Oil Pressure Safety Switch questions???

[hanleyclifford]

In 99% of cases Neil is right about not needing the override circuit from the "R" terminal on the solenoid to get the fuel pump running before oil pressure is achieved. In fact on my boat I don't want fuel pump or ignition until at least 7 psi oil pressure is attained. FWIW, sometimes the "R" terminal is used to provide a coil resistor override to "goose" the voltage to the ignition during cranking.

[magi]

How bad of an idea is running with the OPSS jumped out ?

[msmith10]

The purpose of the OPPS is to turn off the fuel pump if the engine is not running, thus preventing the pump from forcing fuel into the carb and potentially spilling into the bilge. If I were away my home port and the OPPS malfunctioned, I would bypass it to get home, then fix it. I would not leave it bypassed as this would create a potentially unsafe condition, would certainly void the insurance, and is just an unseamanlike thing to do.
It's such an easy fix- screw out screw in.

[joe_db]

Originally Posted by 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.

I have a manual button for the override. If I have run the fuel out after shutdown, I use it. If the engine was just turned off still showing fuel pressure, it is not needed.

[capnward]

Just a reminder, if you have a mechanical fuel pump (there I go again!), there is no need to override or bypass anything electrical to get fuel pressure with the engine off. You just manually pump the bail underneath the pump until the resistance disappears and your fuel pressure gauge reads 3 or so. This way the engine will start sooner and not have to crank for a while to get fuel from the tank to the carb. And as Joe said, if you have been running recently there will be adequate fuel in the carb to start.