(Whirlpool MDB122RFS0, circa 1997)
The dishwasher makes noise as usual, but no water enters the machine (so of course it does not clean.) The interior is dry.
I checked the float for free movement, and it moves.
I checked underneath the machine and the electrical switch is properly triggered by the plunger from the float (switch clicks as float moves up and down.)
The switch does open and close electrically as tested by a meter.
I could not hear the inlet water valve open or water flow. I verified water is getting to the valve, and deduced the valve had either stuck closed or the solenoid that actuates the valve had failed. I replaced the valve/solenoid assembly. 
No change in symptom. 
I measured the voltage to the solenoid by disconnecting the electrical plug from the solenoid and testing the voltage on the plug while the valve should have been open. I get about 9 volts. (0v when valve should be closed.)
I think this is low, since the solenoid has 110v stamped on the bracket. However, I have no idea why the voltage might be dropping like that, while the rest of the system seems to be fine. Am I correct that this should be 110v, and if so what do you suggest?
I’d expect 110 there also.
It’s time to trace wires backwards to the controle module. If you can trace them back to the timer and unplug them from the timer, check the voltage there. If it’s 110, you’ve got bad wiring. Still 9? Probably a bad control module.
Time to evaluate your choices. You probably can still get repair parts for the machine. Fair warning - timers are expensive - $100 for the part would not surprise me. Seven years is often the cut-off point for stocking parts, though, so it may be hard to find unless it was used in a lot of Whirlpool’s products. (not to mention Frigidaire, Kenmore, Kirkland and KitchenAid - all made by Big W) And, after you replace the timer, you still have a seven year old dishwasher. What’s the next failure going to be?
I’d bite the bullet and get a new dishwasher, myself.