It is possible that the timing is off. Remove the harmonic balancer from the crankshaft and check the key and key-way. if either is damaged it can allow the spark timing to move making it almost impossible to start but it will fire every so often just not run.
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It is possible that the timing is off. Remove the harmonic balancer from the crankshaft and check the key and key-way. if either is damaged it can allow the spark timing to move making it almost impossible to start but it will fire every so often just not run.