Another question Yanmar 4BY2-150 oil pressure readings

[CaptainT]

Where can I buy the oil pressure sensor?

 

[scross]

I purchased our new oil pressure sender here:
Kelly Tour-Parts
Cook Engines, Portland, OR
Ph # 503-289-8466
Fax # 503-286-2836
website:http://www.cookengine.com

For my 4by2-150 the new sender was about $270 shipped. The new sender has worked perfectly with about 100 hours on the engine since replacement.

 

[rpmerrill]

This may be repetitive. I apologize.
I saw my name mentioned regarding a post on this subject. I couldn't find it but I'll take the risk of possibly repeating myself.

The oil sender has a diaphragm that moves a sweep arm with increasing pressure. The arm simply rubs over a wound coil of wire and the further it goes the higher the resistance value that goes into the computer. The higher the resistance the higher the pressure reading. When there is a break in that fine coiled wire, the resistance goes up and it shows an unrealistically (impossible) high pressure.

When you start the engine, and just sit at idle and then cruise out of the marina the oil pressure is pretty low and you might not see the fault in the reading. BUT if you power up while the engine is still cool the pressure can get pretty high. Ig it is up in the area of the fine wire fault, bam, you've got real high or infinite oil pressure readings.

If you happen to get sufficiently warmed up before you pour on the diesel, the pressure never gets high enough to reach the faulty wire area. Thus a good reading.

I tested and confirmed all these theories with a gauge installed with the sensor using a tee. Trying to remember...On start up at idle the cold oil pressure might be 40-50 psi. Then at higher rpms still running cool, it might go to 75+ psi. But as soon as the temps get up in the high 100's it drops back to 60-65 psi and everything is happy. That is why the "faulty" reading goes away. The broken wire in the rheostat is somewhere above the normal pressure. (don't ask me why it broke up there) I had the exact same problem on a gas tank sensor in an antique car back in 2014 so diagnosis of all this was easy.

I don't leave the pressure gauge installed with the sensor. I have a new sensor. Like someone mentioned above I think it's best to keep the sensor close coupled to the engine and avoid the chance of a piping leak caused by vibration. The new sensor is working fine.

I have only been left with two questions after I went through this in 2016.
1.) Why does this sensor cost so much? Lots of sensors on the market that cost a LOT less.
2.) Why do I get a low oil pressure alarm on the first 5 seconds of start-up but I didn't get an alarm when the sensor went wonky? I think I even disconnected the sensor while under way and got no alarms. AND I still got the start-up alarm with no sensor at all. I never got a good answer on that back in 2016.

 

[knotflying]

Where can I buy the oil pressure sensor?

J-Way has pretty good prices and service and they can sell in Ohio. https://www.j-wayent.com/

 

[BB marine]

I have only been left with two questions after I went through this in 2016.
1.) Why does this sensor cost so much? Lots of sensors on the market that cost a LOT less.
2.) Why do I get a low oil pressure alarm on the first 5 seconds of start-up but I didn't get an alarm when the sensor went wonky? I think I even disconnected the sensor while under way and got no alarms. AND I still got the start-up alarm with no sensor at all. I never got a good answer on that back in 2016.

I believe there is an oil pressure switch Open/close that the alarm is activated by. And there is an oil pressure sensor that the gauge gets it's readings from. Many engine manufactures do this. Yanmar 120650-39270 sensor, 165001-98630 switch located at oil filter housing.

I looked for a VDO auto sensor, which typically sell for $40 or so, but could not find one with the same size/thread pitch as the one on the Yanmar. I guess having everything proprietary is how Yanmar makes its money. If you find one from VDO please let us know! I would not mind changing a $40 unit every other year. Otherwise I’m just going to ignore the temporary high pressure readings if they recur and consider my boat haunted....

Pressure Gauge Adapter, 1/8 BSP Male & Female, 1/8 NPT F Tee #1073-001 This fitting allows you to still use the existing sensor and thread an additional VDO sensor. Or this to just install a VDO gauge.https://www.hoyetractor.com/storeimages/OGA-1.jpg (OIL PRESSURE GAUGE ADAPTER - NPT TO "YANMAR" THREADS) description Product Description
•••••
IF YOU WANT TO USE A STANDARD 1/8 NPT OIL PRESSURE GAUGE IN YOUR YANMAR TRACTOR THEN YOU WILL NEED THIS ADAPTER. YANMAR USES A THREAD THAT IS VERY CLOSE TO NPT BUT IS NOT THE SAME AND WILL NOT WORK.
FEMALE THREADS = 1/8" NPT
MALE THREADS = "YANMAR" THREADS

 

[scross]

Brian,
Thanks for the hoyetractor.com link to the thread adapter! You are a true gentleman and a scholar!! Just ordered one of the thread adapters for the spares trunk!
Even though our replacement genuine Yanmar $$$ oil pressure sender seems to be doing just fine it’s nice to know that I have less expensive replacement options should there be another sender problem in the future!

 

[knotflying]

Brian,
Thanks for the hoyetractor.com link to the thread adapter! You are a true gentleman and a scholar!! Just ordered one of the thread adapters for the spares trunk!
Even though our replacement genuine Yanmar $$$ oil pressure sender seems to be doing just fine it’s nice to know that I have less expensive replacement options should there be another sender problem in the future!

You may want to check the clearance from the top of the sensor in place and the metal cover that protects the engine. That fitting may push it up too much to clear the cover.

 

[BB marine]

You may want to check the clearance from the top of the sensor in place and the metal cover that protects the engine. That fitting may push it up too much to clear the cover.

The fitting measures 1" in length. If the fitting plus the sender length prohibits it to fit without modifications to the shroud the may be another option. Catalina Yachts uses a custom made sending unit on the Yanmar powered boats.
https://www.catalinadirect.com/images/p ... L01_lg.jpg

This custom made oil pressure sender may used in Yanmar Diesel engines aboard boats built by Catalina Yachts. The standard Yanmar engine uses a sender with non-standard threads and an impedance matched to European instruments. In order to use American instruments aboard your Catalina, you must replace the standard Yanmar sender with this custom sender.

These replacement oil pressure gauge senders are machined to fit Yanmar's threads and the impedance matches that of our #T2023 oil pressure gauge.
https://www.catalinadirect.com/
Go to site select a boat ,select electrical, sending unit can be found with description.

There was a Ranger 27 with a Yanmar that had this issue last year at the marina. The Ranger dealer spent the summer trying to get the oil pressure reading correct. He wouldn't use the boat unless it was fixed. It isn't fixed at the end of the season. I found these remedies but he wanted to have the Yanmar OEM gauge working. I agree but at the cost of the OEM and the continual failures that this component seems to have, I thought this was an option. I think his disappointment of this he sold the boat. It wasn't at the marina this year.

 

[knotflying]

I took a look at the image you listed. I seem to remember that the 4BY2 unit had two terminals. Sometimes I take the position that since I am doing the work myself and saving money I will just go with the OEM part and bite the bullet.

 

[BB marine]

I took a look at the image you listed. I seem to remember that the 4BY2 unit had two terminals. Sometimes I take the position that since I am doing the work myself and saving money I will just go with the OEM part and bite the bullet.

I agree with using the OEM. I would first elect to replace the sending unit with OEM. If I found the reliability of the system to be erratic then I would be looking for another resource . The issue with the OEM in many cases it fails and is pricy. There are many failures to the oil pressure sending not only on the Tugnuts forum but many others, along with the marine repair facilities. In some cases it's not as simple as just changing the sending unit. That was the case with the R27 that I spoke with, replaced the $200+ sending unit and it failed. For this reason some have elected to by-pass the OEM sender and use an after market. The custom sender from Catalina is a standard one wire sender with different impedance so a different gauge would have to be used. This is explained in the description of the sender. The Yanmar gauge will not work with this sending unit. This would be a conversion. If you want to use the Yanmar gauge you must use the OEM sending unit. If you elect to use a less expensive, conventional 12 volt sending unit that is common in the marine industry the custom sending unit from the Catalina web site is an option. If the adapter (listed in a previous post) allows clearance any standard sending unit will work but once again a different gauge will have to be used. I can't confirm this statement because I don't have a Yanmar but I believe as stated before in the previous post the Alarm system for no or low oil pressure will not be affected by not using the OEM oil pressure sender. There is a separate switch oil sender that activates the alarm.
I believe this may confirms that the pressure oil sensor and alarm switch sensor are different circuits.

2.) Why do I get a low oil pressure alarm on the first 5 seconds of start-up but I didn't get an alarm when the sensor went wonky? I think I even disconnected the sensor while under way and got no alarms. AND I still got the start-up alarm with no sensor at all. I never got a good answer on that back in 2016.

 

[vertigo]

I agree with using the OEM. I would first elect to replace the sending unit with OEM. If I found the reliability of the system to be erratic then I would be looking for another resource . The issue with the OEM in many cases it fails and is pricy. There are many failures to the oil pressure sending not only on the Tugnuts forum but many others, along with the marine repair facilities. In some cases it's not as simple as just changing the sending unit. That was the case with the R27 that I spoke with, replaced the $200+ sending unit and it failed. For this reason some have elected to by-pass the OEM sender and use an after market. The custom sender from Catalina is a standard one wire sender with different impedance so a different gauge would have to be used. This is explained in the description of the sender. The Yanmar gauge will not work with this sending unit. This would be a conversion. If you want to use the Yanmar gauge you must use the OEM sending unit. If you elect to use a less expensive, conventional 12 volt sending unit that is common in the marine industry the custom sending unit from the Catalina web site is an option. If the adapter (listed in a previous post) allows clearance any standard sending unit will work but once again a different gauge will have to be used. I can't confirm this statement because I don't have a Yanmar but I believe as stated before in the previous post the Alarm system for no or low oil pressure will not be affected by not using the OEM oil pressure sender. There is a separate switch oil sender that activates the alarm.
I believe this may confirms that the pressure oil sensor and alarm switch sensor are different circuits.

2.) Why do I get a low oil pressure alarm on the first 5 seconds of start-up but I didn't get an alarm when the sensor went wonky? I think I even disconnected the sensor while under way and got no alarms. AND I still got the start-up alarm with no sensor at all. I never got a good answer on that back in 2016.

I can confirm BB's conclusions that the oil pressure alarm is triggered by a separate oil pressure switch from the oil pressure sender. The oil pressure switch on all Yanmar BY2-series engines is located on the port side of the engine just below the base of the oil filter housing. On the 6BY2-260 in my 2012 R-29, that switch is mounted horizontally, threaded into an adapter block that is itself secured to the filter housing by a banjo bolt (17mm hex head) threaded vertically up into the housing. Looking at the Yanmar parts catalogues for BY engines, the adaptor block is not shown, and the pressure switch is shown as threading directly into the underside of the filter housing.

It appears that this non-stock adaptor block is used to make pressure switch replacement easier in this installation with close clearances to the engine mount, and is prone to loosening from engine vibration, so regular maintenance checks should probably include confirming that the banjo bolt is tight and has not worked itself loose. In my case, when I reached down to feel for the location of the head of the banjo bolt, the mere light pressure of my fingertips was enough to loosen that bolt and allow oil to leak into the bilge on next startup. (Not a fun cleanup.)

Regarding the exorbitantly-overpriced OEM Yanmar oil pressure sender: there is no good reason to pay $275 for a replacement sender in a Yanmar box, particularly on an engine that is no longer under factory warranty, especially so since that sender is in fact a VDO unit. When I removed and inspected the original sender from my 6BY2-260, it was plainly marked as a 32/6 unit, 0-10 bar pressure range. VDO cross reference documentation confirmed that this is a floating-ground unit operating at 10-180 Ohms, with an M14x1.5 thread, a common unit on both Asian and European engines. (This sender is common to Deutz, for example.)

So, if you want to replace this sender with another VDO unit of matching specification that is readily available in North America, then you can use a VDO 360-430 unit (approx. $50 from Amazon and other online retailers), which is identical in all respects except for the mounting thread, which is 1/8" NPTF, so you'll also need a Male M14x1.5-to-Female 1/8" NPTF adapter, which will be threaded into the engine with a crush washer.

$50 is much better than $275 for a part that is reputed to fail with some regularity, and it will work identically with your Yanmar instrumentation.

If I understand correctly from obsessive reading elsewhere on the topic of pressure sender failures, the main cause of those unit failures is engine heat and vibration. Racing engine modifiers commonly relocate the oil pressure sender off of the engine to improve its reliability. So, while I was changing over my oil pressure sender to the newer unit as a part of a diagnostic project to eliminate intermittent low oil pressure alarm events when cutting the throttle from cruise power to idle, I added fittings and braided stainless oil pressure line to move my pressure sender to a bulkhead near the engine hatch, and added a tee block and mechanical pressure gauge beside the pressure sender. Now I check the actual oil pressure anytime by simply looking under the engine hatch rather than wonder if the resistance-derived reading on the gauge is accurate.

These upgrades cost less than one new sender in a Yanmar box, and the peace-of-mind in having a steam gauge to confirm oil pressure is priceless.

As to the unnerving intermittent low oil pressure alarm at idle after cruise power, mine was resolved by changing the oil three times within a month after acquiring our boat in November, and switching from 5W-30 to 10W-30 full synthetic oil. Now the steam gauge confirms that the oil pressure never drops below 14psi at full operating temp (186f).