Starting to get scared about this engine..

[roy]

A little update on my adventures with my MD6A that has not been preforming properly..brbr

Yesterday (Saturday), I installed the rebuilt fuel injectors and took the boat out for a test drive. While the boat does preform better, it still seems there is something wrong.brbr

I can go about 2 times faster (my knott meter is not functioning) with the new injectors, but several of the symptoms have not changed.brbr

1. At about 1/2 throttle and above, I get the black exhaust smoke and no increase in RPMs or boat speed.brbr

2. The sound of the engine has not changed much that I can tell. I was told by a diesel mechanic that the engine didn't sound right and that I was only running on one cylinder. I was expecting to hear twice as many popping sounds per second if the second cylinder was firing.brbr

When the injectors were out, I did crank the flywheel and did see fuel squirt sequentially out of the fuel pump. Also, the fuel filters were either changed or cleaned and the electric fuel pump was changed out.

thanks,
groundhogbrbr_______________________________________________
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[stevebirch2002]

Have you checked that teh prop is adjusted at teh correct place for
neutral. May be an idea to have seperate control for revs and for prop
pitch. Just na idea

Steve



Steve Birch (Technical)

 

[shanachie70]

Hi Groundhog,
If your have the combi gear, I would guess that the fuel linkage to the combi is not synchronized with the pitch. This would cause an over load due to too much pitch for the amount of fuel advanced by the linkage to the injection pump.

To test for a dead injector ( any diesel ) slack the fuel pipe nut at the injector. You will hear a change in engine sound, and in the case of a twin cylinder such as the MD6A, if one cylinder is dead, slacking the gland nut on the live cylinder will cause the engine to die for lack of fuel.

Rule of thumb for diesels smoking; grey, or greyish white smoke indicates a lube oil problem, i.e bad rings or leaky valve guides. Black smoke is caused from overload, or from bad timing. In the case of the MD6A this can be cause be a faulty adjustment on the fuel linkage as mentioned earlier, or more unlikely the fuel injection pump has been moved on it's mounting bolts advancing the fine timing, thus causing the engine to emit black smoke. Bad injectors will also cause blak smoke, but you've had yours rebuilt so you can rule this out.

I would suggest that you check the fine timing on your injection pump as outlined in the MD6A shop manual. You will need a smallish mirror and a flashlight, plus a flat blade screwdriver. Make sure that the mark is aligned with the pointer. This is a very critical adjustment.

If you find that the mark and pointer don't coincide, slack the mounting nuts for the fuel injection pump, also the fuel nuts at the filter and the return line on top of the pump, so there is no binding. The injector lines must be disconnected from the pump. Turn the pump body 'til the pointer splits the mark, as shown in the manual. Tighten the mounting nuts and re-check the alignment of mark and pointer.

The fuel linkage to the combi control can be adjusted with the boat under way. Bring the engine up to where it begins to smoke. Slack the stop nuts on the linkage rod.backing the nuts off a considerable bit, adjust the rod until smoking stops. Advance control until smoking occurs again and readjust. In lieu of that, go with a two lever control system, leaving the combi lever to control the pitch and a second lever to control the fuel injection pump.

Regards,

Don

 

[moondance5003]

Have you made sure your air flow is good? Clean filters and plenty
of air. This will increase black smoke at higher throttle because of
incomplete burn. If good, then check compression.

 

[groundhogyh]

On the MD6A, I think there is not too much to the air filter.
I had it off and cleaned it with carburator cleaner spray. It is just like a metal horn type thing about 6 inches long and a metal screen at the end.

Thanks for the idea though.
groundhog