Indirectly, the one possible effect of a faulty fuel pump is damage to the exhaust system. A fuel pump’s job is to send fuel from the tank to the engine at the right pressure. As a fuel pump starts to go bad, a pump may not deliver enough or a consistent level of fuel — meaning that combustion in the engine could be compromised. Incomplete combustion can happen, leading to unburned fuel that enters the exhaust system, which over time can cause damage.
If the fuel pump does not deliver fuel properly, the engine may misfire, idle roughly or lack acceleration. This is a technical process involving the ignition of the air-fuel mixture present in the cylinders; when the proper ignition does not occur, it is known as misfire, which commonly happens when there is no adequate fuel flow. In fact, 5 percent of engine misfires can be traced back to the fuel system, and the fuel pump, as data drawn from the National Automobile Dealers Association (NADA) suggests. The unburned fuel generated by these misfires can then make its way through the exhaust system, where it can then ignite inside the catalytic converter.
Catalytic converter The catalytic converter is part of the exhaust system that converts harmful emissions into less harmful gases. But it operates at high temperature, about 1,000°F (538°C). An unburned fuel that enters into the catalytic increases the temperature of the converter and it may get a bust. According to a report released by the Environmental Protection Agency (EPA), upwards of 10–20% of catalytic converter failures are due to engine performance problems, such as breakdowns in fuel delivery systems. If this heat persists over time, it will damage the internal structure of the converter, leading to expensive repairs or replacement. Replacement catalytic converters can range from $500 to $2,000 based on the make and model of the vehicle.
Finally, if unburned fuel reaches the exhaust and damages the catalytic converter, the unburned fuel can lower the oxygen levels in the exhaust and negatively affect the performance of the oxygen sensors (which are used to monitor the amount of oxygen in the exhaust gases). An oxygen sensor that is subpar can give wrong air-fuel ratio readings, worsening the fuel economy problems. The Automotive Service Association (ASA) estimates that oxygen sensor failure accounts for about 2 percent of all vehicle repairs, not an insignificant number, as a large share is contributed by issues in the fuel system.
If the fuel pump is malfunctioning, it can also lead the engine’s combustion not to be timed as it should be, resulting in higher levels of toxic emissions. Not only does this strain the exhaust system, but it also makes it more likely to damage the engine. If this problem goes on without being resolved, eventually the total health of the engine and exhaust system may deteriorate. According to the Automotive Aftermarket Industry Association (AAIA), 15-20% of vehicles on the road with fuel system problems will have later problems with the exhaust system if the problem isn’t corrected.
Bottom line: A bad fuel pump does not damage the exhaust system, but it does make conditions for improper combustion, misfires and excess heat which can definitely damage items like the catalytic converter and oxygen sensors pretty badly. Assuming your fuel pump is going bad, have it checked and replaced if needed so your exhaust system doesn’t need a costly repair. To learn more about premium fuel pumps, visit Fuel Pump.