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Old 31-08-2019, 11:28   #16
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Re: Ever have an Oil Pressure Switch go bad?

If I were trying to claw off a rocky lee shore or trying to get out of the way of a 1000' container ship bearing down on me, I would glady sacrifice my engine while listening to a blaring low oil alarm rather than go dead in the water.
But that's just me.
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Old 31-08-2019, 13:08   #17
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Re: Ever have an Oil Pressure Switch go bad?

My old Perkins has a mechanical injection pump. Oil pressure switch can only sound an alarm. It cannot turn off the engine. To shut engine one pulls a cable attached to a cam or lever on the pump body.

I guess most engines of pre 1990 might be the same.
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Old 31-08-2019, 13:20   #18
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Re: Ever have an Oil Pressure Switch go bad?

Check if the low oil pressure switch is normally open, or normally closed. Replace with the same. Use a cheap auto pressure switch - just buy several of them if they should corrode faster. Paint or grease up exterior to lessen corrosion - don’t paint the threads or orifice.
Keep the safety feature of fuel pump/engine shut off with oil pressure faults. It will probably save your engine at some point.
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Old 31-08-2019, 14:15   #19
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Re: Ever have an Oil Pressure Switch go bad?

My first ever sailboat ride was on a Lafitte 44 down in Puerto Vallarta, MX. It had a Peugeot diesel that had blown up from no oil. The was no warning buzzer. I knew nothing about boats but I helped the guy put a rebuilt Peugeot back in the boat, still no buzzer. We took off for La Paz and it ran out of oil again just before Mazatlan. The guy just happened to notice the gage bouncing on 0. Added oil, but it blew up again motoring into La Paz. I think he was on his way to California.
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Old 31-08-2019, 18:40   #20
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Re: Ever have an Oil Pressure Switch go bad?

The universal diesel series of M25ís started out with the fuel pump on when ever the ignition switch was on. Then changed about the XP time to have it interlocked with the op switch. So yes no problem with rewiring.

Many engines will continue to run after the lift pump turns off depends on where the level is in relationship to the on engine pump.
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Old 31-08-2019, 23:27   #21
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Re: Ever have an Oil Pressure Switch go bad?

Was in the Gulf last month, 20 miles off Sabine Pass in light air when Westerbeke 35B choked then died.. started back up, then died. Seemed like a fuel/air problem. Spent lots of time and trouble running that down,, changed primary and secondary filters, etc., (not fun since wind did pick up) only to eventually (read: day two) find that the crimped wire connection to the oil pressure sending unit had come loose which simulates no oil pressure and kills the motor. Started right up and ran fine after wire was reconnected. I only tell this story so that others may profit from putting that sending unit and wire, not always easy to see, towards the top of the check list instead of the bottom, esp if you have an older motor or one that has been rebuilt or worked on by men that don't always crimp with gusto.
What I don't get is, however, even w the current cut to my elec fuel pump, why wouldn't there be enough fuel going to injector pump via gravity feed since the bottom of my fuel tank sits a good 2 feet above that intake line and the engine had been running for hours before the wired dropped ?? Any thoughts? Thanks, Pappy
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Old 01-09-2019, 05:44   #22
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Re: Ever have an Oil Pressure Switch go bad?

Sounds like some of you treat the engines like many women I have talked to about the similar scenarios when driving a car. If the oil pressure light comes on or the car overheats they just keep driving until it completely stops or they get to their destination cooked engine or not.
You might be able to run an overheating engine for a while (maybe minutes). But running an engine without oil pressure can be just a matter of seconds before it locks up and is a throw away or st best a major rebuild.
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Old 01-09-2019, 06:31   #23
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Re: Ever have an Oil Pressure Switch go bad?

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But running an engine without oil pressure can be just a matter of seconds before it locks up and is a throw away or st best a major rebuild.
I disagree with your statement about seconds to lockup. Have you personally ever seized an engine? I'm betting that you haven't since it doesn't happen that often.

For the most part, the oil "pressure" that you read on the gauge is really the back pressure from the clearances in the bearings but primarily from the back pressure resulting from the spring tension in a pressure relief valve inside of the engine. If your pressure drops below the setpoint of the pressure switch, it doesn't mean that you don't have oil flow. If you have a 15 psig pressure switch, and the pressure dropped to 10 psi on the gauge, you could run that engine for a very long time and may not experience any damage. I've done it. A good deal of lubrication is the result of splashing and sloshing anyway. There is a conservative factory of safety built into the normal running pressure.

I wouldn't shut down my engine due to an alarm (but I would check my gauges first) only to watch my boat drift onto the rocks or be hit by another ship. If I could get to safety first, I would try. The engine be damned.

If the pressure switch is wired into the ignition, and it shuts me down, I don't have a choice. It "saved" the engine and I lost the boat.
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Old 01-09-2019, 09:53   #24
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Re: Ever have an Oil Pressure Switch go bad?

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Check if the low oil pressure switch is normally open, or normally closed. Replace with the same. Use a cheap auto pressure switch - just buy several of them if they should corrode faster. Paint or grease up exterior to lessen corrosion - donít paint the threads or orifice.
Keep the safety feature of fuel pump/engine shut off with oil pressure faults. It will probably save your engine at some point.
this, above.... It's under $8 for an automotive version, but also check pressure rating on old one before you buy. They can range from 3-5psi up to 20-25psi. Too low and the alarm/fuel will go off when oil hot and at low revs. Like when returning to the dock. I wouldn't defeat the fuel shut off function, if you're worried of the switch going bad again, when you are running and with good oil pressure, you could rig a simple toggle switch across the oil switch terminals to keep the pump operating.
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Old 01-09-2019, 10:39   #25
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Ever have an Oil Pressure Switch go bad?

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Originally Posted by waterman46 View Post
My old Perkins has a mechanical injection pump. Oil pressure switch can only sound an alarm. It cannot turn off the engine. To shut engine one pulls a cable attached to a cam or lever on the pump body.



I guess most engines of pre 1990 might be the same.


They are almost all mechanical injection pumps, common rails differ.
The electric pump just functions as a feed pump to provide pressurized fuel to the injection pump, most all engines will still run without a feed pump but as they are having to suck fuel itís possible that they can cavitate, and cavitation will cause premature wear on the pump so almost all engines have a feed pump, my Yanmar and likely your Perkins have mechanical feed pumps, that do not of course have low oil PSI protection.
Itís the same as a watermaker , which has a feed pump to supply pressurized water to the high pressure pump.
I would have no problem bypassing the low oil pressure switch, often itís as simple as connecting the wire to ground, usually an oil pressure switch is normally open, when there is pressure it closes and supplies a ground path for the electric pump, usually connecting that wire to ground and the pump will now run whenever the ďignitionĒ is on.
Very easy to confirm with a multimeter too before you do anything.
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Old 01-09-2019, 12:07   #26
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Re: Ever have an Oil Pressure Switch go bad?

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you could rig a simple toggle switch across the oil switch terminals to keep the pump operating.
Best suggestion yet! Best of both worlds. You normally have the protection but also have the option to bypass it quickly in an emergency to keep the engine running.
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Old 14-09-2019, 21:35   #27
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Re: Ever have an Oil Pressure Switch go bad?

Had an oil pressure switch fail. Pumped all of the engine oil out into the bilge. Luckily the alarm sounded just long enough to alert me that there was a problem. Thus ensued an interesting set of events that were not all bad.
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Old 15-09-2019, 10:20   #28
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Re: Ever have an Oil Pressure Switch go bad?

I had an oil pressure switch fail on a car. I luckily saw the oil on the driveway before my wife drove it to the grocery store.
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Old 15-09-2019, 12:50   #29
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Re: Ever have an Oil Pressure Switch go bad?

I installed a remote mount filter. Advantages are numerous, larger oil filter, easier and no mess to change, can pre-fill filter when changing etc.
This of course blew the O-ring out at the block and adapter interface.
Assuming I must have put it together wrong somehow as the O-ring was not damaged, I cleaned up everything and put it back together and set out again.
Of course it blew the O-ring out again.

I learned a couple of things, first always have at least as much oil as one oil change requires, so if something happens, you have plenty of oil.
Carry an extra filter as an oil filter can blow an O-ring too, rare, but it happens in a one in a million times.
Carry a threaded pipe plug so that in case your oil pressure switch, oil pressure transducer etc blows you can plug the hole.
Yanmar often uses a BSP thread, and not an NPT thread, so good luck finding a plug, maybe just carry a spare sender / switch.
I have a plug only because I took it out of an oil galley to install an oil pressure gauge. So if you take a plug out, donít lose it, itís worth itís weight in gold.

Donít trust cheap oil filter relocation kits. You get what you pay for.
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Old 03-11-2019, 14:34   #30
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Re: Ever have an Oil Pressure Switch go bad?

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Originally Posted by RickMorgan View Post
On my Westerbeke 44Cs, weíve struggled for several seasons with sudden loss of power in either (catamaran) engine. After numerous fuel filter changes and troubleshooting efforts, I called in a mechanic. A quick look and a call to a Westerbeke factory technician, and he comes back with a $35 part. A new oil pressure switch!

He said the Westy tech told him the fuel pump is wired to the oil pressure switch, although why was not revealed. If the switch fails, the fuel pump quits, simulating a fuel starvation event.

For you technical folks, any reason I canít (1) wire the fuel pump to some other circuit? (2), would any there be any difference if I used an auto parts switch (cost $8 vs, Westerbekes $35 part. A newer version in the Westerbeke catalog costs $95.). The switch activates an alarm if the oil pressure drops, or in my case, the switch fails.

I look forward to your responses. None from Westerbeke!
Almost all switches, and relays Westerbeke uses are Cole Hersee, and commonly available. Iíve had switches go bad and Iíve had the tabs break. IN A PINCH you can jump between the two wires that go into the switch. But every comment in this thread about it being an engine protection device are absolutely true. If you have to jump the wires, check your oil level before doing so and monitor your oil pressure continuously- after all, thatís what we did before oil pressure switches.
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