I've had 2 weird no-start issues with a couple of Taurus I've owned. One had a battery terminal(factory)that had a hairline crack in it, caused the issue you're having,, totally random no power at all, then it would work.. I looked at the terminals, even loosened and retightened them, felt good, but actually wasn't, found it because the terminal finally broke open a bit.. second issue was the little black box that sits on your radiator, can't remember what it was called on the 87's, maybe integrated controller????, I think it's now called the ccrm, holds a bunch of relays I think,, anyway it had two ground wires coming out of it that were joined in a connector to the radiator support on top, one of them came loose in the connector, no power anywhere.. I found that one by accident, my wife calls says my car won't start, I showed up, started tugging on various wires checking them out and poof, car fired up.. can't say any of these apply in your situation, just a couple of oddities that happened to me, I think both would have been a pain for someone to diagnose