Now that you've suspected the fuel pump is bad, you're only steps away from determining the severity of the problem. Symptoms can include your car failing to start or accelerating poorly. How you troubleshoot the problem depends on what type of fuel pump is in your car. Whatever the case, there are other parts to diagnose before investigating the fuel pump. Even if the pump is bad, a basic replacement is all it will take to get your car in better shape.
Determine pump type. Your troubleshooting the fuel pump depends on whether your car has a carburetor- or fuel-injected (EFI) system. If the EFI, you'll most likely need to perform an electrical test with a multimeter. Check your vehicle's manual to determine what system is in your vehicle.
Compare symptoms. A poorly-functioning fuel pump may cause hard starting, poor idle quality, hesitation or stumbling when accelerating, and a loss of power at higher speeds. And if your car fails to start completely, then your fuel pump may be the culprit.
Consider past maintenance. Check whether you or a previous owner had ever changed the fuel filter. If it was never changed, and you're experiencing poor engine performance rather than a failure to start, start by changing the filter. Check your owner's manual or a corresponding repair manual for the procedure.
Check basic functions. If your car has an electric fuel pump, you may have a simple electrical problem and not a pump problem. Check for a blown fuse in the fuse box, as well as for insufficient battery voltage. Also, check the wiring to and from the pump to see if there's a loose wire.
Do a pressure test. Tap a pressure gauge into the fuel supply line with the engine off, but the fuel pump energized (electrical system on). Another test -- a fuel flow test -- doesn't require a pressure gauge. In this test, disconnect the fuel line while the engine is off. Energize the pump and allow the fuel to be pumped into a container. Measure the flow and compare with the proper specs.
Perform an electrical test and measure amperage. Connect one multimeter lead to the positive battery post and the other lead to the hot wire of the fuel pump. Check a service manual for exact procedure, and compare the measured amperage with what's normal for your fuel system. If the reading's too high, your pump is bad.
