Normal Oil Pressure

[TFrere]

I need some help. I recently installed a slightly used (250 hour) Yanmar 3JH4E in my boat. I am having problems with either the oil pressure gauge, the sensor, or the wiring between the two. As soon as the engine starts the gauge goes to maximum. My mechanic says it is not the actual oil pressure and the gauge is giving a false reading. He asked me to find out what normal oil pressure was on this engine at idle, 1500 rpms, and 3000 rpms. I tried calling the Yanmar distributor but have not been able the get this information. Can anyone help?
Thanks in advance.

 

[woodster]

call charlie at bells marine in p cola he will help you 850 455 7639 or kloudie may tell you

 

[Gunni]

about 45 psi. You should have him tap the oil pressure sensor port with a mechanical pressure gauge. The Yanmar oil pressure gauge is electric and the harness has several places where you can lose continuity.

 

[Charles Erwin]

Locate Yanmar service manual. Find Lubrication System chapter. In lubrication system chapter look at capacities table. These values are clearly marked.

Verify for your motor. However - for example - the GM series normal pressure is about 42 - 58 psi. (One doubts yours is much different but verify anyway.)

By the way normal pressure will decline over time as main bearings wear. Also pressure will be lower at normal operating temperatures, higher at cold startup; lower at idle, higher at normal RPM.

Over pressure - very rare - and is controlled/adjusted via oil pressure bypass valve.

Charles

 

[Gunni]

Oh, another thing, you may have the wrong oil pressure sender in you motor. My 3JH4E did not come with an oil pressure gauge, just the idiot light / buzzer. I added a digital gauge system to my boat and had to add a second pressure sender to make it work. Sounds like you are trying to feed a pressure gauge with a idiot light/buzzer sender.

 

[TFrere]

I had the Yanmar distributor, laborde products, supply the panel with gauges and replace the sensors to gauge sensors. The strange thing about it is both the gauge and sensor have the same ohm range. However, the resistance is going down in the wiring from the sensor to the gauge. Seems impossible for the resistance to drop but that's what we are reading. We believe it may be a faulty ground.

 

[kloudie1]

Probably a good idea to verify it with a mech gauge if chasing wires and connections doesn't work.. Too much pressure could be a plugged filter or a pressure control bypass that is plugged. A mechanical cheapie gauge from Pep Boys or another auto parts place can be had for under $20. Wwon't be absolutely accurate but will put you in the park. Sensors: some sensors operate backwards from others (0 press=high ohms vs 0press = 0 ohms).. if the gauge and sensor are same brand and model, probably not an issue here
Sorry to hear that ya having issues with the new powerplant.. Hope ya locate it quickly.

 

[TFrere]

Thanks guys.
Claude,
Labordes ran the engine with their panel and reported all in excellent condition including normal oil pressure. I believe it is something with the new panel. I will buy a mechanical gauge. I just don't know if they come with BST threads.

 

[kloudie1]

Looks like if there is a short in the sender or the sender wire, the gauge should read full scale.. This from Teleflex:



Oil Pressure System- Inboard & Stern Drive

1. To test the gauge, voltage from "I" to "G" terminal must be 10-16 volts DC, with no wire on "S" terminal. Gauge pointer should rest below the "0 PSI" mark. Next, connect the "S" terminal to the "G" terminal (leave "I" and "G" terminals connected). The gauge pointer should rest above the maximum pressure mark.
2. Sender resistance can be measured to determine the sender's correct operation. Remove wire to gauge. Connect an ohmmeter to terminal of sender and to engine block. Approximate pressure sender resistance values are:
   • Zero pressure = 240 ohms
   • 1/2 gauge reading = 103 ohms
   • full gauge pressure = 33 ohms.
   • You will get half these values on a dual gauge sender.
3. If sender is shorted (0 ohms) gauge will read above full gauge pressure reading.
4. If sender has infinite resistance (open) gauge will read below 0 PSI.
5. If gauge reads lower than expected, was sealer used on the sender threads? (See illustration.)
6. The accuracy of the system (gauge & sender) can be 5 PSI at 40 or 50 PSI.
7. Use of pipe extenders to plumb both a sender and pressure switch (for horn or warning light) from one port is not recommended. Pressure readings will be accurate, but the weight added to the extended fitting of a vibrating engine may cause fatigue related break age.
8. Teleflex does not offer senders for metric threaded ports.

 

[TFrere]

Thanks for all the help. I purchased a mechanical gauge and found the oil pressure at idle after warm to be 55 psi. At 3000 RPM, the pressure was 82 psi. The Yanmar distributor said this is acceptable.