89 mustang fuel pump or fuel pump relay ??

Discussion in 'Fox 5.0 Mustang Tech' started by BonesBSO, Apr 15, 2008.

  1. I have a 89 Mustang was out driving around got home turned it off and now it won't start. I think it is the fuel pump because I can't hear it run when i turn the key on but i have read that the fuel pump relay can cause the same type of problem. Any other suggestions on what to check before I replace the fuel pump.

    Thanks any help would appreciated.
  2. Welcome to SN!

    Check fuel pressure. If it's good, note if you have spark and injector pulsing.
    Pull codes.
  3. Ok I checked the fuel pressure and there is none also checked for spark and it is good I will run some tests on the fp relay and the inertia switch when I get home tonight. how do i go about bypassing the FP relay with the ECC test conector.

    Thanks for your help
  4. For the $10 get the relay and install it.
    It is under the driver's seat.
  5. Update ok I replaced the FP relay now I can hear the FP relay click but still nothing from the fuel pump. any ideas.

  6. Grab your meter and test the FP relay terminals. Assume nothing. Test the relay coil by checking for accessory power and continuity to ground at the relay coil during the prime-out. Then check for constant 12 volts at the relay's common terminal. I have the feeling you might be missing this. If so, check the fusible link for the FP. It's located just off the starter solenoid (the pump gets power from the battery lug on the solenoid).

    To make testing easier, see Jrichker's post here. He shows a picture to jump the FP relay (via the self-test connector). This wire that gets jumped is a branch of the same one that is grounded at the relay.

    If while the relay is energized (and priming-out), you have 3 wires showing 12 volts, then go back to the pump and check the power and ground situation back there.

    Post up what you find and folks can take it from there.

    Good luck.
  7. Ok I will check that tonight when I get off work and do the test in Jrichker's post and let you know what I find.

    Thanks for your help
  8. Ok I did all of the tests in jrichkers post I have good spark at the coil,distributor and #1 plug 12v at the ignition switch and 12v at the FP relay wire and 12v on both sides of the inertia switch.

    I ran a wire from the EEC FPTP to ground and the fuel pump still won't run.

    Is it safe to say its time to replace the fuel pump I can't think of any other test to do and I can't even get to the wire on the pump without dropping the tank. is there any way to hot wire the pump just to see if it runs ??

  9. What did you find at the FP relay itself? You didnt even need to test at the interia switch if you had gone to the FP relay in the first place.

    I'd test the relay I/O's. Then go to the pump if you need to. I've been able to access the connector without dropping the tank (sometimes I have to lower it a little though). Depending upon what you find at the relay, this is the next place to go.

    Good luck.
  10. Ok I did do a couple of test on the FP relay

    1. Checked orange/Lt blue wire has 12v

    2. key on have continuity between red/black and tan/Lt blue wire

    3.key on PK/BK have a good ground

    I will go back and dubble check the FP relay tonight as for the pump connection I will have to wait until the weekend just not enought time or light after work.

    Thanks HISSIN50 for all your help
  11. Good. This is the load-side source for the pump.

    Ruh roh.
    I think you're talking about he tan/lt green wire. It should show continuity to ground when the FP is supposed to be active. Having continuity with a 12 volt source (red/blk) is not good.

    Pink/blk is not grounded. This should show 12 volts when the pump is running (this is the wire that really matters, as it delivers power to the pump).


    If you want to try and 'jump' the fuel pump, you can connect pink/blk to orange/lt blue (confirm the wire colors are the same in your car). This should be connecting the power feed from the solenoid to the to the normally open wire that leaves the relay and goes to the pump. If the pump works while doing this but not otherwise, the control side of the relay has an issue.

    For fuel pump schematics, check out the upper left side of this diagram.

    Diagram courtesy of S&2B's (site host) and Tom Moss (diagram author).
  12. Your right test 2. was the tan/lt green wire and i did have continuity to ground when the FP is supposed to be active. (clicking)
    On test 3. right again there was 12v at PK/BK but the pump did not run.

    I will try the jumper test when I get home tonight and let you know.

  13. Have you checked the inertia switch? It on the inside of the trunk behind the driver side taillight...its a red button that should be pressed down..Probably not the problem, but a possibility i guess
  14. If you have 12 volts at pink/blk, the relay should be working fine. Access the FP connector (it sits just above the tank and often has enough slack to pull it down and test without much fuss) and see if you have 12 volts across the terminals.
  15. Ok I wasn't able to get to the FP connector without lowering the tank so I droped it just far enought to get to the connector tested both sides and have12v so since i was this far i pumped out as much gas as I could and droped the tank it sounds like something it rolling around in the bottom of it. I'll clean the top real good and open it to see what it is but I'm out of time today so it will have wait untill tommarow.

    Thanks for all your help HISSIN50
  16. Sounds good. Since you know you have 12 volts of potential across the FP electrical connector, getting that pump out of there is the next logical step I see.

    It'll be interesting to hear what was in the bottom. :D
  17. Will the pump is out and it is dead as for what is rolling around in the tank it looks like a big pice of formed medal :jaw: I bet this means I have to replace the tank doesn't it.
  18. Is the piece of metal bigger than any opening in the tank? I'm with you - I wouldn't want to put that tank back up with that thing in there.
  19. Ya it is, I did a little checking and it is the fuel pump cup baffle it is suppose to be spot welded to the inside top of the tank. So I guess I will be replaceing the pump and the tank @#!*&#@! :( any suggestions on a good online parts store.
  20. Guys have been having ok luck with tanks coming from their local parts stores (they order them in but I don't think you pay shipping). They used to be just over 100 bucks new so with recent gas-inflation, they're probably 500 bucks.