Hey everybody, I have had this exact problem with 2 Toyota trucks. One being my 1989 SR5 4x4 and the other my 1990 Itasca. I had same issues as described. Turn key and nothing happens. Battery is fully charged. I would hit starter with bar several times and it would start (sometimes). I knew the starters would good because I had them rebuilt. After many hours searching the net I found the cure. When the key is turned to start vehicle it sends a milliamp of power to the selinoid .. After years of starts the ignition gets weak and the starter doesn't see the proper amps. So it will not start.
I bought a "hot shot" relay from Summet racing. Its is a easy install with all proper wiring. Basically my starter gets a full 12v to the selinoid now. This "hot shot" relay is built for race car so they can start when the engine and starter get real hot. Now it has been quite a wile since I have done this and can't recall the specifics so a online search will give you the answeres to your questions. This mod has worked great and have not had no more starter problems.
Hope this helps
Jay
