fuel injection problem Yanmar 2QM15

[Bryanaw40]

After leaving the gas dock after letting the engine idle slowly (while waiting for a pump out) for about 1/2 hour, the engine seemed to stall (just as I was traversing the main fairway with traffic coming from both direction!). I shifted to neutral and lowered the throttle and it recovered. I put it in gear and applied power and it seemed to stall again. I slowed the engine and shifted to neutral again and it stalled. I restarted the engine, shifted to forward and applied power and it took off. I motored into a small bay outside the marina and ran it up to full speed and it seemed to run fine. I ran it for another 1/2 hour just to make sure it was running OK and returned to the dock without incident.

The next day, I thought it prudent to change the primary and secondary fuel filters and look for water, etc. Filters looked fine but I changed them anyway. I put the system back together and bled the system as described in the Yanmar Service Manual. I have done this 3 times in the three years I have had the boat because I change the filters every year and have always been successful with this operation. However, this time, I could not get the first cylinder (closest cylinder to the pump) high pressure fuel line to bleed any fuel. The second or aft most cylinder line bled fine.

Got any ideas? If it is a defective fuel injection pump, can a new pump can be installed or "dropped in" without adjustment or special tools? I keep my boat in Sarnia Ontario and all I have not heard any successful diesel engine repair stories and am reluctant to turn my engine over to one of the locals for this reason.

I realize it is difficult to troubleshoot an injection problem with the information I have provided but hope someone has had similar experience and can relate the steps needed to repair the problem.

bryan

[Alan Wheeler]

Don't think about a new pump. The price will make you go all weak at the knees and you may have to sit down for a while
BUT, you can remove your pump and send it away to be tested and repaired. BUT, the timing IS MOST IMPORTANT, So before you take the pump off, mark the shaft coupling(should be a coupling, but yell if it's not) on both sides, so as you can fit it back together again, with the identical alignment. It should be as simple as that. If your engine has clocked up a few hours, then send the injectors with it and have both overhauled. The injectors don't cost too much to do.

[BC Mike]

Try the Yanmar help line. I believe the pump rarely causes problems. Mine still works fine since 1979. Have the injectors serviced. Other than that I think you are being to nice to your engine. They can get a bit low on compression after many years, but this will show up with hard to start problems especially when cold. A couple of drops of oil on the pistons will help with starting. Good luck.
Michael

[Bryanaw40]

Thanks Mike and Alan for the reply and for the advice. My injector pump is driven by a cam shaft with two cams, one for each high pressure injector pipe/injector. Thanks for the tip on alignment. I will certainly study the service manual if I pull the pump to send away. I am leaning toward sending it someplace unless I am able to get #1 to bleed. I am going to try once more. If I can't get it working, I plan to send it to Torrenens on the west side of the state (Michigan).

As suggested, I will send the injectors as well.

As far as compression, I have not had it tested but I think it is solid. The engine starts quickly, even when the temp drops into the 40's. No smoke, black, white or otherwise. Old boat but the previous and only owner rarely left the dock and seemed to really take care of things. He use the boat as a yacht club cottage.

Bryan

[Alan Wheeler]

I am not familiar with the pump, but lets go back a step. For air to be in the system, air has to get there. So you need to look for something wrong. Check all crox nuts on all the metal pipe work to and from injectors. Check for cracks in joints. When the engine is working, you may notice a slight weep around a possible problem area. If it is in the main No.1 injector line, then when the engine is stopped, it may bleed air back in. However, in saying that, I don't think this is your problem. To go from running to sudden stop, it has to be a major amount of air entering the pump. Most likely it is even before the pump itself.

[Bryanaw40]

Alan,

I think the air got in when I was changing the filters (primary and secondary) when looking for the root cause of my stalling episode after leaving the pump-out dock.

I talked over the phone with a mechanic on the west side of Michigan at Torrensen's Marina and he suggested I loosen a fitting on the pump that appears to be the nipple for the #1 cylinder HP pipe. The nipple happens to have a spring, o-ring and something called a delivery valve nested inside. If air is into the pump, it sometimes get stuck at this particular valve. The air lock is broke by loosening this fitting/assembly and bleeding. the service manual does not mention this possible bleed point.

I bled this fitting followed by bleeding the HP pipe at the injector. tightened things up and started the engine. It fired immediately and ran great! I did some dock trials (engaging the transmission and applying power while tied to the dock) after warming up the engine...not even one miss-fire or anything that duplicated the problem I had at the pump-out dock.

I think I also might have found the root cause of the stalling problem when leaving the pump-out dock. The primary filters I have been using (2 left by the previous owner and 1 I bought based on these part numbers) does not fit the primary filter holder. They are approx. 3/8" short!! This short length causes the filter to slip off the suction pipe leading to the injector pipe, causing ALL fuel to bypass the filter element. Too bad it took me 3 filter changes to figure out that it falls in the first hour or two of operation! Ugh! I have a secondary filter/water separator but believe the filtration is a bit more course. Can't be sure the bypassed primary filter was the root cause but two step filtration is the standard on diesels for a reason.

Thanks again for the feedback.
bryan