Joe,

If it runs good sometime, the pump probably doesn't have to be replaced.

Make sure fuel with some pressure is getting to the IP. It could just be air locked from a air leak in the fuel line. If it seems to be getting enough fuel read on.

I'm with Jetboy. Take the IP off and take it to a Bosch or Diesel injection shop.

If there is something simple wrong with your IP, they can fix it a reasonable cost, much less than the cost of a rebuilt IP.

P E H