30kw Katolight Generator (JD 4024TF) is surging without load on cold start

[greenmojo]

Hello all you fellow rural and JD geniuses!

I have an interesting problem, but I do not know where to start exactly. This just started happening yesterday - We have a Katolight generator that surges terribly on a cold-start, for up to a good minute or so until it warms up or load is applied. It is a JD 4024TF.

Last night, I could hear the surging / struggling idle - so I ran out to find it bouncing surging quite badly about once every 1.5 seconds, and emitting quite a bit of black smoke out of the exhaust during this surging.

1) I shut it down, changed the fuel filter, but this didn't resolve the problem.

2) It is a generator, so I immediately thought it could the AVR (automatic voltage regulator) - so I lowered the stability setting to the lowest (most stable), and turned down the underfrequency adjustment - no real difference.

3) What I did notice, as it warmed a bit, it began to settle and no longer bounce/surge - also, when I apply any load from 1kw to 10kw, it instantly levels out and sounds perfect.

With the black smoke, and it surging, to me it sounds like a fuel issue, but I wasn't sure where to check - the fuel filter is new, I don't see any loose connections and it doesn't appear to be losing prime after sitting.

Could this be an issue with the fuel rail or a governor spring (is this even a thing?)?

Any insight would be so helpful. I've included a YouTube video, the engine wasn't cold - it was warmed up and running stable about an hour or more earlier, so the bouncing isn't quite as pronounced, but you can see what I am talking about. In the video, the surging goes stable when the load of about 1000 watts is applied.

 

[ponytug]

I don't know your particular engine, but on any diesel I would have similar thoughts:
Bad fuel (water), air leaking into the fuel line (e.g. cracked hose, loose connection, including a fuel filter leaking air), something sticky in the governor linkage come to mind. I would focus on the connections and hoses as those are likely to arise on storage.
How is the exhaust temperature? (higher than normal temperatures are suggestive of excess fuel, which is suggestive of an air leak)

All the best,

Peter

 

[greenmojo]

I don't know your particular engine, but on any diesel I would have similar thoughts:
Bad fuel (water), air leaking into the fuel line (e.g. cracked hose, loose connection, including a fuel filter leaking air), something sticky in the governor linkage come to mind. I would focus on the connections and hoses as those are likely to arise on storage.
How is the exhaust temperature? (higher than normal temperatures are suggestive of excess fuel, which is suggestive of an air leak)

All the best,

Peter

Thank you Peter! I went over the fuel lines pretty quickly, but I will take a closer look in the next few minutes - I didn't even think to look at exhaust temperature and that makes complete sense, I will measure those.

I opened up the governor housing and watched the governor bouncing (over reacting) - but it smooths out the moment it warms up or has load on it. Then I have to let it cool down for an hour or so to get it to lope again.

This is over my head, but as I learn more, I can catch a breath every now and then.

 

[Jchonline]

I have always heard diesel generators do better under a decent load (40% or higher) but not sure why. Anyone have insight?

 

[LittleBill21]

I have always heard diesel generators do better under a decent load (40% or higher) but not sure why. Anyone have insight?

that is only to deal with wet stacking, which takes a pretty decent long time to occur. like hundreds to thousands of hours. This was common the MEP military generators