The 390 was one of Ford's most widely used big-block engines, and was equipped in both passenger cars and trucks. All 390s used a single-action, sealed fuel pump. Because these pumps were sealed, they could not be adjusted or even repaired. Although poor fuel pressure is symptomatic of a defective fuel pump, fuel leaks are the most common symptom of a defective fuel pump on a 390. Fortunately, installing a new fuel pump on this engine is fairly straightforward.
Loosen the clamp on the tip of the negative battery cable with wrench, then pull the cable off of the battery.
Disconnect the rubber inlet line from the bottom of the fuel pump. The inlet line fits onto a metal nipple on the pump, and is secured with a single clamp. Loosen the clamp with either a nut driver or flathead screwdriver, then pull the line off of the pump. Insert the tip of the line into a plastic bag, as a small amount of gasoline will likely drip from the line.
Disconnect the metal outlet line from the bottom of the fuel pump. The outline line features an in-line nut at its tip, which screws into the fuel pump. Turn the nut in a counterclockwise direction with a wrench until the tip disconnects from the pump. Insert the tip of the line into a plastic bag, as a small amount of gasoline will likely drip from the line.
Remove the two bolts located on either side of the fuel pump with a socket wrench, then pull the pump off of the engine.
Wipe down the opening on the side of the engine that the fuel pump bolts to with a rag and engine degreaser. It is important that any old gasket material be removed from this surface so that the new fuel pump gasket will adhere to the engine properly.
Apply gasket sealant to one side of a new fuel pump gasket, then press the gasket into place on the engine.
Apply gasket sealant to the remaining side of the new fuel pump gasket.
Press the replacement fuel pump against the gasket, then install the pump's two retaining bolts with a socket wrench.
Tighten the in-line nut at the tip of the metal outlet line onto the bottom of the fuel pump.
Press the tip of the rubber inlet line onto the metal nipple on the bottom of the fuel pump, then tighten the line's clamp until the line is secure.
Reattach the negative battery cable to the battery by tightening the nut at the tip of the cable with a wrench.
