Oil Pressure Safety Switch questions???

[southcoasting]

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)?

[ndutton]

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.

[jpian0923]

Do you have a mechanical fuel pump or electric?

[southcoasting]

Originally Posted by jpian0923

Do you have a mechanical fuel pump or electric?

As far as I know it's electric

[southcoasting]

Originally Posted by ndutton

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...

[Marian Claire]

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

[ndutton]

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.

[JOHN COOKSON]

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

[JOHN COOKSON]

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

[hanleyclifford]

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?

[southcoasting]

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:

[southcoasting]

Originally Posted by ndutton

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...

[hanleyclifford]

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.

[southcoasting]

Originally Posted by hanleyclifford

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?

[hanleyclifford]

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.

[JOHN COOKSON]

Originally Posted by southcoasting

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...

The ground side or circut is usually kept seperate from the hot circut. To have the ground side and hot side on the same switch is well......atypical.
The cut wire may have been the ground wire to the instrument cluster. You can see this for yourself or post a picture. Each gauge should be grounded. If the wire that was cut does come from the gauge cluster as a ground wire the other end went to engine ground or a buss bar then on to battery ground.
Have you consulted the "drawings and schematics" section of the forum?

TRUE GRIT

[hanleyclifford]

If the switch has three terminals it is most unlikely any of them have to do with ground. It is more likely two of them are one side of the switch providing two + inputs to run the pump - possibly one from the ignition circuit and an override from "R" on the starter solenoid.

[southcoasting]

Yeah, on the gauge itself, there are three connections, one is already grounded...The other is not a ground that I would assume goes to the switch and third connection is the copper oil line...

[hanleyclifford]

What's needed here is a wiring diagram. Neil, are you on station?

[ndutton]

Originally Posted by hanleyclifford

What's needed here is a wiring diagram. Neil, are you on station?

It's my pleasure.

[edwardc]

Originally Posted by southcoasting

Yeah, on the gauge itself, there are three connections, one is already grounded...The other is not a ground that I would assume goes to the switch and third connection is the copper oil line...

If your gauge has a copper oil line going to it, it's a mechanical gauge, and needs no power to function. The only leads going to it should be for the illumination lamp. One wire should go to ground, and the other to someplace that is energized to +12 when the ignition switch is turned on.

[hanleyclifford]

The diagram posted by Neil shows the basic wiring for the fuel pump but does not include the override circuit from solenoid "R". Since your OPSS has three terminals and thus possibly the override, additional wiring details may be needed. Thank you, Neil; as always ready with the good stuff.

[ndutton]

It's my opinion the override adds unnecessary wiring complexity to a basic A-4. There is ample residual fuel in the carb bowl to get the engine started without any help from the fuel pump. Once started the oil pressure rises so quickly it seems the fuel pump starts instantly (I have a fuel pump indicator light on my engine panel so I keep a close eye on it).

If you're a keep it simple sort, I'd avoid the start switch override altogether. Simpler to wire in the first place, simpler to troubleshoot later.

[southcoasting]

I see...That makes sense...

Thanks everyone...

I will try to simplify this setup and see what I come up with...Will keep you guys posted...

[southcoasting]

Thank you all SO MUCH! I was able to troubleshoot and figure out what is what with your help...You guys are the "A-BOMB"!

So, I was able to do quite a few things recently to get this thing ready for next week's on "the hard start". Trying to get the boat launched by end of April...

While getting things ready (normal maintenance as recommended here before first season start), I realized Hanley and others were right about the OPSS wiring...One wire was coming from the starter and the other from the coil...So I will be wiring the new replaced switch with only the +Coil wire and remove the +Starter wire to keep it simple...

I also confirmed the black wire from the first picture coming from the oil gauge seems to be a power cable, prob for the gauge light as edwardc suggested...

Buying some batteries this weekend and looking try to start this thing for the first time next week...Will keep you guys updated on the progress...