The way i read it
"all leads disconnected." = disconnect the welding leads
" Jumper across the 2 screws on the oil pressure switch," = run a jumper wire to the 2 screws on the switch
"if the machine idles down your oil pressure switch is faulty." = if your machine idles down,replace your oil pressure switch and your idler switch should work!
If I'm wrong, sorry but i only offered my opinion on what i think KSellon meant and I'm sure i will be corrected as I have never owned or worked on an engine driven machine.