Low Oil Pressure Yanmar 4JH2E Help

[smokey73]

I have 1994 Hunter 40.5 with a Yanmar 4JH2E with about 1250 hours with a 3 bade Maxiprop.

BACKGROUND - The diesel runs like a top, sounds great, doesn't smoke and doesn't use oil. It develops 3200 RPM even with the 3 blade prop and gets about 1.1 gal/hr at 2700 RPM cruise and about 1.0 gal/hr at 2400 RPM. The oil filler dipstick reads right at the upper mark. There is no indication of water or contaminates in the oil and in fact it looks remarkably clean and new. I've put about 50 hours on it since I got it moving it from New York to Annapolis.

On the survey about 3 months ago the surveryor indicated it read in the normal range as one would expect. However, now the pressure guage reads below the normal range when cruising and it looks like about 20 psig (or so I recall but I'm not at the boat right now.)

Does anyone have any ideas why it would do this. As a Navy Submariner I have always been taught to believe my indications so I am concerned by this. 1. The way it is running I wonder if it might be the guage or sender unit.
2. Also, since it doesn't smoke or use oil I wonder if it might be the pressure regulator on the oil filter housing or the pressure regulator on the oil pump or possibly the oil pump itself.

Any experience with this would be appreciated and any shortcuts for troubleshooting would also be appreciated. When I get back to the boat I plan on putting a local manual oil pressure guage on at the sender unit fitting to see what the actual pressure is to start - any other thoughts?

Does anybody know the fitting size and thread so I can have all that staged before I get there?)

Thanks in advance. I will be moving the boat from Annapolis to Beaufort SC by the ICW the end of this month or sometime in November so I want this sorted out before I take off.

Smokey

 

[whatfiero]

low oil pressure

have you changed your oil lately (since the drop in pressure) yanmars are real picky about the type of filter ya use and type of oil try using heaver weight oil and tee another pressure gauge into 1/4 inch threads for pressure switch

 

[smokey73]

I haven't changed the oil yet but I was planning on doing that. It has a Yanmar filter and I plan on putting in a Yanmar filter. I live in Beaufort SC and its not really very cold down there. I was thinking of using Rotella T 15W-40 which is what I use on all my older cars and have always used in my diesel cars and tractors. What oil would you recommed. Its a good idea to T-in a manual guage right at the oil pressure switch and just leave it there. That way I always have a backup realtime reading.

 

[Don S/V ILLusion]

n the Manual -- Chapter 5 - Para 4.1 and Para 4.2
The Pressure should be between 49.78 and 64.00 psi
Check the pressure regulating spring.

Note depending on the engine panel you have, it may read in kpg (3.5 - 4.5 is normal)rather than psi.

 

[smokey73]

That was one of the things I was thinking

n the Manual -- Chapter 5 - Para 4.1 and Para 4.2
The Pressure should be between 49.78 and 64.00 psi
Check the pressure regulating spring.

Note depending on the engine panel you have, it may read in kpg rather than psi.

It reads in psig and the pressure regulating spring was what I was thinking may be the problem. It looks like its not too hard to change but it looks like you use shims to change the pressure. I'll check into ordering a new spring and shims.

Has anyone ever had to replace this and is it very difficult? It doesn't look too hard.

Dan

 

[Don S/V ILLusion]

It reads in psig and the pressure regulating spring was what I was thinking may be the problem. It looks like its not too hard to change but it looks like you use shims to change the pressure. I'll check into ordering a new spring and shims.

Has anyone ever had to replace this and is it very difficult? It doesn't look too hard.

Dan

Dan
these regulators are notorious for failing or giving bad readings and simple to replace or repair. The service manual for the engine has a good explanation.

 

[smokey73]

Source for oil pressure regulator?

Dan
these regulators are notorious for failing or giving bad readings and simple to replace or repair. The service manual for the engine has a good explanation.

Don, thanks - I have been online for about an hour trying to find a source for an oil pressure regulator - do you have any suggestions for a source? I don't have my manual with me so can't look by part number and can't seem to find it using word search.

Thanks

 

[Rick D]

First Things First...

First, get a manual gauge and check it. You may have to get a bag of adapters. I'll bet it's fine.
I have 2600 hours on my Yanmar. I am on my third oil pressure sending unit and second gauge. I don't think the first gauge was bad after all; I only replaced it out of frustration. The sending units are about $200; I think the gauge was $80+.
When I got the boat at 500 hours and five years old, the oil pressure would barely read. I had a pre-purchase engine survey and the mechanic tested the oil pressure with a manual gauge and reported it within spec's.
Later, I replaced the sending unit. No change. I then replaced the gauge. No change. I then purchased a mechanical gauge and tested it to find the pressure was fine.
So, I then went to another sending unit. It was bad out of the box.
Getting stubborn, I went back to the Yanmar distributor and bitched at him. He agreed the price was way high and sold me a universal sending unit for about $60. It was then I found out about the threads. They are unique. The universal won't fit. I can't remember what the threads are, maybe metric pipe threads. I ordered a set of adapters from egauges.com http://www.egauges.com
Well, NONE of those fit. I was however, able to get one to jam fit to use with the manual gauge temporarily to check myself.
Out of further frustration, I took the Yanmar brass fitting to an automotive wrecking yard and explained what was going on. They patiently took the part and went to the engine yard and found one sending unit that would fit. I think it was from an Isuzu truck. I tried it and it worked EXCEPT it read backwards on the gauge. I went by a VW/Audi dealer to see if perhaps a VDO unit would fit; it would not.
I should add that I bypassed the wiring harness and went right to the gauge with external wire to be sure it wasn't a problem in the harness. It wasn't.
At this point, I kind of resigned myself to just using the gauge to assure there was some pressure. After all, you still have the separate idiot light and alarm as back up.
Whenever I get bored, I am going to get another Yanmar oil sending unit brass fitting and take it to a machine shop, have them machine it to accept a universal sending unit and get a gauge to fit the panel from a different manufacturer and be done with this madness. Maybe over the winter.
At one of the boat shows, I went to the Yanmar display and explained my problem. They (off-the-record and quietly) suggested I go to a John Deere dealer with the part for much less cost. I never got around to it. Over the years, I have found this to be a common problem.
So, that's my saga. Feel better?

http://www.egauges.com/

 

[Rick D]

PS

I went to straight 40 weight oil at about 1800 hours from 20/40. Made me feel more secure. My run time is generally long.

 

[Don S/V ILLusion]

Don, thanks - I have been online for about an hour trying to find a source for an oil pressure regulator - do you have any suggestions for a source? I don't have my manual with me so can't look by part number and can't seem to find it using word search.

Thanks

Can't find a part number for the spring ("pressure regulator spring") but the shim numbers are:

.2mm thickness Part No. 121850-35210
.5mm 121850-35220
1.0mm 121850-35230

 

[Benny17441]

Does your buzzer alarm go off? If not and you do not experience any adverse symptoms whatsoever I think it would be safe to say your gauge is the problem. Check the connections to the sending unit. Do test the pressure with a mechanical gauge.

 

[Rick D]

More Info

http://www.oceannavigator.com/September-2011/Upgrading-Yanmar-oil-pressure-gauge-and-sender/

 

[smokey73]

Can't find a part number for the spring ("pressure regulator spring") but the shim numbers are:

.2mm thickness Part No. 121850-35210
.5mm 121850-35220
1.0mm 121850-35230

I found the shim numbers but couldn't seem to locate the spring number or the number for the whole unit. Any help from anyone would be appreciated.

 

[Charles Erwin]

Smokey73

Can you list the facts/symptoms - apart from the "low" dash guage reading - you have identified which suggest that you should change shims/spring in the oil pressure control valve assembly?

Has the spring sufferred changes in tension over its compressed length? If so how much tension change has occurred? Have the shims suffered a change in physical shape/size? Is the oil control piston bore scored or the piston damaged?

There is no doubt you need to verify actual oil pressure with a reliable guage - one you know is reliable - and no doubt also that you need to do this first before anything else.

Verify actual oil pressure. Then - and if necessary - verify the control piston bore is not scored and that the pistion is not damaged - before you start after changes (possibly unnecessary replacement) to the spring/shim stack components.

As has already been mentioned -- all pipe fittings on Yanmar - temperature sensor, pressure sensor, block drains, and all the rest are British Pipe Thread (BPT) not National Pipe Thread (NPT). Thus adding - or replacing stock with US sensors, bushings, etc (NPT) will not be reliable.

Charles

 

[Bill Roosa]

I'd recommend a tad more diagnosis before you go changing part and HOPING it fixes it.
If the pressure is reading low you may just have corrosion on the sender unit wire or the connections between it and the gauge. You can test the sending unit with an ohm meter. Works like a fuel guage and changes resistance with change in pressure. Specs should be available in the manual or on line.

 

[Charles Erwin]

Roosa is right.

Bear in mind the "oil control valve" is no such thing. It is actually a crude but effective device to reduce oil pressure that is otherwise too high.

That is - if oil pressure exceeds the design value - the spring/shim system moves thus to allow oil to return immediatley back to oil pan and thus reduce overpressure to the oiling system. This purpose is not to increase oil pressure.

Obviously - if the piston cannot move (the bore is scored, or the piston is damaged such that the piston "hangs up") oil pressure will reduce - but this is a very unusual event.

Charles

 

[anchorclanker]

So this guy bought a new Jag XKE in 1961. He drove it two years, and at around 16,000 miles noted a low oil pressure reading. He guessed the engine was bad and parked in a barn. It was pulled out of that barn in 1987 to be restored, as it had pretty much rotted away. We got the engine running and found it was just a bad gauge. What a waste.

Always check low readings with a known good mechanical gauge.

 

[Ray Luxford]

:neutral: Hi there. I have much the same issue. Fluctuating oil pressure, now reading zero. Engine temp rise 85C. The head is reading about 75C right across. I have very good raw water flow. I have checked the oil cooler. Is it possible the regulator on the oil filter block could have this effect? The engine, is of course almost impossible to work on. I will have to remove the inlet manifold to get to the regulator. as I will have to remove the oil filter block. As for the oil pump, I will have to lift the engine. this will not be possible until the end of the season ( charter boat!! ). Engine runs fine. Any help would be much appreciated. Cheers, Ray.