3GM30 gurus please (yes, fuel related)

[sonAdmiralson]

Im having trouble w an 850 hr 3GM30F. Wont start. Ive had the injectors tested, all the lines cleaned and primed. My question is this: if/when these primary pumps go, do they go all at once or just peter out. Could it need shimming @800 hrs? The last time we tried it, it "pipped" from the one rich injector, stuttered, but never caught. When I went to check the lift pump, the feedline was dry. However I was with a certified Yanmar mech anic, and he did bleed the lines at the injectors. (Only the feed lines however). The lift pump cked ok. In the service manual it says you bleed the return lines First.

[a64pilot]

It should not need shimming and unlikely the HP pump is bad.
I’d start by ensuring that the fuel shut off mechanism is fully open, then proceed to ensure that there is no possible fuel clog in the supply system.
Just as a swag it sounds a lot like a clogged supply dip tube to me.

[sonAdmiralson]

In the log it shows the raycor separator had clogged once, with "additives". How to judge that ? I could pull fuel with a little mouth suction to help prime it.

[RaymondR]

800 hours is not long enough to wear out anything on a Yanmar.

Bad fuel, clogged or crimped fuel line, clogged filters or air leak into the fuel system between the lift pump and the fuel tank.

[maine50]

Might want to try fuel from a 5 gal jug straight to engine bypassing fuel tank, fuel lines, fuel filters etc, This will tell you where the problem area is.

[roverhi]

The return lines go to a ‘T’ fitting and back to the tank on mine. No need to bleed that I can see. If you’ve got compression and the air intake isn’t blocked engine should run if it’s getting fuel. Any chance it could be the shut off mechanism?? The shaft on mine froze in the open position. Gentle tapping with a hammer, penetrating oil and rotating shaft finally loosened it up.

[bobnlesley]

Originally Posted by roverhi

The return lines go to a ‘T’ fitting and back to the tank on mine. No need to bleed that I can see...

Agreed, we became experts at bleeding ours a few months back.

Worth a check is to take off the Yanmar pre-crimped fuel lines (one to lift pump and short one from there to secondary filter) and give the banjoend fittings a really good tug & twist; ours appeared good, but after weeks of searching we eventually realised that they moved slightly and depending on their precise position they leaked either a lot, a little, or no air whatsoever. Carefully cut off the crimps and fit new flexible hoses clamped to the end fittings with jubilee-clips.