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Discussion Starter #1
Having previous gas engine experience, I've been asked to look at a M18 diesel on a sailboat. The engine supposedly ran prior to the new owner but it hasn't run since. I admit I'm a newbie with diesels but a lot of the components are similar. After initial inspection, I was able to turn the engine through 2 cylinder cycles with the crank pulley by hand. The glow plugs and the injectors are in and tight and the compression relief lever is not engaged. I removed the valve cover and observed the valves operating properly. My concern is I may have major issues (head/rings/...) because the engine could be turned by hand with occasional resistance. I'm familiar with gas engines using initial compression relief on pull start engines. So my questions are: should I be able to turn over the engine through all cycles by hand? Is there an initial compression relief (other than the spring loaded one on the back of the valve cover)?

A couple of side questions: Is this a 2 cycle or 4 cycle engine? Do the injectors fire during intake stroke or after compression is achieved?

B
 

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All small marine diesels including the Universals are 4 stroke. The injection is near TDC, similar to when the spark plug fires in a gasoline engine. With the compression release flipped, you should be able to easily rotate the engine by hand. With the release off, it will take a wrench on the crank or something similar to turn it over. Sounds like you have the compression release activated.
 

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Discussion Starter #4
Thanks for the info. It's as I suspected. With the valve cover off the compression release level is off and you can turn the engine threw all 8 cycles. I'm suspecting head gasket or something common to both cylinders because both compression strokes don't produce significant resistance.
 

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On a diesel number 1 problem is air in the fuel and engine is not getting fuel at the injector. most missed diagnosed problem is low compression if the fuel pump has any air in the system the timed injection pump will not pump fuel to the injectors. if the engine has compression with the compression release closed it should start if it has fuel. remove the injectors and turn it over to see if it is getting fuel. and you have look very closely because on that size engine it will not be very much fuel. you can also just remove the fuel line at the injector to check for fuel but you will not see the fuel spray pattern that way.
 

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Discussion Starter #6
Overboard- good point. So knowing the high pressure injector lines are removed, should there still be compression when you turn the engine over?
 

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Overboard- good point. So knowing the high pressure injector lines are removed, should there still be compression when you turn the engine over?
Yes, removing the fuel lines should not affect compression.
 

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You should be able to turn the engine over with the hand crank. Otherwise why would there be one? But it should not be easy to do so. There should be considerable resistance as each cylinder comes up to compression. If it turns over more or less "easily" that indicates a problem such as head gasket, cracked head, etc. Least expensive would be valve adjustment too tight and not allowing valves to close completely. Just like the compression release being engaged. This often shows up as a loud top end knock when the engine is hot, long before it fails to run.
 

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The engine supposedly ran prior to the new owner but it hasn't run since.
Can you expand on this? Did the current owner ever see the engine running, or was it just a rumor? If so, what’s happened to it since? Did it sit, was any maintenance performed?
 

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Discussion Starter #10
The boat was a bank reposition. My friend has had it for 5-6 years and has been fixing it up. Nothing was done to the engine to this point other than purchasing a new starter, alternator, impeller, and glow plugs. He asked me to come and help him get the engine running since the rest of the boat looks great!. Going in blind, he said that the engine turns, without the starter, by hand. He did say that it was hard at first but loosened up over time. When I went there, the engine does indeed turn over by hand using the 4-5" crank pulley with some periodic resistance but not alot. I pulled the valve cover and the valves cycle properly and all end up with clearance throughout the cycles, so no broken valve stems! I seriously doubt that the engine was ever winterized but I can see coolant through the water pump opening. I was reluctant to pull the head without checking in this forum about the compression. At this point, I believe the head to be the main issue and the next step.
 

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Stuck rings?? Solvent soak, wait, Turn by hand with decompress engaged to prevent hydrolock. Try it now. Good compression on a hand crank is pretty noticeable.
 

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Is it getting fuel, while cranking the starter? Have you changed the fuel filters and bled the injector lines? Always start with fuel on a diesel. Blown head gaskets or cracks often don’t prevent them from running, they leak and run badly.

Bank repos take a long time. I’m guessing it hasn’t run or been maintained in years. Assume engine oil has been replaced too, although, would not impact starting.
 

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Discussion Starter #13
At this point, there are no fuel lines connected or starter. Just trying to figure out how deep I have to go into the engine. I'll start with the head an work from there. I bet the valves aren't seating properly.
 

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Are you going to do a compression test, before digging into the valves or head?
 

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Discussion Starter #15
Don't plan too since I shouldn't be able to turn the crank pully by hand. Clearly I need some more resistance during the compression strokes.
 

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I would do a compressor test first. this is a small 2 cylinder engine and with a dry cylinder walls it will turn over easier by hand then it would if you get it spinning with a starter. sometimes when they sit for a while they do not develop much compression when turing slow. WD 40 in the cylinder and then check compression. I have seen many a old diesel that has sat for a long time fire right up with a good fuel supply.
 

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Up to you, but beware of surgery before the diagnosis. Just tearing down old diesels can introduce issues. If you're planning to overhaul one way or the other, it makes sense. Once you pull that head, you’ll need to have it ground to put it back.
 

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Could just be the rings are frozen from sitting dry so long. I would be tempted first to pull the injectors so you could squirt some penetrating oil in the cylinders.
 

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If you get a low compression reading, put a little oil in the cylinders and take another reading.
The added oil wont help bad valves/seats
First goal is to get it started
 

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I don't think my last comment posted. I have the same engine. Before you tear into the heads. Does the fuel pump run when you turn the key to the on position? Is the fuel shutoff between the tank and the engine on? Have you used all the bleeder valves to get the air out of the lines? These motors are super resilient but they hate air in the lines. Also glow plug for at least 30 seconds.

I've attached the owners manual which should be helpful. Page 29 has the bleed procedure. View attachment 136942
 
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