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Ok, now we're going to run the return fuel lines for the system. These are 6AN lines and are under low pressure compared to the feed lines. I started these at the rear of the car just like the feed lines. Using basically the same steps, accept I altered the route a bit.
First thing I did was determine how I wanted to plumb the return line back into the fuel tank. There are many options out there including customized sending units that have both a pickup and return line for 65-70 Mustangs. I opted for the simple approach and utilized the techniques set forth in the instructions from Mass-Flo EFI. I determined a good location in the trunk to drill a hole that will feed the fuel return line back to the filler neck . Mass-Flo EFI provides you with a bushing that can be welded into the filler neck and accepts an AN to NPT fitting provided with the kit. I drilled the hole installed the bushing in the trunk pan. I then test fit the section of fuel line that would run from the fuel pressure regulator in the engine bay all the way back to the filler neck in the trunk. I chose to run from the regulator down the firewall, toe pan, and under the floor parallel with the feed line.
Then rather than stay on the inside of the subframe connector, I decided to run along the lip under the rocker panel. At the rear of the car I stayed on the outside of the rear frame rail and ran up along the wheel well following the rear frame rail. Just rear of the bump stop I installed the "T" fitting that is unique to the installation of the Accel pump. This allows the pump to be "self-priming". The line continues from the "T" to along the wheel well, throught the hole in the trunk and is connected to the filler neck.
I then ran the breather line from the "T" fitting over the exhaust and rear sway bar down to the fuel pump. It attaches to the bottom of the pump via a small 1/4" NPT fitting. I purchased a 1/4"M to 1/4"F NPT 90* elbow to allow me to keep the breather line up and out of harms way. Otherwise you'll have a loop of 6AN fuel line hanging very low under your car. Not a good idea. Then it was back to the engine bay where I installed the fuel pressure regulator and connected it to the feed line. The picture shows the regulator connected to the fuel rail, but at this time I didn't have this line installed. The regulator was mounted to the rear inner fender using the supplied bracket and hardware.
