Generator oil pressure shutdown. Plenty of oil but thin and smells of diesel.

Nick_H

Nick_H

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www.ybw-boatsforsale.com
Generator shut down over the weekend showing an oil pressure fault. Plenty of oil in it, but I noticed it seems very thin and when hot will run down the dipstick leaving some of it almost clean metal. The oil seems to smell faintly of diesel.

Once cool it restarted and ran fine on low load for 20 mins before I switched it off.

It's a 2004 with about 2500 hours. It has done a lot of hours since the last service, maybe 3-400.

Does it just need an oil and filter change, or does it sound like something more serious?
 
100 hrs 200 tops for geny oil change .Perhaps more frequent if 2500 hours up .
What does the manual say ?
My yanmar powered Mase suggest 100 hrs or annual which ever comes first .
I use 10 /40 w same as the main engines .
I noticed on a few super yacht adds as well as fuel tank size , water tank , + water maker capacity ,
They also refer to geny oil tank -like 57 gallons as if they store oil to change regularly as running 2-3 genys almost full time you soon rack up 200 hrs -therefore cruise about with 57 gallons of 10/40 w
 
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Portofino said:
100 hrs 200 tops for geny oil change .Perhaps more frequent if 2500 hours up .
What does the manual say ?
My yanmar powered Mase suggest 100 hrs or annual which ever comes first .
I use 10 /40 w same as the main engines .
I noticed on a few super yacht adds as well as fuel tank size , water tank , + water maker capacity ,
They also refer to geny oil tank -like 57 gallons as if they store oil to change regularly as running 2-3 genys almost full time you soon rack up 200 hrs -therefore cruise about with 57 gallons of 10/40 w
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Yeah, I did lose track of how many hours I was putting on my genny, and was surprised to see it had reached such a number since the last service, but as you say big yachts run the genny day and night, do they really have to change the oil every 4-8 days?

I'm keen to know if the thin dieselly oil is a sign of engine damage, or whether an oil change may be all that's needed.
 
Change the oil, see how it goes.
There are very few places that diesel can get into the oil, had a similar thing on a tractor (note that the oil level went up!), turned out to be a small split in the fuel lift pump diaphragm. Its more likely that since everything on a diesel engine smells of diesel, its not fuel in the oil.
 
Nick, afaik the book change interval on your model is 250hrs (it's not a constant onan value - it's 350 hrs on mine, phew) but 3-400 aint a crime and won't cause big issues

Is the oil level high? If it is, you probably have a diesel leak. Perhaps a gasket failure near the oil pump or something (along the lines Dougal also guesses). It is v unlikely to be proper "engine damage". You might see the likely leak culprit from the exploded parts diagram that comes with the genes (online too I guess) and see what components to buy

The leak might so marginal that if you just change the oil you'll be fine - keep an eye on it of course.

Diesel in the oil would also explain the low pressure warning light. With a bit of wear in the oil pump (probably a gear pump) then too-thin oil will certainly lead to a pressure reduction

I'd just change the oil and monitor it a bit. ARE might chime in too
 
Never been that hands on with Kubota G drive motors, however plenty of time with high hour Yanmar G drives for MOD and common failure is the Denso lift pump which fails internally and mixes fuel with the lube oil as it mounts on the side of oil lubricated injection pump.

Shutdown should prevent lasting damage.
 
Thanks for all replies, it's nice to hear that I'm unlikely to have done serious damage to the engine. I think the oil level was high, but I'm not at boat now to confirm it. I'll ask engineer to check/service/replace the lift pump as well as a full service.
 
Forty_Two said:
Worth getting the oil tested when you change it, will soon show any diesel content & give you a reference for next time.
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Absolutely no need.........Life is far more simple

Smell it, if in any doubt put small sample on some sheets of bog roll and look for the halo around the sample
 
Nick_H said:
Generator shut down over the weekend showing an oil pressure fault. Plenty of oil in it, but I noticed it seems very thin and when hot will run down the dipstick leaving some of it almost clean metal. The oil seems to smell faintly of diesel.

Once cool it restarted and ran fine on low load for 20 mins before I switched it off.

It's a 2004 with about 2500 hours. It has done a lot of hours since the last service, maybe 3-400.

Does it just need an oil and filter change, or does it sound like something more serious?
Click to expand...

Hi Nick,

I am not sure what has happened to my old loggin (ARE) but I have had to re-register.

The first thing I would do is change to engine oil to ensure it is the correct grade, I have seen a few instances where an engineer puts the same engine oil in the generator as the propulsion engines. Onan's should be filled with 15 W 40 mineral based oil, no synthetics or semi synthetics.

There is no mechanical lift pump fitted to your generator, an electric lift pump is bolted to the side of the block. So it is not possible for you to leak fuel into the oil from the lift pump.

If you notice the oil level rising the only place you can leak fuel into the oil is via the injection pump body. The injection pump is a cartridge type bolted into the side of the block and a small fuel camshaft operates the pump plunges directly. It is possible for fuel to leak around these pump plungers, however it is rare on such a low engine hours unit.

Have you every had any water in fuel issues before? As with any injection pump water ingress can cause premature failure.

I would suggest if you have any doubt over the pump to remove it and have it overhauled.

Regards Anthony
 
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bunglebear said:
Hi Nick,

The first thing I would do is change to engine oil to ensure it is the correct grade, I have seen a few instances where an engineer puts the same engine oil in the generator as the propulsion engines. Onan's should be filled with 15 W 40 mineral based oil, no synthetics or semi synthetics.

There is no mechanical lift pump fitted to your generator, an electric lift pump is bolted to the side of the block. So it is not possible for you to leak fuel into the oil from the lift pump.

If you notice the oil level rising the only place you can leak fuel into the oil is via the injection pump body. The injection pump is a cartridge type bolted into the side of the block and a small fuel camshaft operates the pump plunges directly. It is possible for fuel to leak around these pump plungers, however it is rare on such a low engine hours unit.

Have you every had any water in fuel issues before? As with any injection pump water ingress can cause premature failure.

I would suggest if you have any doubt over the pump to remove it and have it overhauled.

Regards Anthony
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The oil was a quality 15W40 mineral (Shell Rimula), which is actually the same as the engines.

Thanks for the info about the pump. The general opinion is that the fuel in SoF is high quality, and I've never seen any water in the separator bowl, however if I confirm diesel in the oil I'll have the pump overhauled.
 
Keep a small sample put a few drips of equal size of new and used oil on a flat piece of something non pours and tilt it up, see if one oil runs faster down it than the other. If it does one is thinned out with fuel.
 
Nick_H said:
The oil was a quality 15W40 mineral (Shell Rimula), which is actually the same as the engines.

Thanks for the info about the pump. The general opinion is that the fuel in SoF is high quality, and I've never seen any water in the separator bowl, however if I confirm diesel in the oil I'll have the pump overhauled.
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Hi Nick,

You might want to consider removing the pump and bringing it back to the UK for overhaul if necessary, I expect it to be considerably cheaper.

PM me if you want the details of the pump specialist we use.

Regards Anthony
 
ARE said:
Hi Nick,

You might want to consider removing the pump and bringing it back to the UK for overhaul if necessary, I expect it to be considerably cheaper.

PM me if you want the details of the pump specialist we use.

Regards Anthony
Click to expand...

Anthony, yes please PM me the details.

Is removing the pump a DIY job? I have an engineer going from the UK to carry out all servicing probably end of Nov, so if I could remove it, bring it home, and have it overhauled beforehand, then he could re-fit and test it.
 
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