Yanmar 4BY2 Oil Pressure

[knotflying]

I don't think moisture is necessarily the issue. The covers are there to protect all the plastic parts and wiring from damage if stepped upon. I would see if you can find a large metal cap from a gallon container maybe. One that had Thinners or such. Not sure if that diameter will be large enough. Then set it in some 4200 adhesive. However, If it was my boat I would spring for the OEM sensor and be done with it.
Did you see if there is a similar sensor supplied from BMW? As expensive as their parts are, they are less expensive than Yanmar and many of the 4by parts are BMW repackaged by Yanmar. The parts are often stamped with the BMW numbers.

 

[rpmerrill]

Yup a large metal cap was one idea I had. The more I think about it, I like the clear plastic Tupperware lid idea.
I did look into the BMW idea. A friend who has a BMW repair shop looked for a sender for me, but all he found was a single post (ground through the threaded connection) sender. At that time I was early in my search so I passed on that idea.

Now that all is said and done, Maybe I should have pursued that approach.

From what I have learned from all the posts in this string, there seems to be a lot of unknowns regarding the oil pressure sender issue. We don't seem to know why they use two wires (one being a ground - supposedly). During my investigations, disconnecting both wires did not trigger an oil pressure alarm. Some posts have said that there is another oil pressure monitor that triggers the oil pressure alarm but we don't seem to know where it is located.

Another strange thing I learned yesterday: The new oil sender was weeping a small amount of oil at the MPT threads. I took it out and tried a little teflon tape. That fixed the oil leak, but the oil pressure display was not working. Obviously an engine block ground is important. I cleaned off the teflon tape (most of it), reinstalled and everything worked great.

This has made me think about something I saw during my search of oil senders. Some of the senders with two wiring posts were listed as having a built in low pressure trip point for alarm purposes. Curious-er and curious-er.

 

[knotflying]

The other interesting point about the two wires is that when you do the service bulletin fix it is a ground wire that you are sending back to the paddle wheel. I thought that the unit physically being grounded via threaded to the block would not matter. It seems like it does matter. The whole thing seems to be a bit screwed up. They now have a 4BY3 I wonder if that is the fix for all the 4BY2 issues.

 

[tlkenyon]

The Original Owner of my R21 Classic installed an analog oil pressure gauge by screwing a brass tee into the engine block and attaching the OEM sensor (idiot light) and analog sensor to the tee. Partly because of the vibration of the engine at low RPM, the tee failed and dumped all the oil into the bilges in what seemed like a matter of just a few seconds...made a nice oil slick. A contributing reason for the failure (and maybe the primary reason) is that the engine block threads are metric and he used a SAE-threaded tee. It was a very close fit but not correct. Consequently, only a couple of threads were engaged and probably represented a weak-point for the failure. I removed the remnants of the tee threads and reinstalled the OEM idiot light sensor.

Lesson...use the correct threads and minimize the lever arm....and keep an eye on it.

 

[rpmerrill]

Very good point!

 

[CAPTCRUNCH]

Will $200 change my lifestyle. No, I guess not.... after all, I now own a boat ! Ha.

But it's enough diesel for a nice cruise on the Bay.

 

[rpmerrill]

Another VERY good point.
Greetings GADGET!
r

 

[rpmerrill]

Latest update:
Well, I guess you get what you pay for. The cheap sender with the 1/8" mpt adapter worked for a while then totally quit.

Joke's on me. Original sender is back, installed and working most of the time. Any pressure below ~75 psi, it works just fine, but when the engine is cold, and the oil pressure a bit higher, it registers pressures WAY higher 150+ PSI and occasionally it drops to zero (or no signal). The slidewire rheostat goes from zero to infinite resistance on a random schedule. That is a little unnerving especially when the engine is warming up. No alarms or problems, however.

So I'm back in the market for a real pressure sender. Tired of screwing with it. Are they available from Ranger? Or anyone find a good source? (I think someone on TugNuts had some for sale???)

 

[Brian B]

Here's another oil sender fluke. I recently changed the oil and oil filter on my Yanmar 150. Upon start up the oil pressure gauge was reading higher than normal. After warm up and accelerating it would read up to 175 PSI.
After consulting with Knotflying and checking the senders resistance it resumed normal readings although 2 PSI higher than it had been. After a short cruise it resumed the same PSI readings prior to the oil change. The service bulletin on the sensor was completed 2 years ago. I made sure the sensor wire connections were clean and applied Corrision X.

 

[rpmerrill]

That sounds like the classic rheostat coil failure inside the sender. At normal pressure, where the engine spends the most time, the slider tends to wear out the coil. During start-up when the engine is cold, the pressure goes higher and the slider moves up the coil. However because of the worn area, the resistance is higher than it should be and the outrageous pressure reading results.

Once the worn area completely gives way, you will get no reading at all until the oil pressure drops down to the "normal" area. Surprisingly the "no reading" condition doesn't result in an alarm. (Disconnect the wire(s) to your sender and you'll see.)

I'm guessing the "zero" resistance condition would give an alarm, but haven't tested it.

 

[captstu]

When I purchased my R-25, I had the service advisory installed - and I'm sorry I did. The "no charge" fix cost me about $1,000 in "mandatory" slip fees and resulted in a never ending under-pressure.

I put in a mechanical gauge - there was no problem.

I drove the boat back to my home slip, contacted Yanmar, and they referred me to a very nice, but not very capable, local dealer.

They worked on the engine for weeks! Were unable to correct the oil problems.

Finally, I removed the oil sensor and wiring and installed an idiot light that seems 100% reliable.

Yanmar then said I had to bring the boat to a service center on the other coast of Florida - but I had to pay for the trucking or drive it there myself.

If your oil system electronics works, leave it along. They don't know how to install the service advisory and won't read the advisory even when I deliver it with the boat.

This took place about a year ago - the engine is still running perfectly, the oil idiot light works as expected and I'm overall happy -= except for being out just over $1000.

 

[nzfisher]

Unfortunately I have found this level of service to be the norm for all but a few dealers. There seem to be very few competent mechanics at certified yanmar dealerships or, the good mechanics are in such demand for bigger projects they are not available for the warranty work. Finding a good mechanic is one of the most difficult aspects of boat ownership with inboard motors. This is especially true if you don't keep your boat at a boating mecca where there are multiple or large dealerships.