Porsche 911 engines need a steady supply of fuel at the correct pressure for good performance. If the hum from your fuel pump is getting louder, it may be a sign of imminent failure. When you order your new fuel pump, be sure to get two new copper sealing rings. (Figure 1) Here is how to replace it:
The first step in doing any work where the fuel system will be opened is to position the car away from any possible sources of ignition, such as a gas water heater, because you are likely to spill some fuel. Next, place the front of the car up on jack stands. (Figure 2) You need some room to work under the car, so the car should be near the maximum HEIGHT of the jack stands. I usually place them as shown (Figure 3), with a piece of wood to protect the car.
The fuel pump is located above the splash panel between the front wheels. To remove the splash panel, take off the two 17mm nuts, and the two 8mm allen-head bolts. This panel is a bit heavier than it looks, so be sure to support it when you take off the fasteners. (Figure 4)
To remove the fuel pump, disconnect the two electrical wires, taking note of which is positive and which is negative. Then unscrew the 19mm cap nut that holds the fuel outlet line (you may need to counterhold this fastener with a 15mm wrench). Loosen the hose clamp holding the fuel pump, and you are ready to take off the pump. Loosen the clamp holding the fuel input line, remove the pump, and replace it with the new pump. You will need to work quickly during this part of the procedure to prevent spilling a lot of fuel (Figure 5).
Use two new copper sealing rings, one on each side of the banjo fitting, when replacing the fuel outlet line. Reattach the wiring, making sure that the positive and negative wires are correct. Tighten the fuel inlet line, and replace the sponge piece next to the fuel pump, which is a sound deadener. Replace the splash pan, and you are done.
PLEASE NOTE: The fuel pump on the 964 C2/C4 is NOT located under the front valence like prior 911 models. The fuel pump on the C2/C4 is located on the passenger side under floor area just behind the front diff C4 and the fuel tank. You need to remove a steel cover plate to access the fuel pump. This is best done on a lift but might be possible on jack stands. Expect to get a bath of fuel if not on a lift. You can pull the DME relay and jumper terminal 30 and 87b - per the Porsche service manual to test the fuel pump.