HELP! Fuel pump issues

  • #1

    HELP! Fuel pump issues

    Hey guys, was driving my car earlier and it just randomly shut off while driving for about 15 min (right after I just finished detailing it, of course). Pulled off into a parking lot to diagnose. Found the fuel pump wasn't priming. Replaced relay b/c it terminals were gross and needed to be replaced regardless of the issue. Anyways, the fuel pump wasn't turning on at all..no priming or anything. There are 12v going to the pump, and the pump will only turn on if I ground it to an external source ( if I understand correctly the pump circuit is ground switched, correct? and it has two ground circuits for the pump).
    So I was wondering if someone could point me in the right direction as to where to find the ground issue i.e. which pin on the ECU it is, which ground circuit to check, etc. Sorry i'm just trying to get this fixed ASAP…don't like my car being in a random parking lot for very long!
    Thanks in advance

    '86 NA2T: Cone filter, 3 in. turbo back, poly engine mounts, stock t3, tokico 5-ways, rattle canned engine bay, etc etc

    "As I lay rubber down the street, I pray for traction I may keep, and if I do begin to slide, please dear God protect my ride! - Amen!!!!"
  • #2
    The signal is from the ECU itself.
    I have seen this issue when the ECU gets water inside or and when the ECU is going out.
  • #3
    Thanks for the quick reply! So is there any way to check if it's the ECU and not a problem in the actual wiring w/o having to buy another ECU first? Would there be any other symptoms or signs of an ECU going out?

    '86 NA2T: Cone filter, 3 in. turbo back, poly engine mounts, stock t3, tokico 5-ways, rattle canned engine bay, etc etc

    "As I lay rubber down the street, I pray for traction I may keep, and if I do begin to slide, please dear God protect my ride! - Amen!!!!"
  • #4
    There is probably nothing wrong with your wiring.
    It's likely the ECU.
    You can try to remove the ECU, open it up to see if there is any moisture, and try again.
    Otherwise, try a different ECU.

    It's never a bad idea to keep a few spare ECUs for your Z
  • #5
    Originally posted by amreboot View Post
    There is probably nothing wrong with your wiring.
    It's likely the ECU.
    You can try to remove the ECU, open it up to see if there is any moisture, and try again.
    Otherwise, try a different ECU.

    It's never a bad idea to keep a few spare ECUs for your Z
    Alright I will try and get my hands on one. Also, I forgot to mention that I have a walbro 255 pump installed..could this be an issue with stock fuel pump wiring or is it safe to run off the stock wiring? Thanks for the help

    '86 NA2T: Cone filter, 3 in. turbo back, poly engine mounts, stock t3, tokico 5-ways, rattle canned engine bay, etc etc

    "As I lay rubber down the street, I pray for traction I may keep, and if I do begin to slide, please dear God protect my ride! - Amen!!!!"
  • #6
    Well, the Walbro could have fried your wiring, but this is usually done back at the pump itself, or near the blue connector.
    So check around there for any melted wiring.

    Also, you may consider doing the dedicated fuel circuit.
    You can search for that. Good writes up.
  • #7
    Originally posted by amreboot
    Well, the Walbro could have fried your wiring, but this is usually done back at the pump itself, or near the blue connector.
    So check around there for any melted wiring.

    Also, you may consider doing the dedicated fuel circuit.
    You can search for that. Good writes up.
    Gotcha, well I went to look at the ECU and run codes (expecting code 22) and it won't do the self diagnosis test…which I've read means the ECU is no Bueno. Thanks for the help amreboot

    '86 NA2T: Cone filter, 3 in. turbo back, poly engine mounts, stock t3, tokico 5-ways, rattle canned engine bay, etc etc

    "As I lay rubber down the street, I pray for traction I may keep, and if I do begin to slide, please dear God protect my ride! - Amen!!!!"
  • #8
    A great upgrade is to take the connection that goes to the pump and tie it to the coil of a relay and let the relay switch the pump thus taking the amperage demand off the ECU. This isolates the computer from dealing with upgraded pumps, flaky old pumps etc.
    Cha iro

    enjoy building it yourself.
    if it fails, fuck it.
    at least you gave it a whirl.