I rebuilt the fuel transfer pump on my Cat D6c 10k dozer, when reinstalled pump to test with engine running a small dribble of fuel still exit the drain pipe. Fuel pressure with original pump was always in green on gauge. I replaced pump with aftermarket pump. Engine runs fine with no fuel leak but fuel pressure is in red at idle and at high idle it is at the beginning edge of green on the pressure gauge. Will a stiffer spring on regulator valve bring up fuel pressure in the aftermarket pump?
Keith-50, I would first connect a good, trustworthy & accurate pressure gauge and get some real numbers to work with. Who knows what your 40-year old instrument panel gauge is really telling you. Good work on getting that old girl to stop leaking. Sometimes those old transfer pumps don’t take a new seal if the shaft gets too worn.