Hello and thanks for your question. My name is XXXXX XXXXX I will do all I can to help.
Let me first ask, Does the van crank in neutral every time? But fails to crank in park sometimes?
See if it starts in neutral normally?
no , It does no start in neutral or park until I move back and forth.
Alright, Most of the time, This problem can be solved by replacing the Neutral Safety Switch, In the start circuit, Power has to pass through the Neutral Safety Switch first, before going to the starter motor, as this switch makes sure you can't start the vehicle in D or Reverse.
The part can be obtained for 20 dollars or less, and screws into the transmission case.
Hold on just one second and I can upload the test procedure.
The switch screws into the transmission case from the front.
and only takes around 1/2 an hour to replace.
Please let me know if you have any further questions.