yanmar diesel engine

[Doug Christensen]

we have a 3 cyl yanmar Model #3TNA72 UJ. The engine will not start. The motor had been rebuilt before we bought it.
we checked the timing, compresion (455,455,475) glow plugs. Rebuilt the injector pump and had the injectors checked, replaced the primary fuel pump and fuel lines. We have tried to bleed the system numerous times but we can not get the air out of the injector lines. It seems as though we have them bled (we get no air bubbles) but when we turn it over to try to start it, it gets air in the system again. we have tried this numerous times and are not getting anywhere. Even if you let it sit overnight there will be air bubbles in the system. we can not find any leaks in the injector lines

 

[Tx Jim]

Maybe you have a crack in the supply line from tank to the filter? I've seen them let air in them but not leak fuel out. I would try pull starting it if it has a manual trans.

 

[RodinNS]

You could try rigging up something to induce a bit of air pressure on the fuel tank to help with bleeding. By a bit... I mean 1-3 psi. Just enough to help fuel flow. Keep in mind that the tank will NOT be a pressure vessle and it will not take much more than that to make it swell. That may also help you find any leaks...
Another possibility... I've seen the fuel manifold of the pump develop a crack... this happened once on a Ford I looked at with a Kiki unit pump situated in the engine... There the leak was not easily detectable.

Rod

 

[Dave in Tx]

Does the engine have a mechanical fuel pump or an electric?? I"m asking about the charge pump for the injector pump. Has to have charge pressure. The mechanical pumps can sometimes put air in the system. Change to automotive electrical pump and bleed til you have no air. Also check that the solenoid is turning the pump on.

 

[Nofbdybs]

Here is the procedure for bleeding a Yanmar diesel.


I have bled mine a few times, and it starts the first time, everytime after this process.

http://www.hoyetractor.com/bleed.htm