Engine Compression

[papatractor]

I have assembled my freshly rebuilt 2305 Yanmar engine. I have rebuilt a few gas engines, but this is my first diesel. Before I put on the valve cover, I rotated the crank with a socket wrench to verify oil was reaching the valve train. I could not feel a compression stroke in the motor. With a gas motor, you can feel the compression stroke resistance when you rotate it with a socket wrench.

The engine is assembled except for valve cover, injector tubes that connect to injectors and fuel pump, exhaust manifold.

Should I feel the resistance when I rotate the motor.

All thoughts are appreciated!

 

[Bladehauler]

yes , diesel should have 375 -500 lbs of compression . you dont have the valves set to tight do you ? I'm assuming the glowplugs are installed in the head as well as the injectors ?

 

[papatractor]

The valves are going up and down as I rotate the engine. Glow plugs and injectors are installed. Did not install the tube that connects injectors to the pump, but there is not any noticeable pressure coming through the top of the injectors. I can feel some compression, when I turn it, but not much.

I am thinking the #1 piston was not at TDC of it's compression stroke when I installed the timing gears. Anyway to check that without taking timing cover off and watching line up marks with the intake and exhaust valve?

 

[papatractor]

I was able to verify that the timing between the cam and crank are good. The flywheel has each TDC piston marked on it. Verified it is on TDC during compression stroke. I am going to put it together and crank it up. One thing that I am afraid I screwed up is the injection pump timing. Live and learn...we will see if it fires up. I am gaining an understanding of the differences between gas and diesel engines...the hard way.

 

[RickB]

I was able to verify that the timing between the cam and crank are good. The flywheel has each TDC piston marked on it. Verified it is on TDC during compression stroke. I am going to put it together and crank it up. One thing that I am afraid I screwed up is the injection pump timing. Live and learn...we will see if it fires up. I am gaining an understanding of the differences between gas and diesel engines...the hard way.

If you can't feel the compression of a diesel as you roll it over, you have more than the pump timing screwed up. Might as welll start backtracking now rather than put more together, then take it ALL apart.

 

[papatractor]

I was able to figure it out. Little embarrassing, but hopefully this will save some time for the next guy. The head was machined and I simply bolted on the valve train thinking it would be close enough. Planned to adjust the valves as a tuning step. Fact is, the mill was enough to keep all the valves open...thus could not feel compression. Quick little adjustment, slapped the rest of the parts on and turned it over. It started!!! I just got lucky with the Fuel Pump timing. Ran great during the initial start-up and had no leaks. The saga could be over!