Fuel lines - single or double flare?

[Kestas]

I need to splice in a section of fuel line to repair some rust perforation. Must the ends be double flared or will single flare suffice? The car is a fuel injected 91 Mergury Grand Marquis.

 

[StressSolutions]

I'd use compression fittings.

 

[labman]

Gasoline is tough to seal. Use double flare.

 

[mechtech]

I'd use compression fittings, and we do so all the time in the shop.

 

[TheLoneRanger]

Kestas, do a double flare on mild steel lines. Stainless steel is the only one you can get away with using a single flare.

Make sure your tubing cut is clean and square, and deburr the edges. Then use a drop of oil on the flare tool, and you'll get a perfect flare every time.

That fuel line is probably in two sections, so you might be able to replace an entire section fairly easily.

 

[Kestas]

Fairly easily?? That fuel line is a single piece that runs from the engine to the fuel tank. It is behind the body mount structure. Essentially, they built the car around the lines!! It can only come out in pieces. I plan on replacing only the badly corroded section.

Of the two fuel lines that run the length of the body (one on each side), I've already experienced three areas that have perforated. One has a patch that's held for two years. The last repair took me a whole day. I used double flares, but I was hoping I could get away with single flares. I use never-seize to lubricate the flaring process.

Why can you get away with a single flare on stainless steel lines? Stainless doesn't necessarily make a steel stronger.

Thanks for the thumbs-up for compression fittings. I may use it.

 

[TheLoneRanger]

quote:

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Fairly easily?? That fuel line is a single piece that runs from the engine to the fuel tank. It is behind the body mount structure. Essentially, they built the car around the lines!!

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Ha ha, well I may have over-simplifed; my recent vehicles have all been trucks with the fuel lines attached to the inside frame rails, easily accessable.

Stainless is harder and a bit more brittle than the stock lines, and in fact it's not recommended to double flare SS at all. If it is, cracks tend to form at the flares.

It sounds like those lines are are in poor shape. Maybe you could route a new line, leaving the old one in place? That is, if you can find terminating points at the tank and engine? Compression fittings are not recommended for brake lines, because of the extreme pressures, but for fuel lines they may be acceptable.....

 

[Kestas]

The kicker is that this car was rustproofed (by myself) since Day 1. It's corroding in the shadows of the rustproofing. Next time I'll know to be even more dilligent (even though mechanics have praised my rustproofing work).

The fuel line terminating points have shrink-fit tubing and spring-lock couplings... a weird design that makes for easy assembly at the plant. I've taken apart spring-lock couplings before, but these just DO NOT WANT TO BUDGE!... even with PB Blaster, and they're in tight spots! It's simply easier to cut away the rotted section and splice in new fuel line. That, or remove the body off the frame for access!