I am looking to buy a 1987 528E. There is an issue with the fuel. First, the pump has no power whether in the car or jumped. Second, how much pressure should there be for the fuel? Third, is there an after market pump I can get to replace the one that is in it? There power to everything else in the car, it tries to start. I am wanting to know if it is fixable and a ruff guess at how much it would cost. Thanks