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1999 Bryant 182 low oil pressure switch

C

CRaymond

New member
My Mercruiser 4.3 Alpha 1 will start right up but will stall in 10 seconds. Bypassed the oil pressure switch after reading about similar post by jumpering the leads with a paper clip and it will start and stay running. Bought replacement switch at NAPA to replace old one that was PN 87-864252 and leaking oil out the end. New part number 87-4252A01 and had to splice new ends on it. Put it all together and I still have the same stalling issue? If I bypass the switch with paper clip it runs fine. Also only hear the file pump when I bypass the switch.
 
My system includes an oil pressure sending unit that tees off of the oil sensor switch. My oil pressure gauge reads Reads 40 pounds and increases as I increase RPMs. I checked the output of the new oil pressure switch And it reads infinite homes when the engine is off and drops to 62 homes when the engine is running, Is it possible the Napa part is not compatible with my mark cruiser 4.3 L?
Bt Doctur said:
system is based on oil pressure , do you have any? Remove the electrical sender and install a gauge to see.
Click to expand...
 
Oil safety switch is for like 8psi which you get with about half a turn of the engine. Dying after a few moments probably isn't related to the oil safety switch itself since replacing it didn't solve the problem. However, the wires that go to/from the safety switch are indeed critical to keeping Mr Lump humming along. Strongly suspect that there is loose or corroded connection somewhere in that wire run. You get 'er going and vibration shakes something loose, breaking the happy flow of electrons. Drifting.
 
if you mean 62 ohms when running, that's too much resistance to allow the fuel pump to run.....so there is a bad connection or you got a pressure sender unit instead of a switch.....

also, typing in the old part number on the ME.com part search page give a different replacement part....so I'd suspect they gave you the wrong part....
 
o2batsea said:
Oil safety switch is for like 8psi which you get with about half a turn of the engine. Dying after a few moments probably isn't related to the oil safety switch itself since replacing it didn't solve the problem. However, the wires that go to/from the safety switch are indeed critical to keeping Mr Lump humming along. Strongly suspect that there is loose or corroded connection somewhere in that wire run. You get 'er going and vibration shakes something loose, breaking the happy flow of electrons. Drifting.
Click to expand...

So why would bypassing the oil safety switch by jumper ring the two leads together solve my issue? As I stated in my previous post when I jumper and bypass the switch my engine run fine and does not stall?
 
Because (as makomark pointed out) the jumper is a low ohm connection. 62 ohms is too high by a factor of 100.
 
CRaymond said:
So why would bypassing the oil safety switch by jumper ring the two leads together solve my issue? As I stated in my previous post when I jumper and bypass the switch my engine run fine and does not stall?
Click to expand...

I think what your missing here is,

The oil pressure switch is on/off. Open/closed at a certain oil pressure.

A sender varies resistance which shows on the gauge.

So if you replaced old switch with a sender then it is not a on/off swith

When you jump the wires you are making a closef/on connection.
 
better off with this
71n9v1RUMGL._SL1500_.jpg
 
kghost said:
I think what your missing here is,

The oil pressure switch is on/off. Open/closed at a certain oil pressure.

A sender varies resistance which shows on the gauge.

So if you replaced old switch with a sender then it is not a on/off swith

When you jump the wires you are making a closef/on connection.
Click to expand...

OK that makes sense, the part I got from NAPA says Sender/Transmitter part number OP6751SB, sounds like wrong part.
 
My low oil pressure switch has two terminals on it so I assume it would be the one in the second image? Do you have a PN? Assuming you agree that the part number for the new NAPA part I provided is for a sending unit and not for a switch. As in they (NAPA) gave me the wrong part?
 
Better places to buy BOAT parts than a primarily CAR parts store. Yes it can cost more at a MARINE store but then again they will usually give you the correct part. If you have the time, this forum's sponsor has the correct part.

RE: "Can anyone confirm that the NAPA part number OP6751SB is not the correct part? According to NAPA website, it is a sending unit that comes with or without a gage. "

Most of us here will assume that the NAPA site is correct for NAPA parts and it is, as stated, a "sending unit". NOT a switch.
 
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sandkicker said:
Better places to buy BOAT parts than a primarily CAR parts store. Yes it can cost more at a MARINE store but then again they will usually give you the correct part. If you have the time, this forum's sponsor has the correct part.

RE: "Can anyone confirm that the NAPA part number OP6751SB is not the correct part? According to NAPA website, it is a sending unit that comes with or without a gage. "

Most of us here will assume that the NAPA site is correct for NAPA parts and it is, as stated, a "sending unit". NOT a switch.
Click to expand...

Just ordered the replacement switch from leaders RPM and will let you know the outcome once installed
 
As far as confirming.

The answer is in the description,

SENDING UNIT

A sending unit is the oil pressure gauge sending Unit.

NOT AN OIL PRESSURE SWITCH. IT IS A SENDING UNIT. (VARIABLE RESISTANCE WHICH SHOWS OIL PRESSURE ON THE GAUGE)

Any more questions?
 
Jack is correct...... you'll have two entirely different items.

The "switch" is known as a LOP Switch..... I.E., a Low Oil Pressure Switch that is N/O (normally open).
It closes the circuit once oil pressure reaches/exceeds it's rated pressure..... of which I believe is in the range of 7 or 8 psi.
Once the circuit closes, it operates the associated relay for the fuel pump.
Once it drops out of it's rated pressure range (i.e., stalled engine), it opens the circuit and interrupts power to the fuel pump's relay.


The oil pressure gauge sending unit is nothing more than a variable potentiometer..... not a switch!


I believe that this is a Hobbs oil pressure switch.
If so, and since it offers 3 terminals, it can be used as a N/O or as a N/C switch.

71n9v1RUMGL._SL1500_.jpg
 
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