Engine troubles

After a long driving trip, the van just stalled. The engine would still try to turn over but it seemed like it was not getting any fuel. Changed out the fuel pump, fuel filter and the fuse. Ran smooth for a bit, then it would not charge. Found out it was a default alternator. Changed out the alternator, Pigtail to that alt. And changed the battery. Now it acts like it wants to start, but it will not actually turn over and start. It is doing almost the same thing when it lost fuel and I had to change the fuel system. After about two to four attempts to start it will run! Can take it anywhere. There is a small oil leak coming from the valve covers. Also noticed little bubbles coming out of the head I think, just below the valve cover. Any kind of information would be great. I plan to change the valve cover gaskets here soon.