Confirm that both the hot and cold water supply valves are fully open. If the valves are closed or partially open the washer won't fill or will take longer to start the wash cycle.
Highly Likely
02 - Washing Machine Heating Element
Many washers use a heating element to raise the temperature of the water entering the tub. A defective element may cause the washer to take too long to clean its load. You can use a multimeter to test the heating element for electrical continuity. If the element tests negative for continuity, you'll know the heating element is faulty and will need to be replaced.
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The water inlet valve opens to allow water to enter the washing machine. If the water inlet valve is defective, the wash may fill slowly or not fill at all. The water inlet valve requires sufficient water pressure to function properly. First, check the water pressure to determine that it is adequate. If the water pressure is adequate, try cleaning the screens inside the water inlet valve hose connection ports. If the washer still fills slowly, replace the water inlet valve.