Fuel injection pump problems - Yanmar 3GM30 1987

[eublem]

Hello,
I have a Yanmar 3GM30 1987 diesel engine in my sailboat. The engine starts easily but runs with a too high RPM (and it wont stop without restricting fuel or air). The previous owner is certain it's something wrong with the fuel injection pump.

Does this sound plausible to you? and why/- not? 


// Halvard

[zaphod]

Do you mean the engine over revs a lot or a little? If you start a diesel engine and it accelerates to high rpm without increasing throttle position it is what is referred to as a "runaway". It can be caused by engine oil leaking into the cylinders and combusting like fuel. It can also happen if someone accidentally puts gasoline in the diesel tank.

If it just over-revs a little bit it could be a simple matter of adjusting the governor.

You should definitely have a diesel mechanic check it out.

[eublem]

Thanks for your feedback! It was very educational for me (several aha-moments).

I spoke more with the previous owner. He believe the engine is getting too much diesel. He opened up one diesel injection pump valve (?)  and changed the o-ring, copper plate and the spring. He believe the one valve/mechanism(?) isn't adjusted correctly, and fueling the engine with too much diesel.

I am not entirely sure what valve he is talking about, but I assumed it was the piston valve...

[sitara]

Get a diesel mechanic to look at the engine. The Yanmar engines are well built and very reliable and can perform well for a long time if looked after well. How many hours on the engine? And please let us know the outcomes.

[zaphod]

May 24, 2019 21:50:54 GMT eublem said:

Thanks for your feedback! It was very educational for me (several aha-moments).

I spoke more with the previous owner. He believe the engine is getting too much diesel. He opened up one diesel injection pump valve (?)  and changed the o-ring, copper plate and the spring. He believe the one valve/mechanism(?) isn't adjusted correctly, and fueling the engine with too much diesel.

I am not entirely sure what valve he is talking about, but I assumed it was the piston valve...

I suspect the previous owner doesn't know what he is doing. If he has been opening up the injector pump and tinkering with it you should definitely have a mechanic look at it. Injector pumps need to be set up and calibrated properly. The last time I had an injector pump overhaul the tech calibrated the pump and injectors, and bench tested it for a full 24hrs on a machine in his shop.

You still havent told us what exactly you mean by too fast. Is it just idling at an unusually high rpm, or is it revving up a lot? What rpms are you seeing?

[partman]

I am very satisfied with my Yanmar engine. Be sure to show it to a mechanic and do regular maintenance. It will be a long use.