Oil pressure gauge wire

Discussion in 'Gauge, Speedo & Instrumentation' started by Ensign10, Sep 14, 2018 at 1:32 AM.

  1. Ensign10

    Ensign10 Junior Member

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    I have a 1986 K30 crew cab, factory 454 truck, now has a Cummins. All of the gauges currently work except the oil pressure. The PO plumbed in a mechanical oil pressure gauge, and that tiny capillary line leaks at the ferrule. I tried to just straighten it out but it still leaks a little bit. I'd rather just have the gauge work anyway. The engine bay still appears to have all of the factory wiring. Can anybody tell me which engine bay wire (color/trace) goes to the oil pressure sender?
    Much thanks

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  2. Charlie

    Charlie Full Access Member

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  3. bucket

    bucket Super Moderator Staff Member

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    Iirc, it's a single tan wire. Usually with a rubber connector at the end, with a female spade inside of it.
     
  4. Ensign10

    Ensign10 Junior Member

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    I was suspicious about a tan wire running through the firewall bulkhead connector that is labeled "electric choke" in the engine bay. I'm not really a carb guy, but I didn't think there was anything in the cab that would run to an electric choke...

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  5. Ensign10

    Ensign10 Junior Member

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    Thank you for your response.

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  6. Ensign10

    Ensign10 Junior Member

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    So the plot thickens.
    I took the cluster out to chase the oil pressure wire because nothing was working. I found the little tan wire in the engine bay and at the cluster plug.
    It doesn't read grounded, and all three black grounds at the cluster read as such, and the 3 red wires read 12v.

    The oil gauge has the needle pegged way past max pressure when the key is on. When I unplug the cluster, the needle will drift up. But pin back over when the cluster is plugged in and the key turned on.

    Any thoughts?
    Thank you in advance

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  7. Jerry phillion

    Jerry phillion Full Access Member

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    Jacob, if I remember right, to check if gage is ok, turn key on,
    Have someone watch gage while you crawl under truck. Take tan
    Wire and touch to engine for ground. If gage is good, needle
    Should go left to "O".
     
  8. bucket

    bucket Super Moderator Staff Member

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    Right, ground out the tan wire to the cluster and the gauge should go all the way to the low side.
     
  9. Ensign10

    Ensign10 Junior Member

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    Great, thank you for the replies. The gauge apparently functions exactly the opposite of what I had assumed. I'll try grounding out the the tan wire tomorrow.
    Thanks again.

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