I have a 04 Ram 1500 with a 5.7 Hemi. It has me stomped as to what is going on with it. After changing out the spark plugs it would not start and I figured out that the fuel pump needed to be replaced. After replacing it the truck fired up and ran better than ever. The next time I went to start it all I got was cranks until it eventually started but stalled out just a few minutes later. I can manage to get it to idle for about 5 minutes before it cuts off. It is not ahowing any codes.

 

Does it stumble and die, or is it like someone just switched off the key?

 

more like it’s been turned off. It stumbles for maybe a second if it’s idling. When driving it just turns off.

 

I would be tempted to put a fuel pressure gauge on it, and let it sit and idle till it dies.... See what fuel pressure is doing right BEFORE it dies.