no compression

[MicHughV]

As a follow up, I had a similar instance once, where the machine shop, had honed the valve seats some, and after re-installing everything, the valves would not seal properly, and I had to adjust all the valve clearances.
There should be a mark on the flywheel, or pullet denoting TDC, but I find watching the valve position on each cylinder to be easier, especially so, with the cam cover off.

[Cheechako]

Yeah, identify if the valves are closing fully. When they appear closed you should be able to rock the rocker arm and notice it has a gap. Did the shop also surface the head flat?
On each cylinder you can observe the intake valve open, then shut. Before the exhaust valve opens you should have a loose rocker.

[MicHughV]

From the sounds of it.....it appears that the head work done might be the culprit here, but a simple valve clearance check and re-set ought to solve the issue.
Always difficult to solve these problems from a few printed words without having the engine in front of you.
Re-surfacing the head and valve seats invariably lead to valve seating issues...which in turn lead to zero compression.
Not sure where the cam chain/belt is on this engine, but also worth a look for correct tension, positioning, etc.

[Wotname]

^^ Camshaft is direct gear driven on the Yanmar xGMxx series.

[skipperpete]

Ok, here’s a few suggestions about why your engine won’t start and no offense is intended if I include mention of things you’ve done that might be totally wrong or inept, these are all things I’ve actually encountered.
1. The head gasket is upside down
2. The head bolt tensions were wrong and it’s blown the gasket
3. You left something on the block deck that stopped the head from sitting flat and sealing properly. (Old gasket adhesion)?
4. You used the old head gasket.
5. You dropped crap into the pushrod gallery and compromised the cam follower sockets….. I’ll get back to this later!
6. You lost all the valve stem caps and now the cam timing is off
7. The rocker shaft is installed incorrectly.
8. The valve grind went badly and now the stem heights are too high so the clearances don’t exist at all
9. The precom chambers are incorrectly installed.
10. The injectors are leaking compression.
There’s more, but that’s enough for starters. You had a running engine that smoked a bit at startup and now after trying to fix that, you have a non running engine with what you think is low or zero compression and IF that’s the case, it’s likely because…..and I mean this in the nicest possible way…. You or the shop got something very wrong. There’s still a vague possibility that the exhaust is seriously plugged or there’s a shop cloth in the intake manifold.
Getting back to #5, if anything gets into the cam follower sockets, the pushrod height is effectively increased and if you’re one of those guys that refits a head without backing off the tappet adjusters you might bend a pushrod, worst case scenario is you spin it over and bend a valve stem AND a pushrod. Good luck with getting it running, I’m looking forward to hearing your next update and hopefully the cause of the no start. Oh, #11 was going to be crossed injector pipes, hard to do on a 3GM but way easy on other diesels.

[MicHughV]

We should start the CF diesel repair shop here...

[ncbrew]

Originally Posted by MicHughV

We should start the CF diesel repair shop here...

I got the engine running. It has a sometimes hard knock and at times runs rough. It seems to run OK at 2000 RPM.
I am going to reset the valves tomorrow. Today is Sunday.
I am not sure how to start adjusting the valves. When both valves on number 1 cylinder per are closed is that where I start?
Thanks again
NCbrew

[Cheechako]

Originally Posted by ncbrew

I got the engine running. It has a sometimes hard knock and at times runs rough. It seems to run OK at 2000 RPM.
I am going to reset the valves tomorrow. Today is Sunday.
I am not sure how to start adjusting the valves. When both valves on number 1 cylinder per are closed is that where I start?
Thanks again
NCbrew

Rotate the flywheel, on each cylinder you can observe the intake valve open, then shut. Before the exhaust valve opens you should have a loose rocker if the valves are closing fully and the flywheel is at TDC. Top Dead Center. When they appear closed you should be able to rock the rocker arm and notice it has a gap. Adjust the valve clearance. Now move on to the next cylinder starting with the intake valve open/closed again.

[David Mathis]

Check the valve settings and timing. If the valves are too tight and not seating, it won;t be possible to build compression as the air will flow past the unseated valve. If the timing is incorrect, the valves could be open during the compression stroke then close during the intake phase.

[Shaneesprit]

I once rebuilt an engine, not the same model and with a bad hangover and had no compression, those inlet and exhaust valves were always tricky, on the model - any way managed to put the Inlet and Exhaust valves in the wrong holes 😂.

[GrowleyMonster]

I would bet a dollar to a donut that it is not one, but all of your exhaust valves failing to close all the way. There are other things it could be but that is the prime suspect and it is easy to check them and adjust if necessary. A relapped head or block, new head gasket, etc, can put you off by as much as 10 thousandths easily. OTOH if they are WAY WAY WAY off, there is likely some issue with the reassembly and you need a mechanic to check it out, IMHO.

Youtube is your friend. Usually. Adjust your BS filters and watch more than one video. Adjusting valves is not super mysterious and every diesel owner should know how to do this, certainly before ever pulling his first head. Amazing how valve clearance being right on the money helps an engine with a couple thousand hours on it run like new. If you get a pro to do it, WATCH HIM and get him to explain as he works. Being a mechanic makes some guys grouchy by nature so try not to ruffle feathers but make sure he understands that you want to have a good understanding of how to do it yourself by the time he presents you with the bill.

[GrowleyMonster]

Originally Posted by skipperpete

Ok, here’s a few suggestions about why your engine won’t start and no offense is intended if I include mention of things you’ve done that might be totally wrong or inept, these are all things I’ve actually encountered.
1. The head gasket is upside down
2. The head bolt tensions were wrong and it’s blown the gasket
3. You left something on the block deck that stopped the head from sitting flat and sealing properly. (Old gasket adhesion)?
4. You used the old head gasket.
5. You dropped crap into the pushrod gallery and compromised the cam follower sockets….. I’ll get back to this later!
6. You lost all the valve stem caps and now the cam timing is off
7. The rocker shaft is installed incorrectly.
8. The valve grind went badly and now the stem heights are too high so the clearances don’t exist at all
9. The precom chambers are incorrectly installed.
10. The injectors are leaking compression.
There’s more, but that’s enough for starters. You had a running engine that smoked a bit at startup and now after trying to fix that, you have a non running engine with what you think is low or zero compression and IF that’s the case, it’s likely because…..and I mean this in the nicest possible way…. You or the shop got something very wrong. There’s still a vague possibility that the exhaust is seriously plugged or there’s a shop cloth in the intake manifold.
Getting back to #5, if anything gets into the cam follower sockets, the pushrod height is effectively increased and if you’re one of those guys that refits a head without backing off the tappet adjusters you might bend a pushrod, worst case scenario is you spin it over and bend a valve stem AND a pushrod. Good luck with getting it running, I’m looking forward to hearing your next update and hopefully the cause of the no start. Oh, #11 was going to be crossed injector pipes, hard to do on a 3GM but way easy on other diesels.

Wow, very comprehensive and well thought list there, Pete. Saving that.

[Carl-T705]

It's a little late but, Do you have an engine service manual?? Engines that do not have the fuel system primed , as in running out of fuel or being assembled and not priming the fuel system will spin over easily because there is nothing more than air being compressed. You may not have had any issue other that no fuel .

[ncbrew]

Originally Posted by MicHughV

Well, simple enuff....if you can rotate the engine, just watch the valves, with the cover off....when the inlet valve is all the way down on a particular cylinder, that means the exhaust valve is likely to be fully closed, easy to see by watching the cam lobe on the camshaft controlling those valves. Check the gap of the closed valve and adjust to recommended clearance. Repeat for the exhaust valve and move to the next cylinder.
rinse and repeat.
After installing new head gaskets, etc, these gaps are likely to be off.

SO I removed the starter Motor and there are marks there showing when pistons 1, 2, and 3 are at TDC. I set the mark to piston #1 and adjusted the #1 valves. I then rotated the engine and did the same for cylinders 2 and 3. The valves are correct but it would still not fire. My assistant noted some black blow-by in 2 of the injectors. He asked me did I torqued the nuts holding down the injectors. I told him I did not and he tighten them more and it started. It still smokes but I guess I can live with that. At least it is running and I can now go sailing.

Thanks to all that gave me advice.

As in the song..."Thats what friends are for"

[skipperpete]

Originally Posted by ncbrew

I got the engine running. It has a sometimes hard knock and at times runs rough. It seems to run OK at 2000 RPM.
I am going to reset the valves tomorrow. Today is Sunday.
I am not sure how to start adjusting the valves. When both valves on number 1 cylinder per are closed is that where I start?
Thanks again
NCbrew

Well done, thanks for the update. You must have had some compression if she fired up. This probably doesn’t concern what you’re doing with a valve adjustment but Yanmar numbers the GM cylinders from the flywheel, this is only relevant if you’re doing the injection timing. The rough running might be due to air in the fuel system, that makes the engine clatter a bit more than usual but there’s also the possibility that the precom lower chamber is mis aligned. This can only happen if the little dowel pin is missing but it’s worth a mention since the precombustion chambers were out at some point.