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2G Test fuel pump/mfi relay

Posted by JGeezyyy, Jan 12, 2019 at 1:16 PM

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  1. JGeezyyy

    JGeezyyy Proven Member

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    Diagnosing a no-start. Fuel pump isn’t turning on. Tested the fuel pump by directly connecting power to it and it turned on. Trying to test the relays. In the picture below it’s sayingto test the continuity between 2-4. Do i have them labeled correctly in the pictures? And this is just with the multimeter correct? I’m not good with this kind of stuff. I connected the black end of the meter to “3” and the red to “4” as I have in the pics. On the left terminal it’s only showing 1.xx. The terminal on the right isn’t showing anything for a reading. I know it’s supposed to be 70 if done correctly but I just want to make sure I’m testing it correctly so I can rule it out.
     

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  2. steve

    steve DSM Wiseman

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    The manual usually shows pin numbering looking from the top (where the wires go in) of a connector. So I think you have them labeled incorrectly. You are measuring the relay and not the harness, correct?
     
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  3. pauleyman

    pauleyman DSM Wiseman

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    Very easy to just jump the test connector on the firewall. Might help rule out relay
     
    1997 Eagle Talon TSi AWD

    Street Build

    T25   manual
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  4. JGeezyyy

    JGeezyyy Proven Member

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    Sorry for the labeling I should have labeled the relay.

    At first I’ll admit I was testing the harness. But I’ve been testing the relays out of the car for the past day or 2 and can’t get the multimeter to give a solid reading. It’ll flash a random number, sometimes 30, sometimes 90, then drop back down to 0.

    I’ve been testing them per the manual in the picture. Am i testing it wrong?

    On 2gs is it the black or blue connector? I’ve been getting mixed answers. When I tried this last week nothing happened on either connector so again I wasn’t sure if I was properly testing.
     
    Last edited by a moderator: Jan 14, 2019 at 2:49 PM
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  5. steve

    steve DSM Wiseman

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    There are two parts to the relay, the coil and the contacts.

    The coil will have a fixed resistance between it's two connectors (pins 2 and 4).

    It's the coil that gets battery voltage fed to it which creates an electromagnet that cause the contacts to connect. When there is no voltage across the coil, the contacts are not connected (Infinite ohms between pins 1 and 3) and when there is voltage across the coil, the the contacts are connected (0 ohms between pins 1 and 3)

    Looking down into the relay with the ridge that the connectors snaps on facing away from you the pins are:

    1 2
    3 4

    On the 2g's that use these two relays rather than the old MPI relay both relays are the same, one's for the car MPI circuit and the other for the fuel pump.
     
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  6. JGeezyyy

    JGeezyyy Proven Member

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    Okay so I think I’ve been testing correctly then. The way I have it in the picture is the correct orientation if I’m not mistaken?
     

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  7. steve

    steve DSM Wiseman

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    Your holding them the way I'd expect. The right top and bottom pins should measure about 70 ohms between them. What do yours measure?
     
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  8. JGeezyyy

    JGeezyyy Proven Member

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    I have the red on pin 4 (bottom right) and the black on pin 3 (top right). When I try to test the ohms on one and 3 it’s always a different number, sometimes 30, sometimes 90. But it always goes back to 0 if I keep the test leads on.
     

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  9. JGeezyyy

    JGeezyyy Proven Member

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    So I just noticed. I’ve been testing 1 and 3 instead of on 2 and 4 while testing. They are both around 71 and 72 ohms.
     
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  10. JGeezyyy

    JGeezyyy Proven Member

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    My only question now would be where would I test now? If the fuel pump turns on outside of the car and the relays are good?
     
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  11. steve

    steve DSM Wiseman

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    St. Charles, Illinois
    The next test as shown in the FSM is to apply battery voltage to 2 and 4 and see if 1 and 3 switch.

    I don't have access in the mountains to my FSM so I can't say what color wire the Fuel Check Connector under the hood is. But to use it you apply +12v to it and the pump should run.

    However that test bypasses the ECU and fuel pump relay operation, it's just feeding 12v to the same place after the FP relay.

    Without DSMLink it's difficult to get the ECU to force the fuel pump on. You can check to see if by grounding the FP relay pin at the ECU that the relay activates and runs the pump which leaves the ECU as the last unknown.
     
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  12. JGeezyyy

    JGeezyyy Proven Member

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    Naugatuck, Connecticut
    When 2 and 4 are getting power, do I test ohms on 1 and 3? If so, it flashes random numbers but eventually go down to 0. I have dsmlink, but I can’t get my cable to connect anymore. Also, when I tried the check connector last week, nothing happened. So it’s confusing me :banghead:. My check engine light did come on with the key turned to on as it’s supposed to, then turned off. So no clue why the cables not working. I even sent it in to ECMlink and they said the cable was fine. Just received it back the other day actually. I have a video of the car trying to start last week but can’t seem to figure out how to upload it. (Stupid iPhones LOL)
     
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