Yanmar Lift Pump

[delmarrey]

Charlie,
Here's a couple pictures that might be of interest. I don't know which motor you have, but these are from a 3JH/4JH.
I suspect if there are leaking pump piston seals leaking, the pressure can force the fuel back down the lube line and mixing with the oil.

.

[Charlie]

Del thanks
U the Man!
that is what I need to study. I have the 4jh4E. I should have brought the parts manual home with me.

[delmarrey]

Here's a link to the 4JH. Goto page 38. >>> http://marinegenerators.us/kohler/lit/TP5229.PDF

Also page 42. I've heard the the diaphragm can rupture and allow fuel into the crankcase.

[Charlie]

Del thanks for the link this helps a lot. I am looking at page 42 and wonder if I installed the gasket #2. I don't remember doing that but I do remember a gasket that attached in between the lift pump and the injection pump. There were two different gasket types. One that was round when looked at in section view and another that was square in section. If I didn't install the gasket #2 it looks like that might allow the leak that is occurring.

[delmarrey]

The #2 gasket looks like it could be an O-ring, but primarily to keep oil from leaking onto the motor/pump IMO.

BTW I've heard of the diaphragm going bad fairly often. I think I would look at that first. And if it's the problem carry a spare. I think I'll be doing so for my 3JH.

[Charlie]

Originally Posted by delmarrey

The #2 gasket looks like it could be an O-ring, but primarily to keep oil from leaking onto the motor/pump IMO.

BTW I've heard of the diaphragm going bad fairly often. I think I would look at that first. And if it's the problem carry a spare. I think I'll be doing so for my 3JH.

I agree with the spare. Also it is nice to have an electric fuel pump plumbed in. I have this. When I put the electric pump on I disconnect the lift pump completely and run the electric pump up to the secondary fuel filter. This does resolve the problem but isn't how the engine is supposed to work. I have two lift pumps now. I am going to test them both to see if the diaphragm is good on either one of them.

[delmarrey]

Check out this link too. Yanmar dsl - lift pump failure? - SailboatOwners.com

I have an elect pump too but just for bleeding the system.

.

[Charlie]

In speaking with another friend of mine he says that on naval ships when he had problems with the fuel oil contaminating the lubricating oil most often it was an injector that was not atomizing the fuel and this was causing the fuel oil to be forced back into the lubricating oil. Would anyone care to comment on this?

[Charlie]

Bump Anyone?

[cheoah]

Are you using your engine or has boat been sitting? How does your engine run? I think it might just be bad luck on two pumps but doesn't hurt to dig deeper. IIRC there was an article in Ocean NAvigator a couple months ago on rebuilding them.

[Chief Engineer]

Originally Posted by Charlie

In speaking with another friend of mine he says that on naval ships when he had problems with the fuel oil contaminating the lubricating oil most often it was an injector that was not atomizing the fuel and this was causing the fuel oil to be forced back into the lubricating oil. Would anyone care to comment on this?

Yes...that can happen....the cylinders get washed with fuel and the fuel leaks past the rings....pretty soon you have a lot of crankcase pressure....I doubt if he is to that point yet as he hasn't reported any smoking

[bgallinger]

I've been told a simple test for these Yanmar lift pumps. Attach a hose 3 feet long, hold it vertically then crank to see if fuel is pumped up the hose. If fuel doesn't make it, you may have a faulty pump. I have seen a retrofit from Torreson for these pumps to allow better unrestricted flow.

[Charlie]

Originally Posted by cheoah

Are you using your engine or has boat been sitting? How does your engine run? I think it might just be bad luck on two pumps but doesn't hurt to dig deeper. IIRC there was an article in Ocean NAvigator a couple months ago on rebuilding them.

I don't use the engine very much. Mostly to get in and out of the dock. It has been sitting for three months b/c I was out of the country.

Originally Posted by Chief Engineer

Yes...that can happen....the cylinders get washed with fuel and the fuel leaks past the rings....pretty soon you have a lot of crankcase pressure....I doubt if he is to that point yet as he hasn't reported any smoking

I did get smoking when I was in Mexico. That is what led me to find this problem. I thought I had fixed the problem by replacing the lift pump but now I see that the problem is still there.

Plan of attack: 1) run a test on the diaphragm as suggested in the manual. 2) I 'm not sure if this is the proper order. Remove injectors and have them serviced. 3) permanently bypass the lift pump with an electric pump. Does this make sense?

[Chief Engineer]

You are making way too much work for yourself.

If the engine is making oil...it is most likey the diaphragm is shot.

Don't waste your time testing....replace it and get a rebuild kit...put that pump away as a spare

I don't know why you want to futz with the injectors.

If you run the engine for short intervals...that will cause the injectors to foul. Diesels need to be worked......light use is not good for them