I have a 2000 ford lightning that will not stay running. We thought that we had a fuel pump issue, but we have changed both pumps and put in a new fuel filter and relays. It will start up and run for about 10 seconds. If you give it any gas at all it will die. Some times it will if you hit the gas but will run just for a little bit. It is losing fuel pressure on our gauge. Any one have a situation like this one and how can we fix it?