This is a 97 12V in a 2500. When it is cold, I wait to start, crank it over and it fires right up. When it is warm I need to give it throttle to start. When it is really warm I need to floor it. Otherwise it fires and dies.

Does anyone know what this could be? Fuel pump? Thanks in advance.

Sounds like it is losing prime, have you recently changed your fuel filter? If so you may have damaged the o ring and it is now leaking.
Pumps on 12v are not very common, how many miles on it?

haha shit shows what I know about my diesel. I havn't changed the fuel filter. Miles are up to 258,000. I might throw a new filter in there now that you mention it, but wouldnt a clogged filter affect normal operations?

Usually, if the filter was clogged it would just run worse and worse, and starting would be the same each time. I would throw a new filter on it since you dont know when it was last changed. At the same time I would look over all the rubber lines on the fuel system. Some of them are notorious for leaking, but only air, and not fuel. This would allow air to enter the system causing your problems. I highly doubt its the lift pump, they are fairly robust units. How long do you have to crank it for to get it started when it is "really hot"?

When you give it throttle to start, it fires right up. Less than a second of cranking.

Damn! On a diesel changing the fuel filter every 10-15k miles is crucial! Try the filter, if it still does it then you probably have an air leak somewhere.