Yanmar 2GM20 Shoots Oil Out Dipstick Hole

[Sonosailor]

The oil from the crankcase of our starboard engine is being shot out of the dipstick hole into the bilge. Our 2GM20 Yanmar used to do it once or twice a season, but this year it went first to 6 weeks, then 4 weeks and now it seems weekly. We never notice any trouble, then bang, a big mess and the dipstick is loose. I mentioned it to a mechanic at Fred Marine in Pointe-A-Pitre, and he said it was most likely a bad diaphragm in our fuel lift pump. The lift pump runs off a cam inside the engine block, and if the diaphragm goes, fuel can leak into the crankcase until it is a problem. He sold me a "rebuilt" pump for 50 euros, and, after my guests were gone and we were in Antigua, I put it on and started the engine. Worked like a dream, so we started to lift anchor when the engine raced out of control. By the time I had gone down, dug down to the engine, and stuck my hand over the intake, there was a big mess coming out of the exhaust. I checked the dipstick (I had also wedged it a little tighter) and when I pulled it out a half litre of oily fuel poured out of it. The fuel had got so high in the crankcase that it travelled through the crankcase breather, around the tube to the air intake, and the engine took off!

I brought the boat into Jolly Harbour, Antigua, and started up a relationship with the mechanic: Carl Mitchel. Nice guy, really. I took off the injectors and he tested them as well as the two fuel lift pumps. My old lift pump worked while the "rebuilt" one was truly faulty, and had nearly destroyed my engine and/or boat! Carl also believes the problem of disgorging oil out of the crankcase is a matter of fuel getting its way in, but believes it can only be via the high-pressure injection pumps. Makes sense, as that is the only other location that fuel enters the exterior of the engine, with all fuel piping being exterior. As few people work with these pumps, he said he'd only take my pumps out if he had another to slide in - he is looking, while I keep sailing around Antigua. The engine is available, but I seldom use it.

There is a carbon buildup that only shows itself when we run it around 2500 rpm. Otherwise the engine runs like a dream and Carl does not suspect any problems with piston, cylinder, rings.

Any one with experience or ideas, or opinions on this? It may not be an issue of fuel in the oil, as I really couldn't tell from the mess in the bilge each time, but it makes the most sense.

[Sailmonkey]

If you're making oil, and it's not milky......it's fuel.

[gjordan]

The first mechanic was correct in saying that fuel in your motor oil is usually from a bad lift pump. The key word is usually! If your present mechanic thinks the rings are OK then it is probably the front seal on the injection pump, but before you spend big bucks on a new or rebuilt pump, you might want to have him pull the injectors again and do a compression test ( preferably a leak down type) just to make sure you are chasing the right thing. A diesel can run surprisingly well with worn rings although they get hard to start, but sometimes enough fuel can get past worn or damaged rings to cause your problem. Do the less expensive tests before you commit to what will probably be over a thousand dollars for a rebuilt pump. I hope this helps._____Grant.

[Charlie]

I am having the same problem but not as severe. Here is my solution to track down the problem. I would appreciate any comments on my plan. To set the table I have a different engine Yanmar 4JH4E. There are three ways that engine oil and diesel can mix 1) Injectors dripping thru the rings, 2) Injection pump putting oil in crankcase (not sure of this one), and 3) Lift pump. This is the most common as gathered from info on the internet (take it for what it is worth)

Test 1) change out lift pump. I did this and it didn't resolve the problem. Alternate test is to remove the lift pump from the picture. Use fuel lines to recirculate the lift pump and plumb in an electric pump as a lift pump. This did resolve the problem.

I am in process of inspecting the two lift pumps I own.

I was told by a licensed diesel engineer that there are two paths to follow now. 1) the second pump may be bad too and 2) the lobe that runs the lift pump may be bad and causing the problem. I don't know how to check for the second problem.

Good luck with your problem I hope my info helps.

[gjordan]

Charlie, it is unlikely that a bad cam lobe would cause a diaphragm in the lift pump to allow fuel into the sump. Cam lobes that go bad generally go soft and give you less and less lift until you dont get any fuel pressure out of the pump. It is more likely that you have 2 faulty pumps if using the electric pump solved the problem. Pin hole leaks are very hard to detect in a diaphragm even with good light and a magnifying glass. I have had 2 different Perkins that had so much trouble with lift pumps that I switched to electric and had no more problems. Hope this helps.____Grant.

[bluetriguy]

I agree that it might be a lift pump. BUT - you really need a compression test done but have it done with the dipstick OUT. Have the mechanic place a small rubber balloon over that little piece of dipstick tubing and put a rubber band around it.

If the balloon starts to fill up in 'pulses' you have at least one ring problem. What can happen is that when the crankcase is cold the oil is pretty sticky. As the engine runs the bad ring injects a little pressure into the crankcase. As the engine warms up, the oil at the bottom of the dipstick tube gets thinner.

At some point the pressure in the crankcase is more than is what is needed to push the dipstick out (actually it's not pushing the dipstick, it's the cap on the top of the dipstick) like a cork in a kids pop gun.

Your crankcase must be glued together or this would simply cause a bad leak in the bilge.

[travler37]

Every one posted going for fuel.why?Cause the meck had a lift pump for sale?

Wipe your finger in the tube and SMELL...does it smell like fuel.....i bet not.
From what you describe.happened once......happened again a little lator.....Piston rings...do a compression test..wet and dry......
if you do not know how to do this yourself ask around for a meck that has a good rep and go talk to him......
Tell him you want to do a comp test and want to be taught how..AND NEED TO BUY THE TOOLS TO DO IT IN THE FUTURE..from him..
you might be surprized
Mark

[delmarrey]

One can test the lift pump by forcing fuel back up the exit tube of the pump. If it leaks out the little hole in the cam follower then it has a bad diaphragm. But do be careful not to exceed 10 psi the pumps are only rated at 7 psi.


.

[LeaseOnLife]

How about not using the built-in lift pump?

Depending on location and accessibility to parts, it might be easy to get and plumb a little electric fuel pump from an auto-store.

Or, make yourself a little day-tank, and let gravity do the job. Same idea, not to use the built in lift pump. delmarrey says 7PSI, this would be 0.5 bar. With diesel being lighter than water, I would say a daytank 2-3 feet higher than the injection pump of the engine should do the job.

Then see if the problem still happens...

[Charlie]

Originally Posted by gjordan

Charlie, it is unlikely that a bad cam lobe would cause a diaphragm in the lift pump to allow fuel into the sump. Cam lobes that go bad generally go soft and give you less and less lift until you dont get any fuel pressure out of the pump. It is more likely that you have 2 faulty pumps if using the electric pump solved the problem. Pin hole leaks are very hard to detect in a diaphragm even with good light and a magnifying glass. I have had 2 different Perkins that had so much trouble with lift pumps that I switched to electric and had no more problems. Hope this helps.____Grant.

After I posted that I studied the cam lobe and believe that it would be near impossible for that to cause a problem. Thanks for the heads up though.

Originally Posted by travler37

Every one posted going for fuel.why?Cause the meck had a lift pump for sale?

Wipe your finger in the tube and SMELL...does it smell like fuel.....i bet not.
From what you describe.happened once......happened again a little lator.....Piston rings...do a compression test..wet and dry......
if you do not know how to do this yourself ask around for a meck that has a good rep and go talk to him......
Tell him you want to do a comp test and want to be taught how..AND NEED TO BUY THE TOOLS TO DO IT IN THE FUTURE..from him..
you might be surprized
Mark

It is not that easy to identify diesel in lubricating oil. I couldn't figure out for sure that I had diesel in my lube oil till I compared how the two oils ran down a piece of glass. The viscocity was very different.

Originally Posted by delmarrey

One can test the lift pump by forcing fuel back up the exit tube of the pump. If it leaks out the little hole in the cam follower then it has a bad diaphragm. But do be careful not to exceed 10 psi the pumps are only rated at 7 psi.


.

Thanks Del that is a great help. I will test both of my lift pumps that way and see how they react.

[travler37]

If you have a good sniffer its not to hard,
This is where you laugh.......hopefully.
Try pulling a pint of oil out and let it sit for a day.Fuel and oil will seperate.Still leaening towards a bad ring.Comp. teast will tell.

if that is the case something to try that has worked.Fill cylander with PB blastor.Leaving injectors out turn over by hand every when you remember to for a few days.Re-fill as needed.Leave rest of injectores out.
after a few days of this hit the startor to clear cylender of most of blastor.Reinstall injectors and bleed/start.Run for awile and see if you still have a blow-by problem.If not change oil and cross fingers.Gave me another 300,000 miles on a road diesel.
My Thoughts
Mark
PS.Please update us on this....

[gjordan]

The PB blaster is a good idea. Turn the engine slowly until you decide to clear it with the starter. Then make sure you have an old towel or lots of rags over the injector holes because fuel will spray like hell. I wonder how I learned that lesson?____Grant.

[Cheechako]

A bad injector can pass raw fuel surprisingly fast. I had this happen a couple of years ago. I was making oil fast. Compression tested fine, it was a 4 cyl engine. Crack off the injectors one at a time with the engine running. If one doesnt slow the engine down, that's your bad cylinder. If an injector is washing the xylinder, you need to fix it before it destroys the cylinder wall.
Could be the injector. That series of engines has some trouble with cracked pistons also. I got ripped off in Antigua with a head rebuild which didnt fix the problem. "Butch" in St Thomas fixed it right and well at a good price. (3gm30)

[gjordan]

Sonosailor, I hope you keep us posted about your successes (or failures) as this is one of those educational threads for all of us. ____Grant.

[boden36]

I may have missed it above, but have you checked your engine breather? A buildup of crankcase pressure through inevitable small amounts of blowby will exit through the dipstick tube if there is nowhere else to go.
Regards,
Richard.