I just bought a 93 f250 7.3l idi and it first smokes black smoke then a burst of white smoke..I did have to add anti freeze..Any Ideas??and when it first cranks up it cranks right up then dies unless i give it fuel.It does have an aftermarket exhaust on it.Any ideas on that problem?One injector return line seal is also leaking..Thanks ahead of time.

 

Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - Ford Truck Enthusiasts Forums Here is a link to the page for your engine, maybe post your problem there.
However you need to fix the return line leak. Maybe get a return line kit and replace it all. Any leak will allow air intrusion and so fuel drain back, which shows up as engine wanting to stall shortly after starting.