I know I’m a bit late to the party but I thought I’d add my fuel line story. My recently acquired 90SE was still rocking the original fuel lines. After looking around at what others had done to solve this problem, I decided to go the easy route and use fuel injection hose. Specifically, I used Gates Barricade #4219BF in 5/16” size (7.92mm), and ABA #21014 clamps. I used this combo to replace all of my fuel lines, including the return line.
A few notes for those that are contemplating this route:
The workshop manual suggests disconnecting the fuel pump wiring as part of the process for depressurization of the fuel system. Instead, I pulled the inertia switch plunger as the car was running, then cranked the engine for an additional 3 seconds after it ran out of fuel.
There are two fittings that I did not remove from the engine: the fuel injection rail inlet fitting (GM says you can’t remove this one without ruining it) and the return fitting under the pressure regulator (I saw no way of removing this one). So both of these fittings had the old line cut off and the new line installed in situ.
There are 4 o-rings that should be replaced as well: 1 on each of the fittings on either side of the fuel filter, and 1 on each of the fittings for the secondary injectors. They are all the same size. I purchased a small kit of assorted fuel injection o-rings (Dorman #90100) that had a half dozen or so of the correct size.
You should replace the fuel filter as well. AC Delco #GF652.
Although the 5/16” hose works just fine for the entire fuel system, I do believe it is just a tad bigger diameter than the stock return line. I say this because it slid very easily onto the return fitting under the pressure regulator and the return line adapter at the fuel pump. Every other fitting it was a bit of a pain to push the new line on. That being said, the new return line does not leak nor are there any fumes.
Overall I’m very pleased with this solution and the total cost was about $60.