Have a 1987 300TD and can't find a spec that calls out the lift pump pressure for the 603...found several references regarding output pressure for the 617's which appears to be around 15 - 19 psi. One thread discussing spring modifications mentioned 603 output at 30 psi but I wasn't sure if that was after tweaking the spring. At 3000 rpm my pump will push-out around 13-14 psi and if I briefly pinch off the outlet it will go up another 1-2 psi. I've replaced all the 'O' rings in the lift pump and figured before I order a new spring from Germany or a new pump I need to nail down just how far away I am from what the pressure should be. Any help, greatly appreciated.