[Dangerous Doug]

I've run into a similar problem several times. Thought it was the fuel pump cutting out, but it wasn't the fuel pump.

I think your coil is failing. Here's why: If you run for about 40 minutes, your engine gets nice and toasty. So does the coil. As the coil heats up, the windings on the inside heat up and expand, and when it expands (and presumably the material in the coil is breaking down) it shorts out. When the car cools down, the coil cools and the wires no longer short. Ta-da! It starts up and you drive home.

Grab your trusty multimeter and head out for a drive. Don't worry, it will start again, but go somewhere you can get off the road easily. Oh, before you go, test the +/- sides of the coil with your multimeter (DMM). Make sure you have it on Vdc NOT Ohms (common mistake). Head out your for your drive. When it dies, pull over, pop the hood with the ignitiion switch "on" and test the +/- poles on your coils. I'd be willing to bet you'll find that +/- now read the same.

I've figured this out on a '70 Camaro, a Fiat Spider, and a Volvo (my wife's car, which spent several days at a Volvo shop with multiple mechanics scratching their balls..., uh, I mean, heads.

If this works you owe me a beer and/or a shot of Patron tequila.