isx 450 hard start

[Kiko]

Hello all. New to this forum. I am having trouble with an Isx 450 in a Volvo truck. When cold the truck is a few hard start. It cranks and cranks with no smoke. Once it’s running it runs great with lots of power. When running the fuel pressure on insite is about 250 at idle. Now I was thinking it’s a fuel prime problem. This engine did not come with a lift pump but has a Cummins lift pump that was added. When priming the fuel pressure is at 4 to 5 psi. Insite says it should be 10 +. When I take any of the lines off it has all kinds of flow and doesn’t seem to have any air in the fuel. I tried pressurizing the tank and could get prime pressure up to 12 psi. I thought this helped but when left overnight it was still a hard start with the same process. When monitoring the fuel pressure when cranking it slowly builds up to about 80 psi and then fires. Cummins wants 13000 for a new primer pump which is ridiculous. I did a cylinder cut out test and all cylinders are firing. Plus did a contribution test and all cylinders appear to pass. Now how long should the heat pump crank to build up pressure for firing when starting. Or could this engine need to see proper oil pressure to fire etc. kind of stuck on this one and could use some help.