Disconnect the battery and pull the terminals off of the solenoid and clean good with a small wire brush. The large red wire on the left looks like it is almost touching the small terminal on the bottom of the solenoid, tighten it so it is pointed toward the left away from the solenoid, does it go to battery posative. You dont need to hold the camers so close! The wire that is taped does it go to the starter? You really need to clean up the engine bay and go through all the connectors and clean with electrical cleaner and use dielectric grease to put them together. Look for any bare,cracked or broken wires and repair as necessary. Sand all grounds metal to metal and bend the battery cables end to end looking for weak spots. The first thing I would do is blast it good with a pressure washer and let it dry good while cleaning all the connections and inspecting the wires especially around the exhaust manifold/s.