My 98 12 valve Cummins is losing prime when I shut it off. Also, when I do get it re primed and running, it would run fine but there would be spurts of it bogging down and blowing white smoke. I have to hold it at a high rpm in order to keep it running. The problem first started with it acting like the engine was really cold when I went to start it so I changed the filter and started having this problem. I have a feeling that it could possibly be the fuel pump, but I'm not sure.

 

I bet air is leaking into the fuel system somewhere between the fuel filter you just changed and the fuel tank.

Loose hose clamps, old rubber or rust metal lines, not sealed fuel filter housings / lines and banjo bolts without sealing washers come to mind.

 

I did some more looking around today and found out that where the rubber line attaches to the metal line, there is supposed to be hose clamps. But, on my truck there was none so I picked up new rubber hose and some hose clamps to put on for now.

 

Sometimes it can be that simple.
Hoping that fixes your problem.

 

Me too. But if the rubber hose between fuel filter and injection pump is the original, change it now. They don't last this long. Geno's has a good one.

 

I found out the problem. The sending unit in the tank broke free. It broke where the 4 tabs screw into the cap so the entire unit was floating around in the tank. The sheet metal ended up wearing a hole into the feed line inside of the tank.

 

I don't think I've heard of that one before. Glad you found it and posted your find, so it may help someone else!