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connect the stock oilpressure meter to new 4,3 vortec engine

Garpen61

New member
I have installed a new Vortec egine in 1991 Bayliner 2052. I have a new oil pressure sensor that is connected to the fuel pump. when I try to find out how to connect the original oil pressure meter, using the striped cable, the needle jumps a bit backwards and stay there until i release the cable.

how should everything be connected. I have also read somewhere that the gas pump wouldn't start until the pressure has raised a bit while cranking the starter. Mine starts when I turn the ignition on. What is the correct way to do it.
 
the oil pressure gauge is completely seperate from the oil presssure sensor. None of the wires are to be interchanged!!
Did you purchase the correct one? thre may be a sensor, a sender or a switch?

The sensor and switch are both basically a switch, the sender is a variable resistor sending oil pressure in OHMs to the gauge.


The oil pressure sensor/switch controlling the fuel pump is usually located just above the oil filter. It should have two wires that go to it. One wire is power in and the other is power out which goes directly to the fuel pump (this is so when oil pressure is above 5psi) If no oil pressure then the sensor (or oil pressure switch) is open (no current flow)

So on your system there should be one wire that comes from one of the small starter termianl (purple with yellow stripe) and is connected to the (power out side) wire going to the pressure switch. This is what applies power when CRANKING the engine over. this is or may be hidden in the wire harness (the connection)

Once oil pressure has reached over 5 psi and the motor has started the oil pressure switch closes and alows current flow so when you return the key to the run position the fuel pump operates normally. The purple wire that should be going to the oil pressure switch (power in) side.

After looking at the schematics I have it seems there may be some specifics/differences about your year vs newer models.

So Need to know a few things

1. do you have a oil pressure sender and if so where is it located?
2. do you have a audio alarm system and if so find all the points of connection. (tan with blue stripe wire) shoul be at least two (over temp switch and no oil pressure switch ) no oil pressure may look like the sender but not sure.
3.follow the purple/yellow wire feeding the fuel pump and where does it go? It should be going to the oil pressure switch and if so where is the pressure switch?
4 oil pressure sending unit, Not sure where it is mounted so tell us that also, That should have a light blue wire going to it. Again this is the variable resistor device not a switch device so it should have a reading from the center terminal to the threaded portion in OHMS. the typical range is 40-60 ohms to 220-260 ohms. So you should be able to get something within that range.
If you measure it and it shows only a open (no continuity) or closed (full continuity) then it is a switch not a sending unit
 
1. Its a switch with 3 contacts, its placed where the originally sensor/sender was placed on the old engine, right side near the distributor cap.
2. No audio alarm
3. Long way from the boat right now, so I have to come back with an answer
4. I just have this new sensor as described above mounted, I don't know where to put the sender/sensor from the old engine, but that seems to be the correct way..?
 
You can not use a switch type sensor and connect it to a gauge. wont work.

So you say it is where it was on the old engine..............where is that?

The oil pressure SENSOR can be in a couple of different locations. either tee'd with the oil pressure switch or it will be a stand alone and in many cases is mounted on the back side of the intake manifold near the distributor.

Need to know this............


a sender will should only have ONE center tap for the wire.

A switch may have one or more connections.

Where di you get the sensor/switch?

Is it a Mercriuser part or aftermarket?

Also get the serial number so we can look up correct parts and placement.

I was looking at the parts structure and did you original motor have a electric fuel pump or mechanical fuel pump?

The new motor is most likley designed for a electric fuel pump.

If your original motor had a mechanical fuel pump your wiring harness does NOT support a electric fuel pump.

If you have the knowledge it can be rewired if this is so.........

need a lot more information...............way too much missing..........
 
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got to hand it to Merc to use the language of oil pressure sensor instead of fuel pump switch. Just so damm confusing to most people.
I`ve been using a N/O switch to power the fuel pump thru a relay. When the electric pump starts to bind up and draw more current it burns the switch contacts and kills the power to the pump. The new merc switch only has 2 wires .It can also be mounter here .This port can also be "T"`d for the no oil pressure alarm switch.
IMG_1953.jpg
 
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