Mowed awhile ago and finished, put the mower up. My neighbor was going to borrow it but it wouldn't start. It had gas, spark & was turning over. JD told me to check the carburetor solenoid. I did and it was gummed up so I replaced it and the mower fired right up. I used it all summer and finally it did the same thing. I replaced the fuel filter, fuel pump and carburetor. Got done and fully expected it to start right up. Nothing. Got gas, spark & cranking but won't start. Now in the process of this calamity it has now completely stopped turning over at all. TIA for any suggestions