问:起动电路问题,不会曲柄。2500年2000年的GMC萨瓦那

我的车有一个起动电路问题。灌装坦克在加油站的时候,我的车不开始。我不得不把它远离泵,然后它开始。当我回到家,关闭它,它不会重新启动。我有检查电池和负载测试失败和更换,但没有改变。然后我跟着PnP型开关的电路,但没有信号在公园;绕过来验证和更换开关。我发现了一个糟糕的起动继电器和取代它。仍然没有改变。然后,我检查了起动信号和我现在有信号但货车仍然不会曲柄。 I removed the starter. Except for worn brushes, the starter was fine but I went ahead and replaced it. It will now kick the starter, but still will not crank. I have checked all fuse block power and all is fine there. The battery has full power and it also passes a load test and a visual inspection of the wiring. There are no breaks and no corrosion. In the starting circuit, all components checked out okay. I tried a test jump at the starter to bypass any other possible problems, but the van still will not crank over. The starter engaging can be heard, but it will not crank. It did start twice, but not cranking over. I also inspected the ground from the battery to the the engine block and braided strap to frame. Except for some road dust, it seems dry and no sign of corrosion. Without my van I am losing income, so could you please tell me what you think I need to do next to fix my vehicle. Thanks.