1994 Ford E-Series Van eng dies or won't start

This is actualy a open air trolley but they used a 1994 ford 460 ci fuel injected engine with an allison trans
about a month ago the vehicle started not starting after it had been started a few times let it sit and it would start. Now it has gotten to where it starts and runs for a while then dies let it sit and it will restart it is like someone turned the key off. Yesterday I started it cold and let it idle 20 min later it died and started right back up ran 10 mins and died then restarted 10 mins later died again no restart checked there was no spark the coil is brand new the tif moduale is new. I had 12 volts to the + side of coil and 12 volts to one of the distributor connector terminals. But no spark I put everything back together let sit over night and it started thi morning
dist was replaced 15 months ago with rebuilt.(Sometimes wont start hot or cold)