I just put in my 5th fuel pump(83 280ZX 2+2 167K miles) in 3 months. This one lasted 20 miles. All the pumps I put in run noisy and the whirring (or grinding as it were) sound fluctuates at idle. Sometimes after the car dies if it sits 1/2 hour or so it starts and will run for 1-3 mile then Blaaaaaaa. no go and finally the pump goes out. The pump runs very warm almost hot to the touch even at idle and makes a lot of noise. Today I pulled the tank sending unit cleaned the strainer blew out the lines replaced the tank to pump line replaced the pressure regulator (had a spare one on hand) the lines going to and from the reg. and all the clamps on the lines thinking there might be an air leak. I used clear fuel line to see if i could spot any bubbles and noticed some on the return to tank line from the Pres. Reg. One of the injectors has a small leak. I think that might be the source of the air in the return line but would that affect the supply side of the system? Could the EFI system be sending overvoltage to the pump? I'm running out of ideas.