Starter issues again

[Jbevs]

I know the fender solenoid is good, occasionally the starter won't turn over unless I go down and wiggle the wires on the starter solenoid. The connection are clean and tight. The area where the motor meets the engine is covered in oil. Could this cause a grounding issue? What can I check for? Other grounds to look at?

 

[7.3 powerstrok]

i f the starter is bolted tight the oil should not be the problem ,sounds to me the solenoid itself or the connections to it .