[jmeckel]

It also could be you have a poor ground. Start with cleaning the ground connections, also use a jumper cable and run it from the battery ground to the starter bolts or any place on the engine you can get to that you can get a good solid clamp on. If this fixes the issue than you need to go through all the frame to engine to body ground points and clean them up, including engine pans. Another option is to run a #2 or larger soft copper cable from the engine (I attached to one of the starter to engine mounting bolts) to the battery ground cable to frame bolt. Again make sure there is no rust, paint, dirt..... etc. at the connection points and that they are tight.