69 Mustang EFI Fuel System

Putting the EFI 5.0L HO engine out of an 89 Mustang into my 69 Mustang obviously required major changes. The biggest challenge wasn't the electrical system, but the fuel system. The old system essentially consisted of a tank, a line, a pump, a filter, and a carburetor. The newer system is much more complicated and all that is being reused from the old system is just the fuel tank. The new system runs a much higher fuel pressure and also requires an additional fuel line to return fuel to the tank from the pressure regulator.

To make matters more complicated, the original tank isn't baffled and the engine can be starved for fuel during a turn when the tank fuel level is low.

One method of dealing with this problem is to use a surge tank:
Link: EFI Surge Tanks

The low pressure pump is a Carter P4070. Here's the bracket we made to mount the pump and fuel filters.



We initially were going to put the tee fitting for the return on the low pressure pump side of the surge tank, that's why there is so much space between the two. Later we decided to put the tee on the other side of the tank. Hopefully, this will ensure that under normal operation the warmer fuel being returned from the engine would be returned to the main fuel tank and not end up in the surge tank. If we were to do this again, we would move both the surge tank and the pump inboard a few inches. It would give more clearance with the exhaust system.



We bolted a mounting loop to the bracket to hold the primary fuel filter and bent some steel tubing to go from the filter to the low pressure pump. Here's our initial setup:



We drilled a hole in the stock sending unit and brazed in a return tube, but there are doubts about the reliability of this method. A better solution would have been to drill a hole in the tank near the sending unit and use an AN fitting. By being near the sending unit, one should be able to get to the back of the AN fitting to attach a nut.

The engine fuel rail has two spring lock connectors, one for the pressure line and one for the return. Russel makes adapters to attach an AN fitting to the factory fuel rail:





Here's a little more information about spring lock connectors...
Link: Ford Spring Lock Connectors

Our high pressure pump is a Walbro GSL394. It's inlet and outlet are M10X1? internal threads. It requires a 20A fuse, according to the information stamped on the pump itself.