SL6 will not start with the key.

PastalliantValiant said
It was a bad wire from the relay to the starter. ..

gee, hope Redfish is listening

As for your thump, IF it's the pump area, I'm not familar with /6's Does it use a separate drive cam bolted on? could be loose. Pushrod? Could be worn. Yup, could be pump. Easiest is to pull the pump off and run a short time to find out