My 98 Expedition wont stay started?

You should have drained the fuel as your first step.

Is it runnin like shit? Is the CEL (check engine light/service engine soon) lit up? If it’s got a check engine light on, you need to have it properly diagnosed. Please don’t just take it to Autozone for them to “diagnose” it.. there’s a big difference between reading the codes, and diagnosing the cause of them. If it won’t idle on its own then there’s a multitude of possibilities, more than likely though a competent technician will know where to start given the codes are present. Until then ma’am you’ll just be wasting your time, and money throwing parts at it hoping one of them fixes it. Best O’luck to ye.