If a car has a faulty fuel pump, the time it takes to "warm up" or operate efficiently can be significantly affected. Here’s a breakdown in points:

Delayed Engine Start:
A faulty fuel pump may not deliver adequate fuel pressure immediately, causing prolonged cranking before the engine starts. This delay can range from a few seconds to several minutes.

Erratic Fuel Delivery:
A malfunctioning fuel pump may not consistently supply fuel, leading to rough idling and sputtering during initial operation. The car may take longer to stabilize and run smoothly.

Dependent on Severity of Fault:
If the pump is partially functional, the car may eventually warm up but with noticeable performance issues. If the pump is severely damaged, it may prevent the car from running altogether.

Cold Weather Impact:
In colder temperatures, the symptoms of a faulty fuel pump can worsen, as fuel lines and injectors may take additional time to stabilize due to reduced fuel pressure.

Load-Dependent Behavior:
Initially, the car may struggle when accelerating or under load, and it may take longer for the engine to reach optimal operating conditions.

Warning Signs During Warm-Up:
Common indicators, such as sputtering, stalling, or loss of power during the warm-up phase, can signal that the fuel pump is struggling to supply adequate fuel.

Impact on Fuel-Air Mixture:
A weak fuel pump can disrupt the fuel-air ratio, causing the engine control unit (ECU) to overcompensate and prolonging the warming-up process.

May Not Warm Up at All:
In severe cases, the engine may fail to warm up properly or shut down, making driving unsafe.

Key Recommendation:
If your car is taking unusually long to warm up and you suspect a faulty fuel pump, have it inspected and repaired promptly to avoid further damage to the engine or fuel system.