MASE / Yanmar generator problem

[chrisr]

here's one for any serious mechanics out there...

we have a little 5Kva built-in diesel generator. this is a MASE IS 5.0, which has a yanmar L100 AE single cyc diesel engine. mainly runs watermaker but handy for other stuff too

new in 2003 but only 1235hrs

has always run like a swiss watch until recently. fired up after a service and find it won't hold revs under load - apply more than abt 2 amps load and bogs down so badly the output current is useless.

originally thought fuel supply but checked this VERY thoroughly (inc replacing elect fuel pump) and no problems there.

also checked alternator and no problems there either

starting to think the problem is the governor. this is in 2 parts - an external speed control & the internal lever assembly. the external speed control has a couple of springs which we're going to change as soon as we can get them. after that : running out of ideas (short of dismantling the engine and checking the internal lever assembly)

anyone with any relevant experience ? helpful suggestion desperately needed !

cheers,

[Compass790]

My first question would be what was actually done on the service?
Did you do it or a mechanic?
I would suspect fuel as well before governor but you say you've eliminated the fuel possibility.

[Chayal]

Did the problem start after the service, or was the engine giving issues before the service?

If it started after servicing I would recheck what you and or the technician touched.

Assuming it was thoroughly/properly bled after filter change?

[tkeithlu]

I don't qualify as a serious mechanic, but aside from the possibility of a mistake during the service I can't fail to note that you didn't mention checking the injector for a partial blockage or checking the air supply. It's a diesel. If it's got fuel, air, and compression, it should go.

I'll go even farther out on a limb and say that the throttle linkage would be far down the list of my hypotheses of the source of the failure. It's simple, mechanical, and not likely to fail once set correctly. Fuel, air, and compression are at the top of the list.

[Wotname]

You say this generator is built in. Does it still have the original exhaust system or has this been modified to discharge overboard?

If modified, check the complete exhaust remains unrestricted.

Likewise, the fuel tank - has the original tank being replaced with an external supply. I understand you have checked the fuel system 'VERY thoroughly' but ......

In main, I agree with tkeithlu's post above.