Fuel System

A EFI fuel system differs from a carbureted setup. First is the pressure. A carb operates at 5-7 PSI. EFI at 43-50 PSI. This means special hoses have to be used. Next is the fuel pump. A mechanical pump can not supply the pressure needed, so an electrical pump is requiered. Electrical pump need to be mounted close to the fuel tank. Finally, a EFI system needs a return line for the unused fuel. The pump operates at full speed at all times. A AFPR (Adjustable Fuel Pressure Regulator) is mounted on one of the fuel rails. The AFPR regulates the pressure and sends unused fuel back to the tank. This mode of operation has some advantages. First, the constant fuel flow means the fuel will be much cooler. Fuel will not sit in a line, moving slowly towards a carburetor, being heated by exhaust and engine. Next, the flowing fuel cools and lubricates the pump, ensuring a long and happy life. In the process, vapor lock is completely eliminated.

I started out by installing the fuel pump and pre-filter. The pre-filter filters out bigger chunks of dirt to protect the pump. It is rated at 73 mikrons. There is also a main fuel filter that I will mount in the engine compartment that protects the injectors that is rated at 10 mikrons.

I mounted a regular transmission mount on the frame rail, and then made a aluminum bracket that I bolted the pump to. The reason for the tranny mount is to isolate the pump as much as possible for noise reasons. At $6 you can't beat a tranny mount for this task.

Here you can see how the stock sender connects to the pref-filter, then goes to the pump via a hardline that was made out of 3/8" aluminum tubing found at most hardware stores. The pump clamp came with the kit, and is bolted to a bracket I made out of 1/4" thick, 1" wide aluminum. All hoses are special Fuel Injection hoses with a 100 PSI working pressure, and 500 PSI burst pressure rating.

Next was the return line. This is where I ran into a serious snag and what was supposed to be a 5 minute hooking up of a hose turned into a 6 hour project. The problem was that the vapor line that I thought was 5/16" hardline turned out to only be 1/4". The minimum for a return line is 5/16". So after some carefully chosen words it was off to the hardware store to get 15 feet of 3/8" aluminum tubing. I then ran the new tubing alongside the vapor line on the drivers side frame rail all the way from the tank to the engine compartment.

Here is a picture of the new line on top of the drivers side frame rail. Rubber covered clamps were used to hold it in place.

This picture shows the difference in the thickness of the vapor line and the new 3/8" hardline. You can see the vapor line to the right on top of the frame rail, and to the left is the new line with a hose to the tank. Surprisingly the fitting that goes into the tank was a full 3/8". If it had been 1/4" as well, I would truly have been screwed.