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3 wire oil pressure unit? wth!

Discussion in 'The Hokey Ass Message Board' started by shtterbug8, May 6, 2012.

  1. shtterbug8
    Joined: Jul 31, 2011
    Posts: 512

    shtterbug8
    Member

    i ant never seen this before. working on my 51 chevy earlier trying to hook up some gauges. well the engine 350 chevy has a oem 3 wire oil sending unit. i ant never seen such a thing. ive only seen 1 wire units before. just for giggles i wanted to hook it up and see if it works. i dont know where to hook the three wires up to. any idea? one wire would go to the guage, im guessing one must be a ground. is the other B+? or am i wrong all together?

    the unit im talking about is behind the distributor.:confused::confused::confused:
     
  2. chevy59409
    Joined: May 7, 2011
    Posts: 77

    chevy59409
    Member

    1 wire for the gauge .the other are for the fuel pump.but i dont remember which ones with out looking at a wire schematic
    chevy59409
     
  3. firstgear
    Joined: Jun 11, 2011
    Posts: 112

    firstgear
    Member

    Found this with a Google search....

    "the fuel pump relay must be energized through the oil pressure switch. (No oil pressure = No fuel pump.) "


    Found this on another forum... http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=774586


    "I will need to hook up all 3 wire becouse tan is for gauge and the other 2 are for fuel pump relay fail safe the car will still run.What I need to know is where the wire are on the plug.The wires are in a triangle shape one at the top and 2 at the bottom,the harness that I have I got from Summit and the wire are black so I need to know what wire go where."

    Hopefully the post and link above will help.....
     
  4. 26 roadster
    Joined: Apr 21, 2008
    Posts: 2,019

    26 roadster
    Member

    the oem sender works on the oem gauge correctly anything else is ???
     

  5. Bumping an old thread for more info.

    I need one of these 3 wire oil pressure switches for the gauge and fuel pump.. Its going into a SBC.

    Anyone have a part # or an application where they were used so I can tell the parts guy ....

    "I need a oil pressure switch for a ------ "

    Thanks for that one ! !

    Now a big thanks for a digram of the terminals.
     
  6. Just put a one wire sender inthe hole that is the proper OHM value for your gauge, then hot wire the relay or by pass the relay all together and wire your fuel pump to come on with the key or a toggle switch. Keep it simple. If you are using a stock oil pressure gauge or light that sender isn't going to work anyway.

    Wait a minute doesn't your '51 have a mechanical gauge?
     
  7. There is also a two wire oil pressure switch, when it sees pressure it will complete a circuit.
    You can use that for a relay trigger or for an electric choke or any other thing you want.

    I had mine set up to use that , however I buggered up the plug above the oil filter and now I need a 3 wire because I only have one hole now.
    Fuck me running !!
     
  8. mike in tucson
    Joined: Aug 11, 2005
    Posts: 520

    mike in tucson
    Member
    from Tucson

    I used the three connection unit on my rock crawler to kill the fuel pumps if the engine dies. I asked for an oil sender for a 96-99 Vortec 350 pickup truck. The mating connector came from Auveeco (spelling?)
    mike in tucson
     
    Last edited: Oct 10, 2012
  9. I *think* the oil pressure/fuel pump sending units were first used on original Chevy Vegas
     
  10. DoubleJ52
    Joined: Jul 15, 2007
    Posts: 237

    DoubleJ52
    Member
    from Belton, MO

    The Vega sender opens with low oil pressure, the three wire units are a backup if you have a relay failure. Try to find one for about an 86-7 Camaro TPI I think will be what you're looking for.
     
  11. PonchoJohn
    Joined: May 1, 2009
    Posts: 238

    PonchoJohn
    Member
    from Fresno, Ca

    I had a three wire sending unit on an S-10 Blazer. It had a dummy light and a gauge driven off the same sender.
     
  12. HamD
    Joined: Mar 3, 2011
    Posts: 298

    HamD
    Member

    Hmmph. In my experience, those years Camaro had a single wire sender and a 2-wire switch which was used for choke or fuel pump. No different than the 4bbl applications of that decade & slightly earlier.

    An early 90s Camaro used a 4-wire sender/switch combo. Early 90s S10 did too.

    yeah!
     
  13. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 768

    MAD MIKE
    Member
    from 94577

    I was under the impression that the Buick 231(not the later 3800 variant) used this kind of oil pressure switch. Due to the Buick style oil pump housing wearing out when the clearances became too big there would not be enough oil pressure, thus rather than destroy the engine, the ignition would not have power.
    [​IMG]

    I'll try and dig up a schematic showing this feature.
     

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