Halloween oil pressure drop and alarm

[Hydraulicjump]

Perhaps, since it is Halloween, I should just say my boat is haunted.

Last week when coming back to the dock to put the boat on the trailer the low oil pressure alarm went off and there was very low pressure (below 10 psi; I have around 30 psi at idle with a warm engine). I turned off the engine and drifted to the dock and tied up. First thing, I checked the engine compartment expecting to see oil all over the place. Nope, clean as a whistle. I had also checked the oil before departure: dead in the middle of the port side dipstick.

Now how to get the boat onto the EZ Loader....so I started it back up, got 25 psi at idle, and idled it up to the trailer. When I pushed it to 2000+ to move it up onto the trailer the pressure crashed and I shut it down, winching the rest of the way.

Andrew and Kenny suggested that I check the engine ground, since this causes problems for oil pressure alarms. The internet was pretty useful, as was this site, indicating a likely failed oil pressure sending unit. My sissy mechanic said he wouldn't work on it because it probably involved the need to read the codes and then futz with the ECU which he says he can't do. Knotflying was a great help and suggested that I put an ohm meter on the sending device to see if it is changing resistance with rpm, and to then put a mechanical gauge on to see that I actually have oil pressure. The Yanmar repair manual (if you don't have this, it is worth downloading) basically pointed the finger at the sending unit.

Went out there today armed with all the necessaries: multimeter, jumper cable to bypass the engine ground, hose to shove into the strainer (boat's on a trailer), beer...

Wouldn't you know it, the thing ran fine. Checked the oil: perfect. Started it up and oil pressure jumped all the way to 80 psi. As the engine warmed it slowly came down. I ran the rpm up and down multiple times and the pressure adjusted with it (no need to bust out the meter). At about 115-120 degrees the idle pressure settled down to its normal reading. I did not try to get it up to its normal running temperature of 189 since that would have taken forever without the ability to put a load on the engine.

So now what? I went back and found the grounding buss had modest corrosion on it. I cleaned that up. Cleaned the ground contact with the engine (no corrosion at all). Same for the batteries. What I DIDN'T do was remove the beauty covers and clean the contacts on the sending unit. I will do that next time I guess. I also need to get it up to full running temp to see what the pressure reads.

So, I wonder when this "ghost" will reappear. Boo!

Happy Halloween

Jeff

 

[Dog Islander]

You made good use of your time on the boat by cleaning the corrosion from the electrical contact that you were able to get to. They needed to be done anyway. I hope the beer was made use of too. Sounds like you had a spook on board. Happy Halloween!

 

[walldog]

Hi Jeff,

I would be concerned with the alarm going off. When my sending unit was bad, I had erratic oil pressure indications, but no alarms. Yanmar factory rep told me that if the alarm did not go off, my oil pressure was OK. He said the alarm will only sound if oil pressure is actually low. The sending unit on the top of engine sends info to the network for the chartplotter, etc. The alarm works from a different source. Putting a mechanical gauge on will give the best indications. Good Luck.

Herb,

 

[MissJill]

Hi Jeff,

I would be concerned with the alarm going off. When my sending unit was bad, I had erratic oil pressure indications, but no alarms. Yanmar factory rep told me that if the alarm did not go off, my oil pressure was OK. He said the alarm will only sound if oil pressure is actually low. The sending unit on the top of engine sends info to the network for the chartplotter, etc. The alarm works from a different source. Putting a mechanical gauge on will give the best indications. Good Luck.
Herb,

Herb and others - read your oil pressure reply - I've been having the same issues - have replaced the sender with expensive Yanmar 'exclusive' part (which is a BMW sender much cheaper but must use an extender to fix -- then of course its too high and wont clear the engine step plate.)
Borrowed a mechanical pressure sensing unit and the oil was within limits hence no alarm no worries.

I'm thinking about a mech oil pressure gauge -believe I only need a positive lead and a ground lead (which I could take from a DC component at the helm (lights, anchor, VHF_ circuit/s) . any opinions on this approach and what type/make of gauge would work.
THX
MissJilly

 

[MissJill]

Perhaps, since it is Halloween, I should just say my boat is haunted.

Last week when coming back to the dock to put the boat on the trailer the low oil pressure alarm went off and there was very low pressure (below 10 psi; I have around 30 psi at idle with a warm engine). I turned off the engine and drifted to the dock and tied up. First thing, I checked the engine compartment expecting to see oil all over the place. Nope, clean as a whistle. I had also checked the oil before departure: dead in the middle of the port side dipstick.

Now how to get the boat onto the EZ Loader....so I started it back up, got 25 psi at idle, and idled it up to the trailer. When I pushed it to 2000+ to move it up onto the trailer the pressure crashed and I shut it down, winching the rest of the way.

Andrew and Kenny suggested that I check the engine ground, since this causes problems for oil pressure alarms. The internet was pretty useful, as was this site, indicating a likely failed oil pressure sending unit. My sissy mechanic said he wouldn't work on it because it probably involved the need to read the codes and then futz with the ECU which he says he can't do. Knotflying was a great help and suggested that I put an ohm meter on the sending device to see if it is changing resistance with rpm, and to then put a mechanical gauge on to see that I actually have oil pressure. The Yanmar repair manual (if you don't have this, it is worth downloading) basically pointed the finger at the sending unit.

Went out there today armed with all the necessaries: multimeter, jumper cable to bypass the engine ground, hose to shove into the strainer (boat's on a trailer), beer...

Wouldn't you know it, the thing ran fine. Checked the oil: perfect. Started it up and oil pressure jumped all the way to 80 psi. As the engine warmed it slowly came down. I ran the rpm up and down multiple times and the pressure adjusted with it (no need to bust out the meter). At about 115-120 degrees the idle pressure settled down to its normal reading. I did not try to get it up to its normal running temperature of 189 since that would have taken forever without the ability to put a load on the engine.

So now what? I went back and found the grounding buss had modest corrosion on it. I cleaned that up. Cleaned the ground contact with the engine (no corrosion at all). Same for the batteries. What I DIDN'T do was remove the beauty covers and clean the contacts on the sending unit. I will do that next time I guess. I also need to get it up to full running temp to see what the pressure reads.

So, I wonder when this "ghost" will reappear. Boo!

Happy Halloween

Jeff

Jeff - I got the same prob. What gauge did you use (buy).
JKelly

 

[Hydraulicjump]

So sorry to hear that you are having the same problem. There was a long saga after this Halloween unpleasantness that involved a replacement of the ECU, a clean up of the grounding buss and an added cable to better ground the engine. Others have put mechanical oil pressure units on and found that the problem is--most of the time--electrical and was unique to the Yanmar 180 4by2 system. I purchased a Yanmar sending device and installed it (easy to do), but it did not solve the problem.

And you can search through the website, but I am pretty sure Yanmar is not supporting this problem anymore under warranty.

With help from the factory (who I bought the boat from) I eventually got someone to replace the ECU and recalibrate the oil pressure readings from the ECU (very nice guys in Stockton).

That said, I want to encourage you to start with completely overhauling your grounding system. This involves cleaning everything on the grounding buss that can possibly be cleaned until it shines, every cable between the engine and the ground, every negative on the batteries, etc. I honestly think this is a weak grounding system that once corrosion sets in discovers the weaknesses in the rest of the design. Kind of the way water or the ocean always finds the weakness in planning and design. Look at Oroville Dam here in California.

Others here can chime in. The Yanmar is a really great engine with, in my view, some weaknesses in the electronics.

Report back!

Jeff

 

[knotflying]

Poor grounding is definitely an issue. You need to have impeccable grounding otherwise you start to get erroneous alarms. I ran a ground directly from the engine battery to the engine block. There are to many connections from ground to engine the way it is wired from the factory. I also did the grounding direct to the sensor per the service bulletin and prior to that another ground was installed to the wire harness by a Yanmar mechanic when it was under warranty. I believe I was one of the first with this problem (erroneous oil pressure alarm) and it took several calls over a few days back and forth to Japan for then to resolve the issue.