Oil & Fuel Do I need to pull the head?

Sspiderman · Dec 12, 2014

I have just purchased a 1978 YM155D that had the injectors removed 5 years ago. They don't have the injectors, seals or hold downs, but I think I can order all the parts I need from Hoye. The engine cranks on battery power like a champ & seems to have decent compression, etc. My concern is that there looks to be crud (spiderwebs, dust, etc) in the injector holes. Is there a way to clean the intake out without removing the head? Even if I remove the head am I going to be able to clean that area out without tearing the head right down and hot tanking it or something?

pmsmechanic · Dec 12, 2014

I'm going to make some assumptions here because what you write is not entirely clear. By cranking the engine over you have already sucked some junk into the combustion chamber so if you add a bit more I would say it's not a big deal. To clean out the injector holes they need to be wire brushed with a round wire brush. I haven't checked but you should be able to find these at Acklands or a similar store. For sure your local diesel shop should be able to loan you theirs or supply one for you. Round wire brushes come in different sizes so measure your holes before you go shopping.

Since you ask about cleaning the intake out I'm going to assume that the intake manifold was removed. This I would have done before turning the motor over but it's to late now. I would make sure the intake valve is closed for the intake port you are working in. Then blow air into it while brushing with a small wire brush as much as you can. If you can't reach everything then get some brake clean and wash the whole port down thoroughly while blowing air. Some brake clean might leak through the valve but not enough to worry about.

Clean the intake ports first and then start on the injector holes. Next make sure the intake valve is open but not the exhaust valve for the injector hole you want to clean. I would stuff a rag into the intake port along with the air blower. As you are wire brushing the injector hole blow air into the corresponding combustion chamber. This will blow the crap out the injector hole while you are cleaning it. All the rust if present and junk needs to be removed from the injector hole before you install new injectors. If you have to force them in something is wrong. Make sure the old copper washer at the bottom of the injector hole gets removed. Test fit the injector and then before you bolt it in give it and the hole a light coating of never seize. That will make the next mechanic who removes the injectors happy. Before you hook up the injection lines I would at least make sure diesel is coming out of each line while you crank the engine over. At least then any loose junk in the line will be flushed out.

winston1 · Dec 12, 2014

You have an upper and bottom chamber under the injector. Assuming they are still down in there here is a picture of what the bottom chamber looks like. Yanmar Tractor Parts INJECTOR CHAMBER - BOTTOM *OUT OF STOCK * This is not yours but yours will look similiar. Since you have already spun the engine I would blow in there good with air, put the injectors in and see what happens. Do you have any history of what was going on with it when the injectors were pulled? If you had a gauge now would be a good time to check compression. Yanmar Tractor Parts: Search

clemsonfor · Dec 12, 2014

well if your cranking it all that crud is bouncing around inthe cyl. If you did it with a tester in it most likely blew it out exhaust if no injector it prolly blew it out the hole. But as easy as it is i would pull the head.

California · Dec 12, 2014

There has to be a reason why the prior owner pulled the injectors then abandoned the project. It's simple to pull the head from a 2 cylinder Yanmar, I would just pull the head and take it in to a diesel shop for inspection and rebuild as necessary.

I expect this will avoid much aggravation between now and the day you put the tractor back in use.

winston1 · Dec 12, 2014

How are you going to know the condition of the rings without either checking compression or cranking? Head gaskets are also expensive.

normde2001 · Dec 13, 2014

" seems to have decent compression"

What are you basing that on?

clemsonfor · Dec 15, 2014

yea but buying a head gasket is cheap insurance when you do pull it. I would hate to see him put the injectors back in and then just have to pull it all back down again to take to a shop that does deisel heads, then still have to put a gasket in it.

clemsonfor · Dec 15, 2014

normde2001 said:
" seems to have decent compression"

What are you basing that on?

The old finger over the hole trick? haha!!!

Sspiderman · Dec 23, 2014

Based the compression by the amount of air movement through the engine and the force it was exploding out with.

This is my first diesel but not my first rodeo, I have rebuilt several engines, from 1 lung 2 stroke dirt bikes to big block fords. I rarely pay mechanics (except for the computer crap), but I always do plenty of research (except when I get excited and crank the engine to soon... DOH!), before tearing into a project so I'm really comfortable when I do dive in.

I appreciate the comments and suggestions regarding my tractor. After I recover from hernia surgery, I will include the top end gaskets with my injector order and pull the head, as that seems like the prudent move. The previous owner (my brother-in-law) didn't pull the injectors, his ex-girlfriends dumb assed brother did & nobody knows why, so better to spend a little extra than cause more damage.

Parts in Canada for this model seem to be hard to come by, they want $600 plus shipping for the 2 injectors (no hold downs) vs $81/ea from Hoye. Fortunately, my father lives in Wa State, so I can ship parts to him and pick them up during visits.

Question for Winston1, how do I check compression on a diesel?