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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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  #11  
Old 08-14-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

I am curious as to what you mean by gravity feeding the motor. I do have a spare gas tank but it also has cracks in the line so it won't be the best option.

Do you guys happen to know what ID tubing I will need for the fuel line?
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Old 08-14-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

that means you hold it higher than the fuel inlet on the engine...say hold the bottle fast to the galley sink or companionway above the engine or even in the cockpit and feed the hose to the engine....
but if the motor runs fine using this system then that means you know exactly where your problem is and that is before the engine filter...
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Old 08-15-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

If you go the portable tank route, don't forget that diesels usually have a return fuel line. You need to run that back to the portable tank or you will quickly end up with an empty portable tank and the fuel in the permanent tank.
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Old 08-15-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

Wow I am glad you reminded me of that. I wasn't thinking about that but will be sure to run two lines.
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Old 08-15-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

you know I was going to say that...BUT not all tanks systems and diesels for that matter use return lines...

I do however beleive the 1gm does...

my 2gm had it...

good luck
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Old 08-18-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

Thanks again for all the help. I couldn't have figured this out without you.

The new suction and return lines, gravity fed directly to the motor worked out. However, it was a serious PITA to bleed out all of the air. The gravity aspect allowed me to easily bleed out the air up to the point where you see the red arrow in this picture. I was just loosening the hard flue lines and allowing the siphon action from the fuel tank push the air out. However loosening the hard fuel line directly on top of the red arrow wouldn't happen, UNLESS I loosened the actual part that the red arrow is pointing to. Can someone tell me what that part is, and why it wouldn't allow fuel to gravity flow through it onto the injector?



After I finally figure out that the red arrow part needed to be loosened to allow fuel to pass onto the injector I was completely primed all the way to the injector. I double checked all fittings were tight and tried the motor again and it fired right up.


Now we start a whole new section of engine problems....
During the fuel system work I had been periodically turning over the motor with the engine stop lever pulled up (so motor wouldn't fire) so I could get the fuel pump spinning. As this was happening the engine temp gauge started to go up each time I turned over the motor. There was no fire being created but the temp gauge eventually went all the may to max 120 degrees and stayed there forever. I never once had the high temp alarm sound during the process however.
I am just guessing here but maybe it is a faulty gauge/sender?

Once I got the fuel lines primed and finally started the motor I verified that water was coming out the exhaust as it was running at the dock and it looked great. I ran the motor 10 minutes or so at around 2000 rpms to make sure it was working fine before we started out journey. Water kept coming out the exhaust, motor was warm to the touch but wouldn't burn you unless you left your hand on for a few seconds. We untied the dock lines and started motoring out into the river. The motor was not really struggling but it didn't want to rev up higher than 1800 rpm even if the throttle was pushed all the way forward. I am guessing it was resistance from the prop shaft or something that was overloading the motor. The exhaust was pretty black so I reduced throttle until the revs went down then only gave it enough throttle to get the revs up to 1800 and left it there. The black smoke went away and all was good....For about 60 seconds or so.
Then I noticed white/grey smoke coming from the exhaust and no water was exiting the motor. I quickly made sure my dad didn't close the kingston **** by accident but it was open. I quickly shutdown the motor, ran to the bow and dropped the Danforth S2000 43 lbs anchor (more on this later) and tied off the actor line. The motor was very hot to the touch so I knew something was wrong, but once again I never got a high temp alarm to sound.

When you don't get water flow I immediately think impeller, and luckily the boat had a spare onboard so I go about swapping it out. You can't get to the impeller cover plate unless you remove the lower pulley which was not easy to do without a pulley puller but I got it off. The damn screws were completely stripped out so I had to use vicegrips to remove them. Low and behold the impeller was in great condition, but I ended up swapping it out anyways just because I had the spare. I then started removing hoses and checking to see if they had blockages. All the hoses looked good but the motor inlet water passage had a blockage where the red arrow is.


I used an allen wrench to try and break it up, but I couldn't drag the blockage back to me and it got pushed into the motor. I then removed the thermostat cover and luckily the boat had a spare thermostat as well. However I didn't install it because I didn't want that blockage to get pushed into the new t-stat. I finally got the motor put back together and started it up and we had water coming out the exhaust once again, so I motored up to the anchor line and tried to break it free.

Good God that mother has some holding power. It took multiple attempts motoring from all angles to finally break the anchor from the bottom. Yes I had taken up all of the scope so the anchor line was virtually vertical from the bottom to the boat. I can surely rest easily next time I drop it that i will be safe. I just hope I will be able to break it free

So now we motor back to the dock and tie her off. Seeing as how there is no t-stat the water is not being forced into the motor and just bypassing through the exhaust but I didn't want the impeller just spinning and not flowing water. So here comes the next round of questions...

What would be the best way to force water into the motor and flush out any blockages that are in there? I was thinking about removing the hose marked with the red arrow from the top connection point and installing a plug where you see the blue mark. Then install another hose on the top port (where I just disconnected the first hose) and put a plug in that hose where you see the blue mark.


This should hopefully force all the water into the motor, out through the t-stat housing, and out the exhaust port. I would then redirect the exhaust hose to a bucket to catch the debris so it doesn't cause problems in the exhaust system. UNLESS, you guys tell me that is not needed???

Once the motor has been flushed out for a couple minutes I will reinstall the t-stat and see what happens.

Seeing as how I never got a high temp alarm I need to figure out if something is wrong with the temp sender, so...
Can someone show me where the temp sender would be located and how to diagnose if it is faulty?

If it checks out how do i diagnose the temp gauge to verify it is working properly?

Sorry for the short novel of a post but I have a huge learning curve as this is my first inboard motor, and I have no experience with diesels period.

Thanks again for the help,
Zac
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Old 08-18-2014
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Re: Engine diagnosis Yanmar 7.5 hp...

can you remove the temp sender unit? sometimes they are a pain in the ass...a new one is the real way to see if it good or bad

when you say you turned the engine over thats using the decomp lever right? if not and your compression is good it would be impossible unless of course you had very low compression...

thats a good test btw to find out if you are ok

also you can do a "wet" test with a little oil down the hole...

Im afraid you might of done some damage however with that run

get a thermostat in there asap

there are many diesel owner out there who do the thermostat bypass HOWEVER I forget what it is they do but they weld up a channel or something on the heat exchanger or something

dont quote me on that I just know that if your run thermostat less you have to make sure the water is flowing correctly THROUGH THE ENGINE

a simple way to clean your cooling system is the bucket of vinegar and water solution...

you can use more expensive products but basically fill a bucket with a couple galobs of cheap vinegar...fill rest with water...put intale hose in and run then let SIT. then rinse and do again if you want

it does wonders descaling and decrudding all nooks and crannies.
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Last edited by christian.hess; 08-18-2014 at 12:10 PM.
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Re: Engine diagnosis Yanmar 7.5 hp...

Quote:
Originally Posted by christian.hess View Post
can you remove the temp gauge?

when you say you turned the engine over thats using the decomp lever right? if not and your compression is good it would be impossible unless of course you had very low compression...

thats a good test btw to find out if you are ok

also you can do a "wet" test with a little oil down the hole...

Im afraid you might of done some damage however with that run

get a thermostat in there asap

there are many diesel owner out there who do the thermostat bypass HOWEVER I forget what it is they do but they weld up a channel or something on the heat exchanger or something

dont quote me on that I just know that if your run thermostat less you have to make sure the water is flowing correctly THROUGH THE ENGINE

a simple way to clean your cooling system is the bucket of vinegar and water solution...

you can use more expensive products but basically fill a bucket with a couple galobs of cheap vinegar...fill rest with water...put intale hose in and run then let SIT. then rinse and do again if you want

it does wonders descaling and decrudding all nooks and crannies.

When I was bleeding the air in the fuel system I was using electric starter to turn the motor so the decompression handle was closed. I did not try to spin the motor manually with the decompression valve closed but I am pretty sure I have good compression. I will report back later today to verify.

I will try the vinegar and water trick to get some of that crap out of the engine. How long should the mixture soak inside the motor before I flush it out?
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Re: Engine diagnosis Yanmar 7.5 hp...

overnight works...
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Re: Engine diagnosis Yanmar 7.5 hp...

Oh yeah I forgot to mention...Where is the temp sender unit? I have no idea where it is, but I will remove it if I can find it.
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