A bad sensor should turn on the check engine light. You should have the PCM scanned for codes.

I reread the post, and I am not sure if the mechanic has verified that your problem is due to lack of spark or lack of fuel.

 

My mechanic initially diagnosed a weak spark so he recommended replacing the distributor, and ignition coils. I picked the car up in the late afternoon and it started up. Drove it home where it sat in driveway overnight and in the morning it wouldn't start. He then replaced the "relay". Picked it up after work and in the morning it wouldn't start.
Now, after replacing the timing belt and crank sensor (yeah you guessed it) it wouldn't start at first. I tried it again and it "coughed" over and then stalled. After it stalled it refused to start again. I called a tow truck. tried to start it right before it was loaded onto t he truck. It cranked but would not start. Towed it the 2 miles to my mechanic,1/2 hour later (still before 9:00AM) and tried it then, and it started although not "crisply". Turned it off and tried again and it kept starting. When I asked if it could be related to fuel pressure or the fuel pump, the mechanic goes back to the weak spark diagnosis. I left it with him in the hopes they can figure something out, but Ive done that before and it hasn't gotten me anywhere. I'm afraid I'll have to trade it in and take a bath on it.

 

Either borrow a timing light or drop the car off at the mechanic and have him put a timing light on it before he tries to start the car.

When the car is not starting, the timing light will not flash if you have weak/no spark. If the timing light flashes, then something is up on the fuel side of things.