Karl's description is spot on. You can test the button without removing it or it's wire with a multi meter easily. Ground one lead from the multi to a known good ground and touch the other wire from the multi to the chrome bezel. With the button depressed you should have a very low number or zero on the multi-meter. This will tell you if the switch is properly grounded. To check the switch, move the multi wire from the known good source to the start button terminal on the solonoid.
