Bad Luck Good Luck NO LUCK

[SEADANCE]

About 3 weeks ago we notice a substantial loss of power under load from our yanmar 2qm15 engine. After reading and researching we decided to check all filters and inspect the mixing elbow. Upon removal we found that the mixing elbow was in poor shape and would not be seperated easily from the flange. We replaced the flange elbow assembly and exhaust hose to the muffler. While in the process we also decided to take a close look at the fuel filters. The primary and secondary filters were replaced. When we started the engine died because of incorrect bleeding procedures. After several tries we were successful and the engine started and ran better than it ever had. There was no more white, brown or black smoke and it seemed to idle fine for about 6 minutes. However, while inspecting the engine compartment, exhaust was felt escaping from around one of the bolts that holds the high water temp sending unit and zinc to the aft of the engine block. While running my hand under the lip along the head gasket line I also had lube oil leaking. The next day we cleaned the area well and started the engine to try and locate the exact location of the leak. The engine ran for about 30 seconds and died again. Again the low side was bled and there was an unusual amount of air. The lift pump lever was actuated several times by hand before fuel exited the bleed screw. However when we tried to bleed the high side we could not get fuel from the injector pump to the injectors. Our initial fear is the injector pump is shot, since after checking the low side several times after the engine died there was steady fuel and pressure. Any thoughts or suggestions?

 

[Ed Schenck]

Bleeding difficulty.

From experience with a 2QM20 I can only tell you that it is really difficult to bleed using the lift pump. A Yanmar mechanic will bring his own pump. But you can make one to bleed and prove or disprove a failing fuel pump.

Buy or borrow a small(two or three gallon) outboard motor fuel tank, the one with the squeeze bulb on the hose. Cut off the outboard attachment end of the hose(the hose is cheap to replace). Clamp that hose end to the input side of your primary filter. Naturally the tank has a gallon or so of diesel fuel. With pressure built up with the squeeze bulb you should easily get the air out all the way to the injectors.

I think you will find the fuel pump is not a problem. Then you will have to deal with what could be a blown head gasket(the oil leak under the ridge). Hopefully that was just a loose bolt.

 

[John Nantz]

The Devil is in the Details (air leak issue)

One downside with diesels is air leaks. Just the smallest air leak will raise havoc with the fuel system.

After the engine cools down and sits for a while it seems that it can suck air much easier though even the smallest of air leaks.

The manual says you should replace the copper washers. There are copper washers under the bleed screws on the engine fuel filter and on the banjo fittings. Buy a bunch of 'em and don't be stingy useing them.

One trick I've used to squash an airleak is to put a small amount of Permatex on the pipe thread (fittings like on the fuel tank or filters, filter bleed screws, etc.). One thread-worth should do it. No need to gob it on and less is more.

If the engine can run at all, a good bleed location is at the injector. Put an adsorbing material under the banjo fitting and crack the nut momentarily while the engine is running. The engine will run rough for the moment but if it seemes like it's going to die then tighten. Then repeat. Then go to the next injector. The engine should run smoothly after its done.

If the dying problems continue, or it runs rough again after a while, there's an airleak somewhere and you've got to find it.

The lack of power and oil leak are other issues.

 

[s sauer]

Permatex?

I would caution you NOT to use any sealant on fuel system connections, just replace the copper washers and bleed screw washers. If any sealant finds its way downstream into the high pressure pump you will be faced with an expensive re-build.

 

[SEADANCE]

Engine trouble

Thank you all for the info so far..
already have replaced washers. Could not get copper..Yanmar replacement part washers are now nylon and seem to work. Fittings are also tight, but we are going to try and push fuel as suggested again this evening. Will let you know how it goes.

Please keep the suggestions coming.

 

[filthy liberal scum]

Seadance; there's some advise here thats overblown

I have had this same engine in my boat for 18 years and there's little difficulty bleeding the system.
first; remember that you have a compression release, use it. you also have a hand crank, use it too.
second; the manual lever on the primary fuel pump is actuated by the camshaft. hand crank the engine to where you literally can feel that you are getting the full stroke out of the lever.
third open the engine throttle lever to full open. next, open bleed screw on the secondary fuel filter and start hand cranking until nothing but fuel comes out then close it. next move on to the discharge connections at the injector pump. after these have been bled then move on to the connections at the injectors, this bleeds the air out of the lines.
if it doesn't start right up then you may have to go back and possibly do the sequence again. although i must say that I've never had to do the sequence twice.
I can't emphasise enough that you have to go through the entire sequence. if you don't then you won't get all the air out of the system.

if by chance you get a lot of air and have to do the sequence twice i would look for an air leak in the suction side of the pump. this is the only place you can pull air into the system.

now on to your oil problem. oil leak is the valve cover gasket. I've had to replace mine twice. has been several years though because yanmar changed the design of the gasket from the original. over time the orig gasket/"O" ring drys out and it will slightly leak. don't even think about resealing it, it won't work. BTDT
you should not have any exhaust leak around the fitting that hold the zinc and the temp alarm sending unit. there is only water on the inside of that fitting.
if in fact you are feeling exhaust gases then check you riser very carefully for a leak in the side of it. I had a pin hole in mine but i was able to weld it shut. Not a fun project i might add.

If you have any problems e-mail me through the site and I'll give you my phone# and we can discuss it. I have the complete engine service manual. I did a complete rebuild of my engine using this manual.

 

[John Nantz]

Engine Filter Bleedscrew

Good step-by-step comments Jim. The one place where one can normally get a lot of air out is at the engine filter by cracking the bleed screw at the top of the filter. The one thing to be very cautious about is stripping the threads when tightning the screw. The potmetal is pretty soft. Air leaks here are likely before it totally fails and the threads strip.

Didn't know they switched over to plastic washers - I still have a bunch of copper ones.

re the Permatex thing - if you're between the engine filter and the fuel tank, and that is where a lot of the screw thread connections are, it shouldn't be a big problem as the engine filters should catch anything that is a problem. However, I still woudn't over-do it.

If everything else seems to fail, another spot to check is the fuel hose. It could have a pinhole leak. This would probably be at the point where it goes on the metal barb fitting or, perhaps, at the hose clamp. If the hose is the Coast Guard approved type it would be less likely (because they are really robust) but I've seen automotive fuel hoses used and there is a greater chance for this.

 

[SEADANCE]

The plot thickens

Thank you again for all the advice. This evening we went to the boat again. When we checked the bleed screw it was fine. When we finally got the banjo bolt loose on the injector pump (fully removed) and operated the lift pump nothing happened. Remembering that we accidently loosened the delivery valve spring holder (or injector pump check valve) then tightened it, we broke the seal by turning 1/8 of an inch back and we were getting fuel through again when actuating the lift pump manually) We then moved on as described and success for about 10 minutes. When we idled down the engine died again and we noticed again the injector pump was not working until it was backed off again and there was again a large amount of air on the low side. So in keeping with the definition of maddness we decided to go through the process again expecting a different result, and again it worked. However, just for fun, we cracked the bolt on the injector line on the number 1 and the engine began to die (as suspected it should) retightened and away she went. Next we cracked the #2 line and the only result was free flowing fuel, no change in engine performance. So is the injector bad on #2 or possibly the pump is not working properly or a combination of both?

next step is to replace the injector... any steps we are missing?

also tried tightening the bolts on the plate with the high temp sensor and it slowed the escaping gas but did not stop it or the slow leak of lube oil. Could this be related to the #2 injector not working (loss of compression in the engine ?)

 

[Dennis W.]

Exhaust in Water Jacket Cylinder Not Firing

It has been my experience that if you have exhaust gases coming from a water jacket and no change in performance when a cylinder is deprived of fuel you will find 1) blown head gasket 2) cracked head 3) cracked block. Two and three usually also show water in the oil or oil in the water.

 

[John Nantz]

re injector question

To comment on just the injector issue:

"However, just for fun, we cracked the bolt on the injector line on the number 1 and the engine began to die (as suspected it should) retightened and away she went. Next we cracked the #2 line and the only result was free flowing fuel, no change in engine performance. So is the injector bad on #2 or possibly the pump is not working properly or a combination of both?"

reply: this is not adnormal and I wouldn't suspect a bad injector based on this lack of air in the 2nd injector alone.

It really appears there is still air being sucked into the system somewhere.

Start at the fuel tank connection and work upstream from there checking fittings for tightness and gaskets on the fuel filters. Take a close look at the fuel hoses, especially in the area around the fittings.

Any pressure on the hose at the fitting can cause a pinhole that is almost impossible to see. If you've got the length I'd suggest cutting off, say, an inch of hose at each connection.

With regard to the oil leak, I think someone mentioned about the O-ring valve cover gasket and this is a very likely source.

How old is the engine?

 

[filthy liberal scum]

I am very familar with this engine

It was only manufactured 1978 thru 1980

 

[filthy liberal scum]

that's an indication of air in the system

what's probably happening is its still either pulling air into the sys or it hasn't worked it's way out yet. it will eventually work the air out but it takes a while as only a small portion actually goes into the cylinder the rest is bypassed back to the engine fuel filter.