How to Troubleshoot a Fuel Pump on a 1987 Porsche 944

The 1987 Porsche 944 is equipped with an electric fuel pump. The fuel pump sits inside the car's gas tank with the top of the pump sticking out. The pump connects the car's fuel lines and the gas tank, ensuring the engine receives enough fuel to run properly. Because the fuel pump is located in a place that is difficult to reach, it is important to troubleshoot whether it is working or not before you take the time to replace it.

Tools Used: Pliers, Fuel pressure gauge

Fuel Pump Troubleshooting Guide

Listen to see whether the pump is working while the battery of the car is engaged but the car engine is turned off. Put the ignition key into the ignition and turn the key one click to the right so that the battery is on. If your fuel pump is functioning properly, it will begin pulling fuel out of the gas tank and into the fuel lines as soon as the battery is activated. Perform this test in a quiet location. You can ask a friend to help you by listening for the pump as you turn on the battery.

Investigate whether the Porsche's fuel pressure is at its proper level. Attach a fuel pressure gauge to the car's Schrader valve -- the valve is at the top of the engine and looks like the air valve on your car's tires. Turn on the engine and let it idle. Read the gauge. If your Porsche 944 has a single overhead cam engine, the pressure should be 29 psi; if your Porsche has a dual overhead cam engine, the fuel pressure should be 48 psi.

If the fuel pressure gauge shows that your fuel pressure is too high or too low, check to see whether the fuel pressure regulator is causing the problem rather than the fuel pump. The regulator is near the top of the engine block and is attached to a black fuel line. Leave the fuel pressure gauge connected to the Schrader valve and let the engine idle. Lightly squeeze the fuel line running to the fuel pressure regulator and watch to see how the fuel pressure gauge reacts. If the gauge begins to read an acceptable fuel pressure level, the regulator must be replaced before you install a new fuel pump.

Check to see if your Porsche is exhibiting signs that the fuel pump has failed. Two important signs to watch for are the engine refusing to start and the engine stalling when you press the gas pedal while driving.

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