I have a 1997 Dodge 2500 Van with a 5.2 engine. It won't start. It wants to but just won't stay running. I have replace computer, fuel pump, timing chain and gears distributor cap, roter button, pickup coil, coil, spark plugs. And fuel injectors. Still won't start. One advise was that the new plugs have like a black sut on them. And I was told that the fuel is being injected to late. How can this be corrected?