low oil light

[Brian2]

Hello,

After motoring for a while (an hour or so as I come back to the mooring) I noticed recently as I idled down into neutral to coast to the mooring, my oil pressure light comes on. This is at about 1100 rpms. It goes off if I stay in neutral and idel up to 1300 rpms. It doesn't come on under power at 1300 - 2000 rpms, but will come on under poer at less than 1300 (after warmed up). How do I test to see if this is a faulty sensor, or if I have a problem? The oil is full, so I know I have oil. As I rev up slowly from idle to 1300, the light flickers and goes out.

Now, this may have always been happening, but recently I came back at dusk, so the light showed up brightly. It may have been coming on before and I just didn't notice it. I have a 1987 CD 28 with Universal M-18 diesel.

Thanks, Brian

[sharkbait]

Well I can think of two possible things. One, you could have a bad oil pressure sender. Or, you could actually have low oil pressure at idle rpm. You have a couple of options. One, replace the oil pressure sender and see it that corrects the problem. Two, install a oil pressure gauge and see what the actual oil pressure is. Or, tear down the engine and replace the oil pump.

[Brian2]

Thank you for your reply. Can I use a guage inplace of the light? Will a guage use the same sender wires? Brian

[JWSutcliffe]

No, the Universal low oil pressure light uses a pressure switch, not a sender. The switch is simply on-off, and will not work with an electrical pressure gauge. Install a mechanical gauge tee'd off the same port as the oil pressure switch. A word of caution - given the typically high vibration of these little diesels, it is best to mount the pressure gauge to a panel or bulkhead and not directly to the engine connection. If you do a remote mounting like this, use an orifice or capillary tube to make the connection between the engine and gauge. That way, if the tube fails, you do not pump all of the engine oil out before realizing it.

[Bob Ohler]

I would start by doing a complete oil and filter change. When was the last time you changed your oil? If you are using a multigrade oil, switch to SAE30 or perhaps SAE40, per the specs for the Universal M18. I prefer Rotella or Delo brands oil for diesels.

[Brian2]

I figured I would start with an oil/filter change which I will do Saturday or Monday. I change once a season, usually at the end of the season. I use HD30 SAE30 oil, per recommendation in the engine manual. Last time I changed the oil, I could only get the Advance Auto parts store HD 30. I looked around at many stores, but all stores were out of HD 30. I now have Castrol HD 30. I also ordered a new pressure switch. My dad used to be a car mechanic, and he said it is almost always a bad switch, not always, but almost always.

Thanks for the replies and help - Brian

[Paul Grecay]

It sounds like worn bearings. When bearing surfaces are worn and the oil is warm, the oil pump will not quite maintain enough oil pressure. The light will go on....as you rev up, the light will flicker and at higher rpm, the light will go out as oil pressure is increased.

[Brian2]

Worn bearings are exactly what I am concerened about. I hope to heck it is not worn bearings. I will change the oil and filter today, if that doesn't work, I'll change the pressure switch. If that doesn't work, I'll have to consider rebuild vs. new.

[tmsc]

Brian,

I agree check with a gauge and change the oil and filter. It sounds as if you are using HD automotive grade oil. If so you should really be using HDEO which is for diesels. Chevron Delo or Shell Rotella are two that come to mind. I use the straight weight Delo 400 which is more in line with the requirements of older diesels and have had great success with it.

[Paul Grecay]

I rebuilt the MD2B on my CD 28...it was a big job and very expensive...I did the work myself since I have had experience in rebuilding engines...(mostly old air cooled VW engines). The Volvo was not terribly different...except that it was a diesel...and raw water cooled...and alot bigger...and no electrical ignition...and...and....hmmm...I guess it really was alot different! After a few years of service, my "new" MD2B developed a new problem...the water pump seal allowed seawater into the crankcase....what a mess...bearing surfaces marinating in...no hope. To make a long story shorter, I next repowered with a Beta Marine and I love this little engine. Three cylinders and alot smaller....the old Volvo was great...but this one is much better. The volvo sounded like an old NYC bus....the Beta sounds like a sewing machine. In retrospect, I wish I had repowered right away with the Beta Marine (Kubota) instead of resurrecting the Volvo...I would have saved alot of money and enjoyed having a quiet, new dependable diesel right away without all the hassle and wasted time and effort.
I hope your problem is not main bearings, but it sure sounds that way to me....keep us all posted.

[Kevin Kaldenbach]

TEE into the sending unit and install a mechanical gauge that you can mount anywhere. It does not have to be where you can see it all of the time if your idiot light still functions just where you can take a gander when you are concerned. Don't mount it where there is viberation. Maybe out of the way in the engine compartment. If your oil pressure is good at a resonably higher rpm don't get too excited about needing a rebuild. Just dont let it sit for a long time at a real low idle.

[Paul Grecay]

Kevin is right about just keeping the rpm up...you can probably get a few good years out of the engine before it demands attention. One of the symptoms of worn main bearings is a low vibration....kinda like the lowest note on a pipe organ...something you can feel rather than hear....but with a diesel, it may be very hard to detect. When the engine is running at higher rpm underload, the oil pressure will be high enough. I would just keep using it until it won't hold pressure when running....then repower. You might be surprised at how long it lasts!

[tmsc]

Hey Paul,

I have been looking at the Betas for when my old Volvo finally bites the dust. How much modification did you end up having to do to make the swap especially with the bed and how did you end up with having to install a fuel return?

[Brian2]

Hello all,

I changed the oil pressure switch, and all seems fine now. The light does not come on at low rpms. I could only test it on the hard, running the engine with the water intake sucking from a barrel. As such, I couldn't put it under load, and so I only got the engine temp up to about 160. Under load it runs between 170 and 180. I would rev up and idle back down, and the light didn't come on, so I hope a faulty switch was the problem. Next April, well prior to launch, I will have a test guage put on to test the pressure. That will still give me enough time to make a major repair if needed.

Thank you all, Brian