Maytag neptune starts to fill with water then stops

since you can drain it
take off the back and watch what happens when u turn it on
i believe you make have a loose drain connection

If your machine is a FAV6800AWW or FAV9800AWW the (upside down u and f) may be a “NF” for no fill error. The washer has tried to fill the machine with water and has sensed a water fill issue. The control board has shut the wash cycle down with an “NF” error to the display because of excess time to complete the water fill portion of the wash cycle.
Will the machine complete the cycle with Hot water only or Cold water only? I would do a Quick Wash cycle just to test with an empty wash basket.
Regardless of the above test and assuming you have good water pressure for both Hot and Cold supplies to the washer I would do the following. Close the water source valves to the washer and remove the Hot and Cold hose connections at the back of the machine and check for clogged inlet screens. If the water inlet screens are free of restrictions I would go into Service Mode and turn on the Hot and Cold water valves on one at a time and make sure the tub will fill with about 2 inches of water in about 3 minutes in service mode. Check both Hot and Cold inlet valves individually see page 16 of the SM Board Output Test, enter service mode and do the function test for both Hot and Cold Water Valve’s. If the inlet screens are clean and you have water fill restrictions in service mode we may need to look at replacing the water inlet valve assembly. You can turn on the drain pump in service mode to empty the tub or just start a wash cycle and the machine will empty the tub.
The Service Manual for reference. Sears Parts Direct for reference.

A couple things may be going on here... you may not want to hear, but the Neptune has a had many "consumer related problems".

If your complaint is "will not stop filling with water" I would access your inlet water-valve (typically blue with 2 black battery looking solenoids; where your water-lines connect directly), test for continuity and replace as necessary. Sometimes inlet-water valves also go bad where the complaint is: "no water comes in at all".

Maybe a water fill problem ,washer will stop if no or not enough water enters the tub in a given time

fl is a over fill. clean the pump out and the sump near the pump is in the back the dran hose goes to it

Most likely the motor control unit, the MCU controls the timer (loop circuit). Best way to check is to just pull the MCU out and visually inspect it for burned components, although it is not always visible. You may need to make some involved voltage readings to verify.

Check the belt is still on the wheel.. may have slipped off. Take top of washer off and you will be able to see if its ok.

:o)

Check for low water pressure. Clear screens in inlet valve. Do-not remove screens. This unit will turn off if not filled in specified time.

either a faulty pressure switch / pot or faulty controller - either way you will need to call someone in.

My maytag neptune dryer quit heating, after my wife changed the temp setting on the console from regular, to extra low drying temperature. The heating element reads 10.5 ohms. The thermal cutoff reads 0.02 ohms. The hi-limit thermo reads 0.02 ohms. The power coming into the dryer is 240 volts. What can I check or need to replace.