John-
You probably already have this covered...but just in case...make sure
you don't have any Teflon tape or pipe thread sealant on you single
wire sensors. They are grounded through the housing and Teflon tape
and thread sealant insulate them from the engine ground.

Joe Hull
Bellevue (Seattle), Washington
Cozy MkIV #991 (working on Engine & Electrical & Finishing)
http://www.maddyhome.com/canardpages/pages/JoeHull/index.html