VP D1-30 low oil pressure at idle

[mfair]

My oil pressure buzzer activates when i reduce throttle to idle on a warm engine.
There is no alarm when idling at start up or when running at higher rpms. It only sounds when coming into the harbor after running under power for a while.

it is a D 1-30 that started at about 300 hrs and now has 400 hrs. i have used perkins and volvo filters and used several different oil weights with no effect.


any ideas?

thanks,
mike

[Lepke]

Your low pressure is probably bearing or oil pump wear. Because the oil pressure fails after it's hot and various weights of oil have been tried, about the only thing you can do is remove and inspect the oil pump for wear. Also check bearing clearances. None of this is going to be easy.
If you continue to operate the engine with low oil pressure, either you will need major repair or throw a rod and damage the crank and block beyond repair. It can also lead to cam and timing gear failure.
You could try a single weight heavy oil. Maybe 50 weight. It's not the filters. It's because the hot, thin oil has an easier escape thru a bigger bearing clearance or wear inside the pump. At speed, the oil pump puts out more oil at higher pressure.
There is a remote 3rd posibility, the oil pressure valve spring (usually in the oil pump) is weak and when hot allows the valve to remain open slightly.
You're probably going to have to remove the pan. You can buy Plasti-gauge at auto parts stores. Thin plastic that is placed in the bearings before assembly and torquing. When bearing cap is tightened, plastic spreads and with the supplied chart, clearances can be determined w/o mic'ing. Probably the bearing shells will show major wear.
My guess is someone ran the engine out of oil in it's past.
If you're lucky, replacing the oil pump or oil pump + main and rod bearings, you'll restore enough pressure.

[captjcook]

Starting to like this guy Lepke...lots of sound answers. One however may have been overlooked. Since the engine only has 400 hrs...what if it is the sender or a bad ground?


Sent from my iPad using Cruisers Sailing Forum

[DougR]

The problem you are having is not entirely unheard of on this engine. Normally it can be solved by a good grade of 15/40 or 20/50 oil like Rotella T, or sometimes just a few moments of higher RPM without load to cool down the oil. It could, of course, be something serious as described by Lepke. In any event there are a few things that you can check before diving into the engine.

First thing is to actually check the oil pressure and see what you have. The oil pressure specification for the D1-30 at idle, hot engine, is "greater than 7 psi".

To check this, remove the oil pressure switch on the Stb. side of the engine and install an accurate gauge. The gauge shouldn't have a range greater than maybe 20 psi to ensure that you get an accurate reading. Replicate the conditions that cause the alarm and see what pressure you get. If the pressure is around 7 psi, you should check the alarm switch. The switch is normally open when oil pressure is present and should close at .5 bar (7.25psi) plus/minus .15 bar on falling pressure. That means it should make contact between 5 psi and 9.4 psi on its way down. If you check it on rising pressure it won't be as accurate.
Early on with this engine the switch value was too high and many false alarms occurred until the switch value was lowered. If you get a replacement switch, check it out before installing.

If the oil pressure is actually low, the next thing to check is the oil pressure relief valve. Pressure relief valves are designed to protect the oil pump and oil system from too much pressure, so you can wouldn't think they would cause a low pressure problem, but sometimes the spring or plunger in the valve can get hung up and allow a small leak back into the crankcase. This shows up as low pressure when the engine oil is hot and the engine is idling. Luckily, on this engine the relief valve can be accessed from outside the engine. It is located just adjacent to where the oil switch is located on the Stb. side of the block, and it has a hex head that looks like a large bolt screwed into the block. Remove the valve and check for dirt, debris, etc holding the valve open a little bit. There will be a bit of oil leak out when you remove the relief valve.

If everything looks OK with the relief valve, the oil pump is next. The oil pump is located behind the front timing case on the front end of the engine block. To get to it you have to remove the front crankshaft pulley, the seawater pump and then the timing case itself. Before the timing case can be pulled away from the block, the injection pump must be loosened up a bit so that the governor linkage can be disconnected from the inj. pump. The oil pump is a trachoidal type pump with an inner and outer rotor, and a shimmed front plate. I doubt there is enough wear in the rotors to cause any problem at these low hours, but sometimes the front cover isn't shimmed tight enough and needs to be reshimmed to recover some lost pressure. This is easily done with the available shims, and the clearance should be set to the minimum spec.

The last thing that might be an issue is the O ring fitted to the oil pump suction tube, where the tube enters the engine block. Any damage to this O ring can cause pressure issues. Access to the O ring entails dropping the oil pan, and if you are that far in you could also check the rod bearings for excessive wear, although I think you might hear it knocking if this was a problem.

Some of these measures might require the services of a trained technician, but if you want to get an idea of what is involved, Google " D1-30 service manual" and you will find a couple of on-line sites that offer the manual for free. I think the Manta owners site is one, and also the J109 site. (j109.org)

Hope this helps some....
DougR

[a64pilot]

Always, always, verify the gauge first.
I had a customer that literally spent thousands chasing a high oil temp problem on a Pratt & Whitney T34 turbine, I showed up to help him troubleshoot and turned on the battery switch and looked and saw the oil temp was 50C on a cold engine.
Yep, nothing wrong except the temp gauge.
Years ago my Fathers Ford Diesel truck's oil psi light would come on when hot and at idle, the tiny little hole in the transducer was partially clogged, picked out the hole with a pin, problem solved.
Temporarily plumb in a cheap oil pressure gauge you get from a an autoparts store and verify pressure first, but it does sound like excessive clearance, but 400 hours?

[mfair]

Excellent responses. I will not be able to test this until i launch in May but
PLAN A looks like:
1. change to oil recommended above, i haven't tried 20/50.
2. install a good oil pressure gauge (something I have wanted to do).
3. clean out the pressure relief valve.

Regroup.

PLAN B looks daunting!

Thanks all,
Mike

Buzzards Bay, MA
finnyacht 351

[libera]

Hi Mike,
could you find the problem?
I have the same engine, exact the same problem.
thanks,
Manfred