Oil Pressure Sensor Wiring

[c130king]

Backstory: When I first bought Polaris three years ago I used to always get the low oil pressure warning horn when I turned the key on. The sound would go away once the motor was started and oil pressure came up to normal. Just as it was supposed to. But then at some point several months later the warning horn went away. Did a little digging and couldn't find the issue. A few months later I overheated the motor (that sort of thing happens when you run the motor without the raw water through-hull open... ). Anyways when that happened I go no warning horn...but I did get the light. So I replaced the horn. But still no low oil pressure warning tones. I just sort of forgot about it.

Yesterday couldn't get the motor to start. Pushed the starter button and nothing happened. Did some troubleshooting and poking around by the solenoid and found some disconnected wires and what I think is a circuit breaker where they were attached. Looks like the two wires were connected together on one terminal of the circuit breaker and the other terminal was connected to the ignition solenoid (or maybe the electric fuel pump???).

Anyway, I stripped those two wires and wired them together to see what happens. Lo and behold I now get the low oil pressure warning horn when I turn the key on.

So here is a picture of what I think is a circuit breaker. The two wires (both are green on my boat) went to the one terminal and that flat connector was connected to the terminal on the solenoid (or fuel pump...now I am not sure where I took it from).

I seem to recall that there is some sort of safety setup on the MX25 so that if you lose oil pressure the engine will shut down. But not quite sure about that.

Can anyone offer some explanation? Is that indeed a circuit breaker and is it 15amp? I found a replacement 15amp. How/where should it be connected?

Thanks for any info.

Cheers,
Jim

 

[JK_Boston_Catalina310]

I will have to look on my boat when I get home to confirm, but I think you are talking about the 10 amp breaker that is between the preheat solenoid and the buzzer and electric fuel lift pump. See the attached.

 

[c130king]

That may be it. So this "Preheat Solenoid"...thought it was the starting solenoid. We were trying to jump across the solenoid and getting no response. Is there a start solenoid as well? Is it down on the starter (and difficult to get access to?)?

Would love a picture of where this circuit breaker connects to ensure I mount it at the proper point.

And what exactly is it's purpose?

I currently have those two wires twisted together. Seems to power my warning horn to give me low oil pressure indication. So why connect it to a circuit breaker.

Just confused over how this is supposed to work and what it is supposed to do.

But thanks for those diagrams.

Cheers,
Jim

 

[KZW]

JK,

If you can take a picture, I'd like to see it!!!

 

[peter_ms]

The fuel pump should not run unless either the starter or preheat solenoid is engaged OR the engine is running as proven by the oil pressure switch.
I am looking at the wiring diagram on my phone so it is hard to follow but I will have another look when I get home

 

[c130king]

Can anyone tell me what the purpose of this circuit breaker is and will a 15-amp breaker work? That is what I have.

Thanks,
JIm

 

[JK_Boston_Catalina310]

The purpose would be to protect the wire. If you read the wiring diagram you have 10 AWG wire going into the preheat solenoid. The 10 AWG wire is protected with the 20 Amp breaker shown on the diagram (the one with the red button near the on board fuel filter). The wires coming off of the breaker are 14 AWG. So it seems like they stepped down from 20 Amp to 10 Amp due to the reduction in wire gauge.

That being said, if you reference a wire and fuse sizing chart (I like the one from Blue Sea Systems) they recommend either a 25 Amp or 30 Amp fuse for a 14 AWG wire in a bundle in an engine room. So the 10 Amp was slightly undersized. The 15 Amp you have should work.

But the bigger issue is why that melted down in the first place? Was there a loose connection?

 

[c130king]

Nothing melted. The wires just broke off. The unit is just "yukked" up. No overheating/melting.

But I still don't quite understand why the circuit breaker is connected as it is...one post to the preheat solenoid and one post with those two wires together.

I have the two wires connected together...not connected to the preheat solenoid...and everything seems to be working fine.

I guess the part I am not quite getting is why do the two wires need to be connected to the preheat solenoid in the first place. I don't have them connected now and I get the low oil pressure warning and the motor starts and runs normally...at least it seems to.

Cheers,
Jim

 

[2 OLD PIRATES]

This may be a little off topic but it's about a buzzer. When I turn the Key a buzzer sounds. I start the engine but the buzzer keeps buzzing. It comes from the gauge panel. Any ideas what it could be?

Cheers
2 Old Pirates

 

[peter_ms]

This may be a little off topic but it's about a buzzer. When I turn the Key a buzzer sounds. I start the engine but the buzzer keeps buzzing. It comes from the gauge panel. Any ideas what it could be? Cheers 2 Old Pirates

Broken tab on Oil Pressure switch or no oil or temp switch lead shorted to ground somewhere.

 

[JK_Boston_Catalina310]

Broken tab on Oil Pressure switch or no oil or temp switch lead shorted to ground somewhere.

I second the broken tab. Had this happen to us a couple of years ago.

 

[JK_Boston_Catalina310]

Nothing melted. The wires just broke off. The unit is just "yukked" up. No overheating/melting.

But I still don't quite understand why the circuit breaker is connected as it is...one post to the preheat solenoid and one post with those two wires together.

I have the two wires connected together...not connected to the preheat solenoid...and everything seems to be working fine.

I guess the part I am not quite getting is why do the two wires need to be connected to the preheat solenoid in the first place. I don't have them connected now and I get the low oil pressure warning and the motor starts and runs normally...at least it seems to.

Cheers,
Jim

From the wiring diagram, the wire goes from the "S" terminal on the key switch, to the preheat solenoid, from the preheat solenoid to the buzzer and the fuel lift pump. So my first thought is what happens when you turn the switch forward?

What should happen is that this circuit is activated and the buzzer should sound while the fuel lift pump pumps. Do you hear the clicking noise of the fuel lift pump? If not it could make for a problem next time you change your fuel filters.

 

[peter_ms]

From the wiring diagram, the wire goes from the "S" terminal on the key switch, to the preheat solenoid, from the preheat solenoid to the buzzer and the fuel lift pump. So my first thought is what happens when you turn the switch forward? What should happen is that this circuit is activated and the buzzer should sound while the fuel lift pump pumps. Do you hear the clicking noise of the fuel lift pump? If not it could make for a problem next time you change your fuel filters.

Agreed.
Under normal running circumstances the fuel lift pump is powered by the "I" or run terminal of the ignition switch; through the oil pressure switch contact, which is Closed when the engine is running i.e. has oil pressure... That circuit is protected by the 20A main circuit breaker on the rear mounting plate on the engine.

Despite the happenstance that the C310 will start and run without the fuel pump, (given more than about 3/8 of a tank and you aren't heeled to port), the starting circuit incorporates a bypass to the "not running=no fuel pump" protection circuit.
Following the drawing earlier in this thread; the preheat solenoid is powered directly from the starter terminal with only the main battery 150A fusing (not shown in the drawing but adjacent to the batteries in their compartment). Universal designed in this 10A circuit breaker in this bypass loop, to protect the fuel pump and associated wiring when cranking with glow plugs.

With that circuit breaker bypassed; the engine will start normally; but C130King risks a wiring fire next to the fuel lines if the fuel pump fails in a shorted mode. Unlikely but possible. Since it is normally protected by a 20A breaker with other connected loads, a 15A breaker is probably OK but Universal picked 10A for a reason.

Given that the circuit is only powered in preheat/glow plug mode, and given that diesel is extremely hard to ignite; the risk of a serious fire is minimal using a 15A fuse; however anyone who has seen an un-fused small gauge wire short to ground will attest that a fuse is definitely required.

Peter

 

[c130king]

I have the CB and will be installing it on Monday. I think I understand most of what you guys are saying. I am not sure my lift pump is working or is working normally. I do not use that pump to bleed the air out of the fuel lines when changing fuel filters (which I just did about a week ago). I use the manual pump on top of the Racor.

These two wires in question have been disconnected for about 2+ years (pretty sure...I wasn't getting a low oil pressure horn for time) and yet everything the motor started and ran.

My fuel level is rarely below 1/2 tank.

Once I get it wired back in on Monday I willl see if I can use the lift pump to bleed air out of the fuel lines.

Thanks again for all the words of wisdom.

Cheers,
Jim

 

[c130king]

Follow-up...sorry for the delay.

Hooked the two wires back to the new 15amp CB and then connected the CB to the third post on the solenoid. And now my electric fuel pump works. Fuel pump hasn't been working for a long long time...but the motor worked just fine.

Can clearly hear the pump working when I hold the key in the pre-heat position. And I get the low oil pressure warning horn when the key is first turned on. Glad to know that things are working properly again.

Now if I can only figure out what is wrong with the A/C unit and the stereo...it is always something.

Thanks again for all the information and assistance.

Cheers,
Jim