i gave a 91 ranger 4x4 to my step son and it cut off on him and will not restart,when you turn the key to crank sounds like starter just spinning but it is turning,i checked for spark and it has that,i think may be the timing chain and started to remove cover to acess but cant get crank damper all way off can see the chain is in tact any help?

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1991 ranger 4x4 4.0 automatic super cab