Fuel pump problems can leave you stranded, simply because cars won’t run without an adequate fuel supply. Most of today’s cars are fuel-injected for optimum performance and lowest emissions. Fuel is pumped from the tank to the injectors, which then spray the fuel into your engine’s cylinders. Fuel pump problems can be difficult to diagnose. You can test your fuel pump with a few special tools, but replacing a pump is probably best left to your mechanic.
The fuel pump’s job is simple: deliver fuel to the injectors. There are two requirements that the fuel pump must meet. First of all, fuel has to be delivered at the proper pressure so that the injectors will work as designed. Second, a specific volume of fuel must be delivered. How much fuel is required will depend a lot on how fast the car is going and how much load it is under (for example, is it going uphill or down).
When you car has fuel system related problems, it’s sometimes difficult to determine exactly what is at fault. Fuel pumps usually die somewhat gracefully. That is, they often fail, then start working again. It’s sort of like a warning. However, if you don’t hear what your fuel pump is telling you, then you might think it’s just a temporary problem. Lack of fuel can also be due to other factors, like a clogged fuel filter or clogged fuel lines. Injector failure can also mimic fuel pump failure.
To test your fuel pump, you’ll need a fuel pressure gauge and some adapters. Follow the gauge’s directions to connect it to your car’s fuel rail (this is under the hood, the injectors are attached to it). When you energize the pump (turn the key), the gauge should register the correct pressure. Also, that pressure should drop only slowly when the pump is switched off. A complete lack of fuel pressure probably indicates a failed fuel pump. It’s also important to test the volume of fuel delivered. This is done by connecting a hose to your fuel rail and pumping fuel into a container. A certain amount should be delivered in a certain amount of time. Check your car’s manual for the specs.
Most fuel pumps in today’s cars are located inside the fuel tank, which makes repair a little dicey. In most cases, it’s best to let a mechanic handle this job unless you have the necessary tools to lift the car and lower the gas tank.