My son is working on his van. 1991 Chevy Astro Van, 4. 3 liter. It would only start intermittently. If you crankred on it for a while then left it alone for about half an hour then try it again, it would start. Now it will not start at all. He took the fuel line off upstream of the fuel filter (which he changed out) and there is no fuel. He swapped the AC relay and the fuel relay and still no fuel. Before he buys the fuel pump, is there anything else he can check? Thanks, everyone. Larry