Post the year, make and model of the vehicle (in new question) and one of us can tell you if it is negative or positive ground.
cracked heads or a blown head gasket can be the main source
Where is the computer located in the 1995 ford e250 4.9l engine
where is the crank sensor located on a ford e250 1999
where do you find horn fuse on 1993 e250 ford van
Yes.
No it is negative ground.
ford van 2013 E250 inide lights wont work
WHERE is the blower motor fuse on a 1999 ford e250 4.2 L
Where is the fuse for running lights on 2001 e250
Try https://web.msslib.dealerconnection.com/RightSite/getcontent/myfile.pdf?DMW_OBJECTID=09000c588020338a (page 125)
The vehicle speed sensor on Ford E250 is located underneath the vehicle on the transmission beneath the intake mainfold.