I have a 1987 Land Cruiser. The battery holds a charge of 12.6 volts after charge, but after I drive it a little bit the starting is not so good. The battery has lost some voltage. The battery has been tested and the Alternator was tested. Each out of the vehicle. Both okay. When check the charging volts with engine running, I only get 12.4-12.6 volts. And the battery is slowly dropping as the engine runs. I have check the fuses for parasitic drop and the fuses check out okay. But the Ground to Neg side of battery shows a drop of at least 1-2 volts. I touched the alternator to get the drop. Visually, I can't see a problem with grounds, but it seems like I have a ground problem somewhere. Would you have any suggestions?