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No Power to Fuel Pump After Engine Swap

Discussion in '1st Gen. Tacomas (1995-2004)' started by Nate0303, Feb 6, 2025.

  1. Feb 6, 2025 at 8:09 PM
    #1
    Nate0303

    Nate0303 [OP] Well-Known Member

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    So my truck is a 2003 3.4L MT and I just swapped in an engine from a 2001 3.4L MT with the 2001 ECM and it cranks but won't start. I have gone through the below steps to narrow it down to no voltage supply to the fuel pump but I don't know where to go from here.

    First thing I did was swap the crank sensor, plugs and coils from my old engine which I know were good. Then I sprayed the MAF sensor with some MAF cleaner. Still cranks but won't start.

    Second thing I did was check the EFI fuse and that was good. I then popped the intake off the throttle body and sprayed some fuel in there, reconnected everything and when I cranked the engine it tried to start. I then disconnect the fuel supply line in the engine bay and got nothing coming out when it was cranking.

    Third thing I did was take the wiring connector off the fuel pump and supplied voltage directly to the fuel pump and it works. I then put a voltmeter on the wiring connector and got 0 volts when cranking. I also swapped the fuel circuit opening relay just to be sure but still nothing.
     
  2. Feb 6, 2025 at 9:01 PM
    #2
    TnShooter

    TnShooter The TacomaWorld Stray

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    The fuel pump will not be commanded on until it sees an RPM signal.
    It would be super helpful if you had a scan tool to monitor data while cranking.

    But you can also see if the tachometer moves while cranking?
    Does the tach move when cranking?

    When need to start somewhere. Start there.

    I also understand you swapped the crank sensor. But that doesn't mean much.
    We need some more data.
     
  3. Feb 6, 2025 at 9:06 PM
    #3
    TnShooter

    TnShooter The TacomaWorld Stray

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    You can also check the 7.5A Ignition fuse too.
    It cost nothing to check, and it plays a role in powering the fuel pump.
     
  4. Feb 6, 2025 at 9:25 PM
    #4
    Nate0303

    Nate0303 [OP] Well-Known Member

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    I do have an ultragauge but it will not connector after swapping in the 2001 ECM. I don't get any rpm reading on the dash while cranking but when I sprayed some fuel into the throttle body and it fired for a second I did get rpm.
     
  5. Feb 6, 2025 at 9:28 PM
    #5
    TnShooter

    TnShooter The TacomaWorld Stray

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    Interesting....

    I think I seen that the DLC connector (OBD plug) had a power feed from on on the relays associated with the EFI or Fuel pump Relay.

    Let me check.....
     
  6. Feb 6, 2025 at 9:33 PM
    #6
    TnShooter

    TnShooter The TacomaWorld Stray

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    Do you have a voltage meter or test light?
    You are going to need on to further test things.
     
  7. Feb 6, 2025 at 9:35 PM
    #7
    TnShooter

    TnShooter The TacomaWorld Stray

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    We need to make sure the crank sensor is plugged in, and has a good connection to the ECM.
    Until we get a crank signal, we are at a stand still.
     
  8. Feb 6, 2025 at 9:42 PM
    #8
    TnShooter

    TnShooter The TacomaWorld Stray

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  9. Feb 7, 2025 at 6:54 AM
    #9
    Glamisman

    Glamisman Well-Known Member

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    Does the Check Engine light illuminate when you turn the key to the ON position?
     
  10. Feb 7, 2025 at 9:03 AM
    #10
    Nate0303

    Nate0303 [OP] Well-Known Member

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    I don't remember but I'll check tonight.
     
  11. Feb 10, 2025 at 6:50 PM
    #11
    Nate0303

    Nate0303 [OP] Well-Known Member

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    I got busy and am now back to messing with the truck. Check Engine light is not on and I checked power at the EFI relay and I am getting 12V.
     
  12. Feb 10, 2025 at 7:35 PM
    #12
    Nate0303

    Nate0303 [OP] Well-Known Member

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    Both crank sensors i have tested at 1.9k ohms which i believe is in spec. The wiring connector at the sensor looked good. No obvious damage to the pins.
     
  13. Feb 10, 2025 at 9:26 PM
    #13
    TnShooter

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    If the CEL is not on in the ON position, than the ECM is offline.
    We need to check powers and ground to the ECM.
     
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  14. Feb 11, 2025 at 7:25 AM
    #14
    Glamisman

    Glamisman Well-Known Member

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    The most common failure point is/are the ECU grounds near the DIAGNOSE plug on the upper intake driverside. You should see a group of wires to an eyelet.
     
  15. Feb 11, 2025 at 8:08 PM
    #15
    Nate0303

    Nate0303 [OP] Well-Known Member

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    3in lift on 285/75r16 toyo MTS, cbi Moab front bumper, headache rack, nfab Nerf bars, LED lights, double din head unit, kicker hideaway dub
    So if I swap in my original 2003 ECM and the CEL is on with the key in the ON position, then the 2001 ECM that came with the engine is bad? Or is there a way to bench test the ECM to confirm?
     
  16. Feb 11, 2025 at 9:02 PM
    #16
    TnShooter

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    It's worth a try.
    But I'd want to make sure the pinout is the same for both.
    Just because I'm "that way".

    I'd hate to dead short an ECM. But, generally, that doesn't happen.

    Anyways, to answer the question.
    Yes, you can do that. I the CEL comes on. The ECM is online.
    And your scan tool should connect.

    All that said, I'm still leaning towards a power/ground issue.
    But swapping the ECM is not a "bad" idea. Try it an see....
     
  17. Feb 12, 2025 at 6:41 PM
    #17
    Nate0303

    Nate0303 [OP] Well-Known Member

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    3in lift on 285/75r16 toyo MTS, cbi Moab front bumper, headache rack, nfab Nerf bars, LED lights, double din head unit, kicker hideaway dub
    Well I put in the "old" 2003 ECM and the CEL comes on and I get voltage to the fuel pump when cranking. Is my best option swapping over the 2003 throttle body and wiring harness onto the "new" 2001 engine?
     
  18. Feb 12, 2025 at 8:14 PM
    #18
    TnShooter

    TnShooter The TacomaWorld Stray

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    Yeah. You need to use the original harness.
     
  19. Feb 15, 2025 at 1:30 PM
    #19
    Nate0303

    Nate0303 [OP] Well-Known Member

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    3in lift on 285/75r16 toyo MTS, cbi Moab front bumper, headache rack, nfab Nerf bars, LED lights, double din head unit, kicker hideaway dub
    With just my luck swapping the engine harness, intake manifold and throttle body worked. BUT something went wrong with the clutch while installing the engine and it is acting like the clutch is engaged all the time. So the truck now runs but it won't move.
     
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  20. Feb 15, 2025 at 2:41 PM
    #20
    Glamisman

    Glamisman Well-Known Member

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    Can you shift between gears with the motor off? Does the clutch "feel" normal as far as throw goes?
     

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