Indeed, a faulty Fuel Pump can cause high engine idle, though this is not the most common symptom. The Fuel Pump is very important in maintaining proper fuel pressure in the engine, usually between 30 and 50 PSI for most vehicles. As the Fuel Pump starts to fail, it may not be able to keep up with the required fuel pressure, which then causes an imbalance in the air-fuel mixture of the engine. This will cause an imbalance that can lead to higher-than-normal idle speeds. A high engine idle would mean that the engine is balancing the irregular fuel delivery by increasing the throttle to keep it running, thus keeping the engine RPMs high even at a standstill.
The Society of Automotive Engineers conducted a study where, out of a hundred, 15 percent of problems in engine idles were rooted in fuel delivery issues brought about by such components as a faulty Fuel Pump. For instance, if the fuel pump is degrading then it may not pump adequate fuel while at idle, which prompts the engine’s control system on idle to act by lifting the RPM so that there is compensation due to the lean fuel mixture. This will result in an idle speed that is 200-300 RPM higher than normal.
Besides this, a faulty Fuel Pump can cause erratic power delivery, which may result in the engine hesitating or surging; both of these can also contribute to abnormal behavior on idle. If the pump is weak, it may not support adequate pressure during idle, which eventually drops the performance of the engine. This could cause an automatic increase in the idle speed for compensation. High idle speeds would, therefore, be worth investigating for symptoms like stalling, rough idling, or poor acceleration.