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I bought a 95 240sx se as a project car with a blacktop sr swapped in it. I bought it knowing it didn't run. It cranks but no fuel pump prime. So I replaced the fuel pump and it started up. After driving it around for a few minutes it died. I realized that it had no fuel so I filled it up but there was no fuel pump prime again and now it barely wants to crank. All the fuses are good and most of the ground wires are good so now I am stuck. Any help would be greatly appreciated

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  • Welcome to Motor Vehicle Maintenance & Repair! It could just be you got a bad pump. It happens.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Apr 3, 2020 at 0:01

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The ECU controls the fuel pump by providing it a ground. If you have a wiring diagram you could find the pin on the ECU connector and see if it's ~0 volts to ground for a few seconds after turning the key to start. 'Most grounds are ok' sounds suspicious. Or maybe find the fuel pump connector (under back seat?)and GUESS which one is the ground pin and jumper it to see if pump runs

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  • I have the ecu pinout diagram floating somewhere in my computer so I'll dig that up and give it a try. The fuel pump is in the trunk and I have it all pulled out, I tried supplying 12v to it and it didn't run
    – Robbie
    Commented Apr 3, 2020 at 1:41
  • @Robbie if the ecu makes the pump run by switching the ground then you supplying 12v won’t work unless you supply a ground as well.
    – Solar Mike
    Commented Apr 3, 2020 at 5:27
  • When you changed the pump did you look into the tank and see what condition it was in. It may be full of sludge. Also consider changing the filter when you replace the pump.
    – mikes
    Commented Apr 3, 2020 at 10:19
  • Update: So I was grubbing around the internet all last night looking for an answer and I saw something that sad jump pins 3 and 5 on the fuel pump relay. So I did and the fuel pump kicked in, I had a brand new fuel pump relay so i plugged it in but it didn't work. What does this mean is my ecu bad?
    – Robbie
    Commented Apr 3, 2020 at 14:28
  • Yes ,ECU controls relay , check loom (power/GND) from ecu harness to relay coil, otherwise replace ECU
    – binaryOps20
    Commented Dec 30, 2020 at 5:19

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