Oil Pressure Warning Light Works, Pressure Gauge Shows Zero

[Gone2long]

Am posting this inquiry as a separate thread as nobody so far has attempted to address this particularly relevant issue.

Wondering what folks think about the fact that the oil pressure warning light on my diesel seem to be working but the oil pressure gauge reads zero? There are two warning lights: they, and an alarm, indicate that there is a low battery charge and low oil pressure when the ignition is turned on. This seems normal, as in an older automobile.

Then, when the diesel engages. the warning lights, and alarm, go off and do not go on again as long as the engine is running. This would suggest that the warning lights are working and that the engine actually has sufficient, if perhaps a bit low, oil pressure and that the charging system has sufficient amps.

If my oil pump is actually working the diesel is getting oil, and the compression is not critically low, I can worry about the gauge functioning later. Right now, I need to confidently run the engine to charge my batteries and move to a place where I can dive the hull.


All advice greatly appreciated.


G2L

[Wotname]

Yep, all's good while lights stay out and the alarm is quiet. See my last post on your other thread for a little more detail.

The fact the lights and alarm come on before engine start and after engine shutdown indicates the warning system is serviceable.

The gauges have been added later and who knows if the job was done properly or not; worry about them later

[delmarrey]

Hi AB,

If the motor has a rocker arm cover with an oil fill cap, you could pull the cap with the motor running to see inside. Oil should be squirting all over inside the cover.

The other thing would be to loosen the oil sender so it wiggles in the threads, but not too much, and start the motor. Oil should be squirting out around the sender.

Either way you'll know if you have oil pressure. BTW if you buy a new sender/gauge be sure to get a match to each other. There are two different series, Euro and USA.

Del

[Wotname]

Originally Posted by delmarrey

Hi AB,

If the motor has a rocker arm cover with an oil fill cap, you could pull the cap with the motor running to see inside. Oil should be squirting all over inside the cover.

The other thing would be to loosen the oil sender so it wiggles in the threads, but not too much, and start the motor. Oil should be squirting out around the sender.

Either way you'll know if you have oil pressure. BTW if you buy a new sender/gauge be sure to get a match to each other. There are two different series, Euro and USA.

Del

Del, FWIW, going by the OP's detail on his other thread, it seems this engine is a 3GM30; certainly it is a 3 cylinder 27 HP, 20 year old Yanmar.

[Gone2long]

Originally Posted by Gone2long

Am posting this inquiry as a separate thread as nobody so far has attempted to address this particularly relevant issue.

Wondering what folks think about the fact that the oil pressure warning light on my diesel seem to be working but the oil pressure gauge reads zero? There are two warning lights: they, and an alarm, indicate that there is a low battery charge and low oil pressure when the ignition is turned on. This seems normal, as in an older automobile.

Then, when the diesel engages. the warning lights, and alarm, go off and do not go on again as long as the engine is running. This would suggest that the warning lights are working and that the engine actually has sufficient, if perhaps a bit low, oil pressure and that the charging system has sufficient amps.

If my oil pump is actually working the diesel is getting oil, and the compression is not critically low, I can worry about the gauge functioning later. Right now, I need to confidently run the engine to charge my batteries and move to a place where I can dive the hull.


All advice greatly appreciated.


G2L

Wot and Del,

I will check under oil cap for squirting. Seems like that should be the case regardless of engine type, and, as per Wot's replies on my previous thread, seems like all is functioning "normally", if not perfectly.

Keep in touch, and thanks so much for your help.

G2L

[sailorboy1]

When my oil pressure gage stopped working a couple of years ago it was that the gage failed (I replaced the sensor and the gage, but it was the gage).

When my water temperature gage failed I again replaced the gage and the sensor, but it was the gage.

Far as having faith that the oil pressure pump is working; if it wasn't and you have run the engine and it didn't fail, the pump is working.

[DougR]

The fact that the oil alarm light goes off and the buzzer becomes silent indicates that there is at least 6 or 8 Lbs. of oil pressure, as that is normally where the alarm is set to make electrical contact.

If you want to be more certain of the condition of the lubrication system, get a mechanical oil pressure gauge and screw it into the opening where the oil pressure sender is currently located. Then run the engine at various RPM levels and you can clearly see where things stand. Normally oil pressure senders have 1/8 inch pipe threads, but you can check that when you remove the sender.

To do a quick check of the gauge and sender, turn the key on, remove the wire from the sender and momentarily touch the wire to the engine block ( ground). This will cause the gauge needle to "peg" or go full scale. If it does peg, it tells you that the gauge is operational and the wiring from the panel to the sender is good, so the problem probably lies in the sender. If there is no movement of the gauge needle, it means that there is no power to the gauge, the gauge is bad, or there is an open circuit between the gauge and the sender.

Good luck!
DougR

[Gone2long]

Originally Posted by sailorboy1

When my oil pressure gage stopped working a couple of years ago it was that the gage failed (I replaced the sensor and the gage, but it was the gage).

When my water temperature gage failed I again replaced the gage and the sensor, but it was the gage.

Far as having faith that the oil pressure pump is working; if it wasn't and you have run the engine and it didn't fail, the pump is working.

Sounds logical from what everyone else has mentioned. I have run the engine for maybe 6 hours in the 2 mos or so that I have owned her and have encountered no issues underway. However, I did not check the gauges until the most recent start up. Upon start up, the engine ran for 20 minutes without incident, but that is when I noticed no gauge activity.

As a first time owner, I just want to make sure I don't trip over my own feet.

Thanks for helping to clear the companionway.

G2L

[Gone2long]

Originally Posted by DougR

The fact that the oil alarm light goes off and the buzzer becomes silent indicates that there is at least 6 or 8 Lbs. of oil pressure, as that is normally where the alarm is set to make electrical contact.

If you want to be more certain of the condition of the lubrication system, get a mechanical oil pressure gauge and screw it into the opening where the oil pressure sender is currently located. Then run the engine at various RPM levels and you can clearly see where things stand. Normally oil pressure senders have 1/8 inch pipe threads, but you can check that when you remove the sender.

To do a quick check of the gauge and sender, turn the key on, remove the wire from the sender and momentarily touch the wire to the engine block ( ground). This will cause the gauge needle to "peg" or go full scale. If it does peg, it tells you that the gauge is operational and the wiring from the panel to the sender is good, so the problem probably lies in the sender. If there is no movement of the gauge needle, it means that there is no power to the gauge, the gauge is bad, or there is an open circuit between the gauge and the sender.

Good luck!
DougR

Thanks Doug. Every bit of info helps me to begin understanding the system.

Regards,

G2L

[Kenomac]

We had the same problem on our boat two years ago on a Yanmar 100hp. After replacing two oil pressure sending units and then the gauge, the problem turned out to be electrical. Could never really find the source of the electrical short, so we ended up running a new wire from the sending unit to the gauge. Problem solved. Good luck.

[sailorboy1]

From my experience wiring problems involving the engine always seem to be at a harness connection.

[Terra Nova]

Originally Posted by Gone2long

...Wondering what folks think about the fact that the oil pressure warning light on my diesel seem to be working but the oil pressure gauge reads zero?...

I'm thinking that you should be testing the gauge, sender and circuit, rather than risking expensive damage to your engine.

[MBWhite]

I'll agree with Terra Nova here. While it sounds like you don't have an oil pressure issue as none of the other alarms go off and your engine is not making excessive rattling sounds, marine engines have a different operating schedule and environment than most land-based counterparts.

DougR has good advice on troubleshooting, and it could be something simple such as a bad connection on the sending unit or gauge and a firm wiggle can bring it back.

[boeing1]

when is the last time of oil and filter change,
had a friend that had same problem, oil pressure drops to zero, but oil light did not come on, oil and filter change fixed his,possible obstrution in sending unit for oil pressuse, however, as others suggested first check condition of wiring....

[clyde]

hard wire another gauge, and see if it works? has to be the kind that works with your engine system...clyde