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Thread: How To: Jump the RPM Relay

  1. #1
    Vin3299's Doc DeLorean03's Avatar
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    How To: Jump the RPM Relay

    The RPM relay is located in the electrical compartment behind the passenger's seat. It looks like this:

    rpm-relay-new-old-style-gre.jpg

    Once you've located it, unplug it from the electrical connector it's hooked up to. It'll only go back on one way specifically, so don't worry about how to reconnect when the time comes. From there, you need to devise a "jumper" - a wire with 2 male spade connectors - one on each end of the wire. Spade connectors typically are rectangular in shape. Once you've made the jumper, "jump the RPM relay" as seen in this picture:

    rpm-relay-jumper.jpg

    This, in essence, forces the fuel pump to run even if you are not trying to start the car. Once you've jumped the RPM relay as seen in the picture above, try to start your car. If it starts in this case, your RPM relay may be working intermittently. Unhook your jumper, re-hook the RPM back up to the electrical plug, and try to start your car normally. If it starts, good deal. If not, might need to look into a new RPM relay.
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  2. #2
    Not dead yet, also Admin. sean's Avatar
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    FYI, the wires in question that you are connecting with this jump:
    Brown
    and
    White/Purple.
    eBay selling at it's best I can tell you stock Delorians and quite a bit of slugs so the Turbo is a super nice up-grade.
    K-Jet: Causing electrical issues since November 5th 1955

  3. #3
    Owner since 2007 Farrar's Avatar
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    I would like to add that if the relay fails while you're on the road and you need a way to get your car safely elsewhere under its own power so that you can order a new relay, you can stick the other end of the jumper wire in the green wire's slot, instead of the brown wire's slot. The result is that the fuel pump will run when the key is on.

    The usual disclaimer about this being only a temporary solution applies. Also, I think it is a good idea to keep a fused jumper in the car for this, in case you have an electrical problem which caused the relay to blow.

    Farrar
    3.0L, automatic, carbureted

  4. #4
    Not dead yet, also Admin. sean's Avatar
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    Quote Originally Posted by Farrar View Post
    I would like to add that if the relay fails while you're on the road and you need a way to get your car safely elsewhere under its own power so that you can order a new relay, you can stick the other end of the jumper wire in the green wire's slot, instead of the brown wire's slot. The result is that the fuel pump will run when the key is on.

    The usual disclaimer about this being only a temporary solution applies. Also, I think it is a good idea to keep a fused jumper in the car for this, in case you have an electrical problem which caused the relay to blow.

    Farrar
    Great addition Farrar!
    eBay selling at it's best I can tell you stock Delorians and quite a bit of slugs so the Turbo is a super nice up-grade.
    K-Jet: Causing electrical issues since November 5th 1955

  5. #5
    Owner since 2007 Farrar's Avatar
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    Quote Originally Posted by sean View Post
    Great addition Farrar!
    Thanks; I had my second cup of coffee just before I wrote that.

    Farrar
    3.0L, automatic, carbureted

  6. #6
    Senior Member Bitsyncmaster's Avatar
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    The photo in the first post shows a green case green connector. That is the only RPM relay I can not accept as a core for my solid state relay. The pin footprint does not match my circuit board.

    An emergency jumper should have three pins. So you also power the Lambda circuit with the fuel pump.

    So you don't need to remember what colors or pin number.
    The pump wires are the two large gauge wires.
    Brown wire is always the power (battery +).
    The double wires in one pin is the Lambda.

    Running the pump on the green wire, I do not recommend to do. Our stock pumps run about 7 amps and some run 10 amps.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #7
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    Thank you for posting this! After hitting my head against a wall trying to figure out what was wrong, this got my DMC running in 5-min. Also let me know definitively that my relay was shot and I needed a new one. Vital information.

  8. #8
    Senior Member Chris 16409's Avatar
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    Quote Originally Posted by MacStainless View Post
    Thank you for posting this! After hitting my head against a wall trying to figure out what was wrong, this got my DMC running in 5-min. Also let me know definitively that my relay was shot and I needed a new one. Vital information.
    Contact Dave McKeen (Bitsyncmaster) to purchase one of his solid state RPM relays. It's a no brainier upgrade. You send him your old relay to modify.
    Chris Miles

    For Better or Worse I own a DeLorean!
    1983 Grey Manual, VIN #16409, Fresno, California

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