Engine seems to start but rolls to a stop

[GrowleyMonster]

Originally Posted by JustinT

I've not done a compression check as unsure what I'm doing. A chap locally suggested getting the local garage to do it.

Just a note, this engine, since I have had it, has never been good at cold starts.

A compression check is not particularly complicated. The only real hitch with some engines is finding the correct adapter for your compression gauge. It must fit properly in either glow plug port or injector port.

If you don't have a workshop manual for your engine, get one.
https://www.manualslib.com/products/...0-3965937.html
Having the manual will be a big help in doing stuff like valve adjustment or head removal or replacing rings, stuff like that.

Compression testers are not expensive. Make sure it is rated for diesel engines. Many cheap ones will only work for gas engines because they do not display high enough pressure for a diesel. Most kits should have an adapter that will fit your engine. If not, you will have to get an adapter that will work. These should be common. On some less common engines a used injector must be converted by a machinist into an adapter.

https://www.amazon.com/Paisley-Indus.../dp/B08BZWYHXN

Your engine should have at least 355psi, below which you will not have an easy time starting the engine and you will not have much power if you get it started. 383 - 412 psi is apparently the correct range.

I highly recommend that you use a torque wrench for installing the adapter and then reinstalling the injector. That way everything gets torqued to the factory specs, which you can find online or in the manual for your engine.

Youtube is your friend. A quick search uncovered quite a few videos on your engine, though I was specifically looking for one that shows how to do a compression check on it. My search was not exhaustive and a deeper search will probably find something. Sometimes a video shows stuff better than the manual, but both together is a winning combination.

You can find youtubes showing how to check and compare injector spray patterns, and other troubleshooting and maintenance topics. Watching a vid might give you the confidence to carry on. If you still have not checked injector spray pattern and done a compression check, then obviously you are gonna have to bust some knuckles and turn some wrenches and get a little dirty.

Your engine is relying on you. You are its mommy and daddy and doctor and provider of all good things to it. Don't let it down. Show it that you care, and that it can trust you in all things.

Adjusting decompression levers Bukh DV 2

https://www.youtube.com/watch?v=1_osHWXhV_c

Apparently this is a common issue with these engines, and a very simple one to fix.

Bukh DV20 Injection timing adjustment

https://www.youtube.com/watch?v=QDZfJ-yL5M4

(But don't perform this procedure before injector test, compression test and valve adjustment!)

A couple more to have a look at.

https://www.youtube.com/watch?v=UKMQj1AMk7I

https://www.youtube.com/watch?v=B0diWTupQAE

https://www.youtube.com/watch?v=ANlgDIBQDvM

https://www.youtube.com/shorts/5FRDfEd2OB4
https://fuelflowpro.com/compression-...diesel-engine/

Now, time to gitter done.

[JustinT]

On doing the decompression levers I find a problem:
https://youtube.com/shorts/nPZRVyC0D...pBMWLot-wCTqbr

[Wotname]

Yep, never going to start while that exhaust valve is stuck open!

I suppose you could try freeing it with a tap of the hammer but I think you will end up having to remove the head (at least).

[skipperpete]

See post #4 (deblen), had you followed Len’s advice back in July2023 you’d have been able to fix this. In your video it looks like there’s a lot of sludge and corrosion on the overhead gear, if that’s correct, the same must be true for the bottom end and that doesn’t bode well. At least now we all know why the engine “seems to start but rolls to a stop”.

[JustinT]

Yep. I guess you can lead a horse to water but you can't make a mechanical doofus fix his engine.

[JustinT]

Originally Posted by deblen

You say it "rolls" easily.
Is there a decompressor lever open?
Is there a stuck valve?Remove valve cover & check for valve motion.
Cheers/ Len


https://bukh.dk/upload_dir/docs/FAQ/...%2020%20ME.pdf
https://www.cruisersforum.com/forums...ns-157620.html

Thing's one misses

[JustinT]

Originally Posted by skipperpete

See post #4 (deblen), had you followed Len’s advice back in July2023 you’d have been able to fix this. In your video it looks like there’s a lot of sludge and corrosion on the overhead gear, if that’s correct, the same must be true for the bottom end and that doesn’t bode well. At least now we all know why the engine “seems to start but rolls to a stop”.

Indeed. It actually looks much more messy in the video than in real.
I'm certainly disappointed with myself I didn't follow advice well.

[skipperpete]

Originally Posted by JustinT

Indeed. It actually looks much more messy in the video than in real.
I'm certainly disappointed with myself I didn't follow advice well.

That’s nothing to beat yourself up about ……but the implication now is that first, the valve stuck open THEN got belted back up by the piston so it’s possible that. A. the valve stem is bent B. The valve remains slightly open and C. The pushrod is bent.
The good news is that there’s now a damned good reason why that little engine ALMOST starts, and it can be fixed. Also , you need to find out where and how the water is getting into the crankcase.

[GrowleyMonster]

Originally Posted by JustinT

On doing the decompression levers I find a problem:
https://youtube.com/shorts/nPZRVyC0D...pBMWLot-wCTqbr

Ahhh NOW you are getting your hands dirty! See? That wasn't so bad, and now you have narrowed the problem(s) down a good bit.

Right now, order a couple of head gaskets, because you are fixing to use one, and you will want a spare. Also get a torque wrench if you don't have one. You are gonna have to pull that head. It's not complicated but you do have to torque the head bolts down to the proper torque. But yeah pull the head. Then have a look at that stuck valve. You see that spring underneath the valve end of the rocker? See how it is supposed to pull the valve up tight into its seat when the pushrod and rocker are not pushing it open? How it is supposed to work is there is a camshaft with cams on it that is driven in time with the crankshaft and pistons. The individual cams push up on the pushrods which tips the rocker arm for the valve and opens it even though the spring is trying to keep it closed. As the camshaft turns, it opens an closes each valve at the proper time in the cycle. And so it is stuck. Maybe just a simple stuck and maybe the valve got bent. First, see if it is simply stuck. With a hammer and a piece of wood, try to tap it up into the closed position. If it then moves freely and it appears to be undamaged, you COULD try putting the head back on and reconnecting everything, and going for a start, but honestly once you have pulled the head you may as well pull all the valves and have a GOOD look at the seats and the mating surface of the valves. . I would take the whole darn thing apart, clean it all up good, coat everything with some mystery oil, check the cylinder walls for scoring and look for bits of broken rings, inspect the piston crowns, in fact everything visible with the head off, check it while you got it off. Do not try to reuse the old head gasket. Do not try to improvise one.

I almost forgot. Compare the valve spring with the one for the same valve on the other cylinder. They should be the same height and have approximately the same resistance to compression. If that is not the case, replace it. There is a special tool that makes compressing the spring for valve removal a lot easier. Many parts shops have them and will lend you one.

You could take the entire head to a shop and let them do a complete valve job, polishing and replacing the doodads that need it. Honestly I would be surprised if the valves and seats are all perfectly healthy. I just have a feeling that your engine has seen a lot of neglect and lived a rough life. You can do all that yourself but the temptation is strong to improvise and do stuff with less than shop quality methods and tools. And it will take you some time because you will basically be learning on the job.

What you find when you do the head will tell you what next. Overhaul? Full rebuild? Or just slap it back together and use it till it does a full meltdown on you? If it were my engine I would stick a long shaft outboard on her and take the diesel out of service, and at a minimum, do a full teardown, cleanup, and inspection, then a full rebuild only if indicated. Maybe put the head back on and do that compression test, and if compression is still under about 380, at least replace the rings and try again. If compression is still low, go for rebuild. Make no mistake, your first engine rebuild is a PROJECT with a lot of steps and parts and procedures and checks. Don't be surprised if it takes you a few months as you source stuff and borrow tools and get advice and compare notes. The thing is, if done right, you get, performance wise, basically a brand new engine, one that you literally know inside out.

[JustinT]

Thank you. A lot to chew on there.

[JustinT]

Originally Posted by skipperpete

That’s nothing to beat yourself up about ……but the implication now is that first, the valve stuck open THEN got belted back up by the piston so it’s possible that. A. the valve stem is bent B. The valve remains slightly open and C. The pushrod is bent.
The good news is that there’s now a damned good reason why that little engine ALMOST starts, and it can be fixed. Also , you need to find out where and how the water is getting into the crankcase.

I did remove the pushrod and it is indeed bent.

[JustinT]

Thanks to all the members who have helped me on this thread! I'd have no clue without you all.

[JustinT]

I just went to the boat and the valve is moving freely. Will do more work tomorrow.

[GrowleyMonster]

Originally Posted by JustinT

I did remove the pushrod and it is indeed bent.

Bravo! Just remember nothing happens in a vacuum. SOMETHING caused this to happen, and this happening likely caused something else to happen and so on. Keep investigating.

Also, you can NOT simply drop in a new or salvaged pushrod, close her up, and expect it to run properly. At a bare minimum you will need to adjust your valves. Consult your manual for proper clearance, and pick up a set of feeler gauges. They are cheap.

[JustinT]

Originally Posted by GrowleyMonster

Bravo! Just remember nothing happens in a vacuum. SOMETHING caused this to happen, and this happening likely caused something else to happen and so on. Keep investigating.

Also, you can NOT simply drop in a new or salvaged pushrod, close her up, and expect it to run properly. At a bare minimum you will need to adjust your valves. Consult your manual for proper clearance, and pick up a set of feeler gauges. They are cheap.

Yes, thanks for the note. I have feeler gauges and looking for torque wrenches and gaskets at the moment. Very keen to sort the issue well.