8.1 MPI oil pressure switch/sender

My port side engine runs at 40-43 PSI at 3,200 RPM. My starboard runs at almost 50 PSI at 3,200 RPM. I wouldn't expect it to be exactly the same but I would like to see it a little closer. So I want to rule out the oil pressure sender and gauge. Looking at the parts diagram there are two different kinds of pressure senders. An "SS" and a "DS" and there is also a pressure switch that looks like it only goes with the "SS". I don't want to have to run down to the boat and take a look at it. Is there anyway of know what type I have without a physical inspection?

SS & DS are Single Station and Dual Station Sender units for the gauges.

Switches are either ON or OFF and typically don't care how many helm stations exist....

Thanks Mark. As usual you are a big help.

Glad to help.....FWIW, the switches are typically used to indicate a setpoint exceedance.....either to the warning horn for overheat, low oil pressure, or the ECM....my guess is as designator like SS tied to a switch was an editorial oversight....

A quick check on your sender/gauge concern is to swap the sender wires at the gauges.....another item that can impact accuracy is the wiring of the gauges.....bad ground or B+ wires will induce errors.....

makomark said:

Glad to help.....FWIW, the switches are typically used to indicate a setpoint exceedance.....either to the warning horn for overheat, low oil pressure, or the ECM....my guess is as designator like SS tied to a switch was an editorial oversight....

A quick check on your sender/gauge concern is to swap the sender wires at the gauges.....another item that can impact accuracy is the wiring of the gauges.....bad ground or B+ wires will induce errors.....

Click to expand...

Thanks Mark. That was going to be my next course of action.

As far a checking the gauges, most use the American standard.....with power ON, a 33 ohm resistor between S (w/ no other wires connected) and GND should give you full scale and a 240 ohm resistor should give you the min scale reading.....sender usually have a 10% tolerance on them regarding accuracy...

... and given the gauge technology, not likely the gauge any better accuracy, therefore, sender plus gauge accuracy can be anywhere up to 20% off, or @ 40 psi, +/- 8 psi. Then you have to add in the tolerance for the voltage on the electrical system... and any variable losses in the wiring and connections.