

 

 

 

Edited May 12, 2020 by Bloo (see edit history)

[Matt Harwood]

Here's the other end of the flex hose:

 

 

That almost looks like a bubble flare or reverse conical seat and there's no groove, but I am assuming that this end fits on the fuel pump and makes a seal there somehow or maybe a brass single flare male fitting. I'll take it apart and have a look later today.

 

I was thinking that the male fitting almost seems like a compression fitting, as you describe a "threaded sleeve" fitting. It looks like it compresses on the tubing and makes a seal. It appears that there's a groove for it in the female hose fitting, although I'll admit I've never seen one like that before--does that groove kind of swage the pointed end of the male fitting onto the tubing? The male fitting screws into the female hose fitting easily and seats in the groove shown in the photos in the first post. It came as an assembly, so I presume they're meant to work together. On the other hand, I bet I could use a standard inverted flare on the tubing and it would still seal--it's only dealing with 4-5 PSI in an ancient fuel system.  I'll have to go get a better look at the fuel pump, which probably has brass fittings screwed into the body so I can change them to whatever I want.

 

Thanks!

Edited May 12, 2020 by Matt Harwood (see edit history)

[Bloo]

The threaded sleeve goes in that end!

 

There is still a missing piece to the puzzle though. I can't understand why it would have what appears to be a FEMALE double flare at the other end. I would love to know what kind of fitting the chassis line has.

[Bloo]

Oh one other thing, I don't know if you can tell in the pic, but one of those hoses is outside braided in brass! I suspect (but don't have the least bit of proof) that the original hose was like that, and that the hose served as the sending unit ground. Be sure to ground your sending unit.

[Matt Harwood]

28 minutes ago, Bloo said:

The threaded sleeve goes in that end!

 

There is still a missing piece to the puzzle though. I can't understand why it would have what appears to be a FEMALE double flare at the other end. I would love to know what kind of fitting the chassis line has.

 

Awesome! That makes sense. There's a female conical seat in there that should push the fuel line into shape and make a seal. I only have the one fitting, so I don't want to bugger it up. Just seat the tubing in the fitting and tighten?

 

It looks as though the fuel line on the chassis end uses a standard double flare fitting like this:

 

 

That screws into the end of the flex line with the groove in it, correct? Perhaps it's also a double flare fitting, just a slightly different type. The seat should still compress even though the center "cone" isn't as pronounced as most female double flare fittings.

 

I'm not sure what Buick used as OEM equipment and I doubt that anything on my car's fuel system is original, so I'll have to make it up as I go. I don't mind using double flare fittings throughout, although single flare is often my preference for low-pressure fuel systems.

[Bloo]

The first pic you posted looks like a double flare fitting to me. That much makes sense. The end with the seat goes there.

 

On the other end, a piece of tubing goes in, as far as it will go (theres usually a little shelf to stop it, and the nut just tightens.  It takes a bit of force the first time, just go slow and use a GOOD tubing wrench. The current producer of those fittings says not to use them on steel tubing, but thats what was done on fuel lines back in the day, and it works fine. The end of that fitting bites into the tubing and becomes a permanent part of it. If you doubt you went far enough, you can take it off and look. The nut stays with the piece of tubing forever, and once "bit" it cant slide off.

 

The thing that confuses me is, I cant imagine what sort of fittings would be on the fuel pump that would leave a piece of tubing sticking out for that threaded sleeve to go on.

Edited May 12, 2020 by Bloo (see edit history)

[Bloo]

For what it's worth, a better plan might be to get hose barb adapters for the double flare chassis line and the fuel pump, and just hook it up with some 30r9 hose and a couple of fuel injection clamps. I did my flex hose about like that when I didn't have a stock-type hose or enough threaded sleeve fittings. I have everything now but am reluctant to change it. 30r9 is bomb proof.

[joe_padavano]

Matt,

 

The plug is from a line called Threaded Sleeve fittings. As Bloo points out, I don't think the plug is correct for that hose. These pages are from the Eaton Brass Products Catalog, linked here, pages 101 and 102. FYI, it's a handy catalog.

 

 

[Bloo]

I think he's fine if he sticks the threaded sleeve in the other end, The mystery to me is that the fuel pump then must have had tubing coming out of it to connect to that. Why would it? The pump probably would have had pipe threads, so that would mean another adapter to either double flare or threaded sleeve, and a piece of tubing. Yeah, it would work and be fine, it just doesn't make any sense.

 

Maybe the place where the hose crosses over is not close to the fuel pump. That could explain it.

[Matt Harwood]

2 minutes ago, Bloo said:

Maybe the place where the hose crosses over is not close to the fuel pump. That could explain it.

 

You are 100% correct! I went out and looked at both my car and the all-original '41 Super sitting in the showroom and both have hard line connected to the fuel pump with the flexible hose farther back. Neither car is done 100% correctly, of course, but I can get a pretty good idea of how it's supposed to be. 

 

Line coming off the Limited's fuel pump. Since I'm replacing the
fuel pump, I'll also replace this line. It's incorrect anyway.

 

Here's the '41 Super, which is a Doug Seybold car. I'm assuming that the hard line

is correct, since it's even got a little clip to hold it in place, but his flex

line secured with clamps isn't right—this is where the flex line goes.

 

It seems that I can make a new hard line from the flex hose to the fuel pump, slip on the threaded sleeve fitting, and use that to secure it to the flex hose on the pump side. On the chassis side of the flex hose, I will use a double flare fitting to connect it to the hard line, which goes back to the tank. That makes a lot more sense.

 

Thanks, guys!