Oil Pressure Safety Switch questions???

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  • southcoasting
    Senior Member
    • Nov 2011
    • 164

    Oil Pressure Safety Switch questions???

    OK,
    So, have been browsing trying to learn more on things I see on my engine while going through it and looking at it...

    I have not started it yet as I bought my boat in August and its been winterized since...

    One thing I was looking at is around the oil pressure switch, there is a lot of oil accumulation...I think it's leaking so was thinking of just replacing it and getting the Moyer marine version that sits upright. The one I have is pretty old...

    So looking at the one I have, it is located to the right of the fuel pump. So te one currently on there has 3 wires going to it...Well, the positive & negative and then a third connection that is like a line going somewhere...Was not able to track it tonight at it is in an awkward location and hard to get to...

    If I get this replacement switch, what do I do with this extra line? It seems the new switch only uses a +/- electrical connection and that's it...

    Also, I took a pic of this as I first thought it was the Oil pressure safety switch. If this is not it, what is it? Why does it have only one connection?



    I had also noticed there was this black wire running from my cockpit oil pressure gauge to no where...Should this wire go to that other connection on the other switch pictured above? Where should this wire go to (Pictured below)?

    1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
    1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)
  • ndutton
    Afourian MVP
    • May 2009
    • 9777

    #2
    As connected in the picture that does not appear to me to be an oil pressure safety switch, more like a low oil pressure alarm sensor. You mentioned three wires but I only see one wire and an oil tube.
    Neil
    1977 Catalina 30
    San Pedro, California
    prior boats 1987 Westsail 32, 1970 Catalina 22
    Had my hands in a few others

    Comment

    • jpian0923
      Afourian MVP
      • Sep 2010
      • 994

      #3
      Do you have a mechanical fuel pump or electric?
      "Jim"
      S/V "Ahoi"
      1967 Islander 29
      Harbor Island, San Diego
      2/7/67 A4 Engine Block date

      Comment

      • southcoasting
        Senior Member
        • Nov 2011
        • 164

        #4
        Originally posted by jpian0923 View Post
        Do you have a mechanical fuel pump or electric?
        As far as I know it's electric
        1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
        1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)

        Comment

        • southcoasting
          Senior Member
          • Nov 2011
          • 164

          #5
          Originally posted by ndutton View Post
          As connected in the picture that does not appear to me to be an oil pressure safety switch, more like a low oil pressure alarm sensor. You mentioned three wires but I only see one wire and an oil tube.
          Ah...On that switch I have pictured, that's the one I ask about that I'm not sure what it is...but your theory on being a low oil pressure alarm makes sense...

          The actual oil pressure safety switch that I mention I want to replace is not pictured since it's in an awkward location that I can even take a picture of...and that one is the one that has three connections going to it...

          If I can get in there today, I will take a pic so you can see what I mean...I have to take a panel off in order to get better access to it...
          1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
          1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)

          Comment

          • Marian Claire
            Afourian MVP
            • Aug 2007
            • 1769

            #6
            Yes. http://www.moyermarine.com/forums/showthread.php?t=1804 The first pic is a OPSS. Just like my old one. Dan S/V Marian Claire

            Comment

            • ndutton
              Afourian MVP
              • May 2009
              • 9777

              #7
              Southcoasting,
              Our typical OPSS has two wires, not three. All it takes is 12V+ in from the ignition circuit and 12V+ out to the electric fuel pump. There is no reason for a ground wire.
              Last edited by ndutton; 02-02-2012, 10:42 AM.
              Neil
              1977 Catalina 30
              San Pedro, California
              prior boats 1987 Westsail 32, 1970 Catalina 22
              Had my hands in a few others

              Comment

              • JOHN COOKSON
                Afourian MVP, Professor Emeritus
                • Nov 2008
                • 3501

                #8
                Use an ohm meter. A OPSS to the fuel pump will be normal open. An alarm switch will be normal close. The one with three wires may have both functions in the same switch.

                TRUE GRIT

                Comment

                • JOHN COOKSON
                  Afourian MVP, Professor Emeritus
                  • Nov 2008
                  • 3501

                  #9
                  What Type Of Oil Pressure Gauge Do You Have?

                  I had another look at the first picture in post #1.

                  Is the other end of the copper tube at the back of the oil pressure gauge? If so you have a direct read, mechanical gauge. If not where does the tube end?

                  If you have an electrical oil pressure gauge, and I hate to say this, the what appears to be an OPSS may be a misguided attempt at an oil pressure sending unit. Does the single wire end up at the back of the oil pressure gauge? You may need to disconnect the wire on the back of the oil pressure gauge and disconnect the single wire at the end in the picture and use an ohm meter and jumper wire to figure it out.

                  The black wire may be the ground wire for the instrument cluster. Can you get a picture(s) of the front and back of the instrument cluster that shows the wiring? I'll probably be able to figure it out if I can see a picture.

                  TRUE GRIT

                  Comment

                  • hanleyclifford
                    Afourian MVP
                    • Mar 2010
                    • 7020

                    #10
                    The oil pressure switch pictured in the first post is a NAPA sold item possibly a 6624. It is supposed to have 2 wires and should close the circuit at 7 psi and start the fuel pump or whatever. Where is the second wire?
                    Last edited by hanleyclifford; 02-04-2012, 08:00 AM.

                    Comment

                    • southcoasting
                      Senior Member
                      • Nov 2011
                      • 164

                      #11
                      OK...So traced back the two cables connected to the previously pictured gauge switch and it is indeed connected to a gauge...One is an oil line (copper one JOHN COOKSON mentioned) connected to gauge, the other being connected to a ground it looks like...The one cut cable is coming from this same gauge and should be connected to this switch...So that solves that...at least for now...I'll find out if something crazy happens in a few months with that gauge and know why that one cable was cut...

                      I may just get a new gauge and not wait to find out...

                      And I did manage to get some angled pics of the actual OPSS and it has three connections...One must be positive, the other negative, and the third (one on right pointing to middle fuel pump connection) is connected to the middle connection of my Facet fuel pump.

                      Check the pic of the OPSS below:


                      And the pic middle connection of the fuel pump I'm talking about:
                      Last edited by southcoasting; 02-02-2012, 03:59 PM.
                      1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
                      1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)

                      Comment

                      • southcoasting
                        Senior Member
                        • Nov 2011
                        • 164

                        #12
                        Originally posted by ndutton View Post
                        Southcoasting,
                        Our typical OPSS has two wires, not three. All it takes is 12V+ in from the ignition circuit and 12V+ out to the electric fuel pump. There is no reason for a ground wire.
                        So I'm assuming once I get the new OPSS from Moyer, I can find out which one is ground on the existing switch and eliminate with to go with the typical 2 wire connection...
                        1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
                        1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)

                        Comment

                        • hanleyclifford
                          Afourian MVP
                          • Mar 2010
                          • 7020

                          #13
                          I cannot think of any reason why one would have two oil pressure switches for one fuel pump unless a PO was trying to eliminate that tangle near the fuel pump. I suggest you start over with your own design knowing that it is only necessary to ensure that the fuel pump stops running when there is no oil pressure (that is, engine shuts down but ignition switch is still in the "on" position). I would go with the front switch and eliminate that thing that you had so much trouble getting a picture of. A wire from the "ign" on terminal on the key switch to one blade on the OPPS (either) and a second wire to pump+ should do it. If you need a "cranking" override we can discuss that later.

                          Comment

                          • southcoasting
                            Senior Member
                            • Nov 2011
                            • 164

                            #14
                            Originally posted by hanleyclifford View Post
                            I cannot think of any reason why one would have two oil pressure switches for one fuel pump unless a PO was trying to eliminate that tangle near the fuel pump. I suggest you start over with your own design knowing that it is only necessary to ensure that the fuel pump stops running when there is no oil pressure (that is, engine shuts down but ignition switch is still in the "on" position). I would go with the front switch and eliminate that thing that you had so much trouble getting a picture of. A wire from the "ign" on terminal on the key switch to one blade on the OPPS (either) and a second wire to pump+ should do it. If you need a "cranking" override we can discuss that later.
                            Well, the one switch by itself is not really the OPSS that should be connected to the pump...

                            This one switch was connected to an old mechanical oil pressure gauge...At least that's how I understand it?
                            1971 Tartan 34C Sloop "NOVA LUNA", Rebuilt (2019) Fresh Water Cooled A4 (Bought boat in 2014)
                            1968 Tartan 27 Yawl "Destinada", rebuilt Old Lyme freshwater A4 (Sold boat in 2014)

                            Comment

                            • hanleyclifford
                              Afourian MVP
                              • Mar 2010
                              • 7020

                              #15
                              Yes, the picture does suggest the remote mounted oil pressure gauge and the "T" block with the pressure switch suggests an attempt to replace the other OPPS which is difficult to access. It is difficult sometimes to access the thinking of POs....The mechanical, tube fed oil pressure gauge would have no need for a pressure switch.
                              Last edited by hanleyclifford; 02-02-2012, 05:31 PM.

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