Usually, drivers are shocked by the high cost of replacing the fuel pump when the fuel pump goes bad, and wonder if they get scammed. If you own a late model fuel injected car, typically the fuel pump assembly is replaced as a complete unit, rather than just the fuel pump replacement. The assembly is located INSIDE the gas tank, and you have to empty and remove the entire gas tank to replace the fuel pump module. Before we dive into the cost of replacing fuel pumps, let’s take a look at why they go wrong and what goes into replacing.
If you really want to quickly kill your fuel pump, simply run your car off gasoline. One of the main causes of fuel pump failure is running out of gas. Car manufacturers rely on your tank’s gasoline to cool the electric motor that spins the impeller for the fuel pump. When you run out of gas the engine will overheat. Moreover, it begins to suck in the last bit of gas in your tank and that gas will contain dirt and grit that has been deposited at the tank’s bottom over the years. Sure, there is a filter on the fuel pump to keep the crud out, but if you let it run too far, the pump’s suction is strong enough to pull the crud in. If you run your car with less than 1⁄4 tank on a routine basis, you are at risk of an early failure of the fuel pump.
There are other reasons for the failure of fuel pumps though. The fuel pump module includes the fuel pump, a control valve, a pulsation damper, a post-pump fuel filter and a fuel level sensor. The check valve is designed to keep the fuel line under pressure when the engine is shut down. This way, as soon as you turn the switch, pressurized fuel is ready to go. Fuel line pressure is normal to fall around 5-psi when the engine is shut down. But if the test valve goes wrong, all of the fuel will flow back into the tank and you will endure long crank times as you try to start the engine after it is sitting down. Sadly the test valve is not sold as a separate item by car makers. Even if they did, the gas tank would still have to be emptied and removed by your mechanic and the entire fuel pump assembly removed to replace the control valve.
A defective pulsation damper can cause noise to the fuel pump and a clogged post-fuel pump filter can put extra pressure on the fuel pump and cause early failure. Finally, a bad fuel pump relay, fuel pump flow control module or bad fuel pump ground causes a voltage drop which can overheat the windings of the motor and cause a failure of the fuel pump.