It is possible for your car to hesitate upon acceleration or idling after a Fuel Pump replacement. This could be due to several reasons and might not directly point to a defective replacement part. It could be because the fuel system is not properly primed post-replacement of the pump. For instance, most new vehicles have a fuel pressure regulator that is used in collaboration with the Fuel Pump to set a constant fuel pressure; in most gasoline engines, the pressure ranges between 40 and 60 psi. Hesitation or rough idling occurs when the fuel system is not properly primed, leading to air bubbles in the system.
A study by the Automotive Diagnostic Institute estimated that 15% of fuel system failures post pump replacement were due to incomplete priming or air pockets causing poor fuel flow to the engine. Additionally, if the Fuel Pump itself was not the problem but a clogged fuel filter, lines, or injectors, replacing the pump would not resolve the basic cause of the hesitation. In fact, according to AutoZone, a clogged fuel filter can restrict fuel flow and cause hesitation even after the replacement of a Fuel Pump.
Another possible cause is a problem with the fuel injectors. If these were not checked at the time of replacement, they could be clogged or faulty, which will lead to poor fuel atomization and hesitation in the engine. According to AAA, 30% of the problems in the fuel delivery system are due to clogged injectors, which can be aggravated by a faulty Fuel Pump.
In some instances, replacement of the fuel pump can inadvertently cause problems with the car’s ECU or Engine Control Unit. The ECU takes a reading from sensors that monitor fuel delivery and makes adjustments in air-fuel ratio, timing, and idle speed. If the new fuel pump is not of the same specifications as the original, or if it was installed improperly, the ECU may not adjust those parameters well enough, hence leading to hesitation or stuttering. In fact, Ford had a similar problem with their 2016 Focus models, where poor installation of the Fuel Pump resulted in the ECU not being able to properly control the flow of fuel after the pump was replaced, leading to hesitation and poor performance.
It is also very important to ensure that the replacement Fuel Pump is of good quality and suitable for the vehicle. According to Consumer Reports, low-quality Fuel Pumps or those not made to the specifications of the OEM can also fail miserably-even those that are brand new. Low-quality Fuel Pumps may deliver inconsistent fuel flow, thus causing hesitation upon acceleration. This actually happens to many drivers who replaced a Fuel Pump with an aftermarket unit, wherein performance does not meet the same standard as the original part.
Another probably overlooked cause is a bad fuel pressure regulator. When this is faulty, it won’t allow fuel to flow appropriately in the system, hence leading to hesitation. In instances, replacement of the Fuel Pump may mask this problem but later lead to hesitation and other problems. A fuel pressure regulator that cannot maintain the required pressure, usually between 30 to 45 psi for most vehicles, will result in engine hesitation, particularly when accelerating.
Lastly, incorrect installation of the Fuel Pump may result in a number of problems. A Fuel Pump has to be installed exactly according to the manufacturer’s specifications; otherwise, misalignment or poor fuel delivery could occur, which causes hesitation. For example, if the Fuel Pump is not installed properly in the fuel tank or if the electrical connections are not fully secured, then the fuel system will not work as it should, creating hesitation during vehicle operation.
The reasons a car could hesitate after a Fuel Pump replacement include faulty fuel system priming, clogged injectors, malfunctioning ECU, wrong specification of pumps, or poor installation practices. In order to avoid these problems, the correct, high-quality Fuel Pump should always be chosen for your vehicle, and it needs to be installed by a qualified professional. For a reliable, efficient, and high-performance Fuel Pump, visit Kemso Fuel Pumps for top-quality products designed to meet OEM standards.