Oil Pressure alarm problem

[AlamedaKen]

We recently purchased a 2010 R-29. The Yanmar engine alarm comes on indicating low oil pressure during docking. The engine at idle rpm and possibly related to the seemingly unrelated use of the thrusters. The engine was serviced using Yanmar oil and the oil pressure sender on the engine replaced to no avail. During operation the oil pressure appears normal otherwise. Is this known to be a wiring issue? Or an engine software issue? Any hints would be appreciated.

We have had this boat since June and do not feel confidant in using the boat due to this issue.
AlamedaKen and Jen

 

[captstu]

Ken and Jen

The actual oil pressure in the engine is converted to the pressure on the gauge through combination of mysterious software and strange hardware.

The only way to tell for sure that I know of is to get an inexpensive mechanical oil pressure gauge and screw it directly on the engine in place of the Yanmar sender. That way you will know the real readings and can convert them in your mind to what you see on your Gauge. After the test you can put the original sender back in.

Operating the thrusters will cause a slight decrease in a perfectly operating engine RPM because of the small extra load placed on the alternator to provide electricity for the thrusters. This is normal and should be of no concern. If however your engine RPM is set low or the gauge is set low, then, the combination may cause an alarm when you engage the thruster.

You could just assume your idle is set to low and set up a tiny bit. But I would try mechanical oil pressure gauge just to be sure. A good mechanic should have in her toolkit and they’re not very expensive.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[Hydraulicjump]

If you search back through this site you will find multiple references to this issue, but it was usually on R-27's with the Yanmar 4BY 180 engine. Having had this problem, it took major sleuthing to find it. In my case it was a combination of problems with the ECU and, as I later discovered, a weak ground. The weak ground caused all kinds of issues for the electronics.

One of the things I strongly recommend is to start by cleaning up your grounding cables, including making sure that each connection is polished until it shines bare metal. This includes contacts on the grounding buss. In my case, the culprit (well, one of the culprits) was a poor connection where the ground cable attached to the engine. I pulled it off and found that it was painted, making the ground weak.

Chances are very slim that you have actual low oil pressure, but the previous advice is correct. You don't know until you put a mechanical gauge on it. When I replaced the ECU we had to put the mechanical gauge on and recalibrate the oil pressure readings. That shut up the alarms.

Good luck.

Jeff

 

[trailertrawlerkismet]

You've obtained great advice from Stuart and Jeff, this is one of the true benefits of the Tugnuts Forum. When you ultimately correct your situation please post back to all of us what the cure was so we can learn from your predicament.

Jim F

 

[rpmerrill]

The strange part of this is that if you disconnect the pressure sender it doesn't cause an alarm.
I had a sender problem last year and replaced the sender. But I never had an alarm.
BUT during the diagnosis experiments, I disconnected the sender and used a tee with the gauge and the sender. Still no alarm.

At the time I posed the question: Where and how does the engine ECU measure and alarm the oil pressure. Nobody knows.

 

[captstu]

The engine test every sensors at start up time. If the sensor is missing or disconnected, the engine control unit just deletes the indicator from that place on the gauge. So the gauge reads nothing not zero .

This is Yanmar's way of telling you the sensor is missing.

 

[rackline]

Your comment about this possibly being related to thruster use is similar to what we've experienced this first season with our 2009 29 with the same Yanmar. However, in our case more than a couple of seconds of thruster use triggers the low voltage alarm that won't clear until the engine is shut off. Restart and all is good. Maybe unrelated, but this engine seems very fussy about power.

 

[knotflying]

I have a 4BY2-180. Very similar engine to the 6BY2. There are a few things that can be going on and probably the last is an actual low pressure. I would probably go in this order: 1) It could be the sender itself. So a replacement could be needed. You can check the sender with an ohm meter. I do not have the exact numbers, but as RPM increases you should see a change in ohms. If you do not see a change the sender is shot. 2) Make sure your connections that power the ECU are in absolutely good shape. They should be running to your engine battery, remove them and clean them. 3) There was a service bulletin on the grounding for the sensor that pertains to all BY2 engines. Run a new wire from one of the sensor terminals to the paddle wheel ground wire on the wire harness going to the software control box. I believe there is a post with the actual service bulletin. The bulletin number is YASA2014-005-M. If you can't find it PM me with your e-mail address and I will send it. This bulletin also includes an update of the software. This requires sending the unit in for a replacement that has been updated. This was a warranty item so hopefully you can still get this done under warranty.
And then again you can go the route that Stuart went and just install and idiot light.
Let us know how you make out.