Fuel plumbing questions.

[ikiller]

I need to run a return line and make my supply line EFI ready, but I have been a bit confused as to the differing plumbing techniques. Most of the connections in my fuel system are barb style (FPR, Fuel Pump, Fuel Rail) so most of my plumbing connections require going from hard line to hose. I don't like the AN stuff since it requires too many adapters to go to a barbed connection (and the fittings are really pricey).

After a bunch of research I am planning on using aluminum hard tubing, and using a double 45 degree flare on the end of that to go to brass hardware store plumbing fittings. From there it is easy to end up with a brass barbed fitting to the rubber hose. Does this system sound safe enough for high pressure fuel lines? After thinking about it it seems that it should be as safe as the AN 32 degree flare with aluminum fittings as sold for hotrod and racing use.

What do you all think? Am I asking for trouble/fire? It seems safer than using compression fittings, and I should be able to make the double 45 degree flare in aluminum with an inexpensive flaring tool (as opposed to steel or stainless which require more expensive tooling).

[usagoal]

I don't know the values off hand, but some systems (depending on equipment used) can reach very high pressures. I would feel alot safer using something like a flare fitted system. Are the barbs removable on your setup? If they are you can buy an array of adapters that will go to flare. This is one part of your MS project that you shouldn't skimp on, even if it costs a couple of bucks it's better than catching the car on fire or worse. Would you be willing to have a competent welding/fab shop weld in a bung on your fuel rail to adapte to a flare fitting?

[ikiller]

I am stuck with the barbed fittings for sure and I am OK with that. The project car is a Volvo 122 and many of the parts are from later fuel injected models (D-jet). The fuel rail, injectors, fuel pressure regulator (from a datsun), and fuel pump all have built in non removable barb fittings. Since they were originally designed for this purpose I trust they will be OK with some nice quality efi hose clamps.

My main concern was about the use of 45 degree double flare on aluminum tubing in combination with brass plumbing fittings. I couldn't find any references to anybody else using this setup and I was looking for a sanity check. I read of some guys just putting a bubble flare on the end of the line and slipping the hose directly over that with a clamp.

[Jack]

The injectors on my manifold (mid-80's Rover) use hoses over smooth pipe. It's only a 36 psi system, but a smooth pipe is a lot different (more apt to leak or slip) than a barbed fitting.

Use the correct injection hose and clamps and you should be fine.

jack

[PSIG]

... Since they were originally designed for this purpose I trust they will be OK with some nice quality efi hose clamps.

True. Bosch even created the clampless system for FI fuel with push-on hoses, although many add clamps for peace of mind. If you ever use push-on be sure to use the correctly matched nipples and hose. Even the big-time US race hose makers are doing push-on now... 40 years later.

... I read of some guys just putting a bubble flare on the end of the line and slipping the hose directly over that with a clamp.

That is very common. Minimum R9 rated hose in EFI systems. Whatever you use, you can test to full pressure by deadheading the return line at the tank until you get full pressure, then shut the pump off and go look for leaks. Test everything.

[Jack]

Whatever you use, you can test to full pressure by deadheading the return line at the tank until you get full pressure, then shut the pump off and go look for leaks. Test everything.

Great idea PSIG. It takes the regulator out of the equasion and allows full pressure. I should have though of that one myself.

Jack