Just went through this today and did find my starter was bad. While all of this was in the Haynes manuel, this guys write up on how to test the starting system was more helpful. http://easyautodiagnostics.com/bad_starter_test/starter_oncar_tests_1.php Probably the hardest part of performing these tests on my '98 Suburban was trying to get at the appropriate terminals on the starter. I found the easiest way to access them was to remove the "splash shield" from the passenger wheel well. The starter is right there, just inside of the frame rail. (A flashlight was almost essential to see things well). It's a little tricky to not short the battery wire against the heat shield, but, with a little care, I was able to probe each terminal and determine that all the voltages were good, and that the battery cables were not corroded. Now it has a new starter and starts strong again.