91 D21 wont turn over

[Queball8]

Truck has had issues in the past. It is a 1991 D21 4cylinder auto with air, the truck will not shift into gear without pulling the shift lock switch on the left side of the collum. This process has been ineffect for around a year then a couple of weeks ago the truck would intermittently not turn over then all of a sudden it would. Any suggestions would be appreciated Matt