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Help adjusting droop on John Deere 4045

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Bergz22

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One of the boats have a 4045 John Deere with a Stanadyne DB4 pump. Someone has messed with the droop screw on it. I read the service manual, but it’s still not clear to me.
I need to have it set at 1800 rpm loaded. I’m confused on if I adjust the throttle to 1800 loaded, then adjust droop at no load?
 
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Bergz22

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Bergz22

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thepumpguysc said:
Yes run it at full load, 1800
Then adj the droop in/clockwise to raise the hertz/60 or out to lower.
Click to expand...

The screw was turned all the way out. Without knowing that I adjusted the throttle arm to raise the rpm back up to 1800.

Is there a way to start over with the pump on the engine?
 
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thepumpguysc

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U have to remove the top cover..
Screw the droop screw to get 7-12 coils on the screw.. then screw the movable internal screw until it just touches the spring..
THAT will get u started..
 
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Bergz22

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thepumpguysc said:
U have to remove the top cover..
Screw the droop screw to get 7-12 coils on the screw.. then screw the movable internal screw until it just touches the spring..
THAT will get u started..
Click to expand...

Oh boy. Ok. The reason that it was messed with is the generator was set at 1830-1835 no load. It would vary between 1750-1800 depending on load.

After I do what you told me, If I understand this right, I should adjust the throttle arm to get 1800 rpm full load. And then at no load adjust the droop screw for 3-5%?
 
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thepumpguysc

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1800 is FULL LOAD rpm..
So it will be 1800 @ 60hz..
U may fine tune the throttle AND the droop screw to achieve that..
BUT.. u have to have a starting point.. see adjustment in previous
post..
 
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Bergz22

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thepumpguysc said:
1800 is FULL LOAD rpm..
So it will be 1800 @ 60hz..
U may fine tune the throttle AND the droop screw to achieve that..
BUT.. u have to have a starting point.. see adjustment in previous
post..
Click to expand...

I understand that. I’m trying to ask what droop is and what it does so I can understand.
 
John C.

John C.

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On the big gensets I worked on in the navy, the droop was how far the engine would slow down when a load was applied. The units I worked on had hydraulic governors and a dial right on the front that was used to adjust it when we did things like install new injectors. Since we support nuke plants the engine was only allowed to drop a few rpm anytime a load as applied or removed except if the reactor fill was initiated. I've seen it on smaller gensets but would think that the absolute horsepower of the engine was be a limiting factor. Some of the generator guys here can explain it a lot better I'm sure.
 
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MarshallPowerGen

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Droop is usually used for paralleling IIRC, all you should need to do is set it to maintain HZ from no-load to full load.

I was going to type a whole thing about counting turns from fully out to fully in and starting back at the halfway point, but thepumpguysc gave you the best info on how to start. After that you should be able to set HZ at no load and then adjust under load to maintain. If not using a load bank and using the boat as a load, I'd say disconnect any sensitive electronics to play it safe, and then be able to use the breaker to test between unloaded and loaded.
 
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Birken Vogt

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Here is how I would do it. Set the droop screw wherever you suspect is right. Load the set to 100% of its normal load. Carefully adjust the throttle to 60.0 Hz. Then remove load. If it stays below 63 Hz and does not hunt then you are as close as you are going to get with a mechanical governor.
 
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Bergz22

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MarshallPowerGen said:
Droop is usually used for paralleling IIRC, all you should need to do is set it to maintain HZ from no-load to full load.

I was going to type a whole thing about counting turns from fully out to fully in and starting back at the halfway point, but thepumpguysc gave you the best info on how to start. After that you should be able to set HZ at no load and then adjust under load to maintain. If not using a load bank and using the boat as a load, I'd say disconnect any sensitive electronics to play it safe, and then be able to use the breaker to test between unloaded and loaded.
Click to expand...

I originally had the engine set at 1850 no load. It would vary between 1800 and 1760 depending on load. I personally think the generator is too small for the boat. (45 kw).

Does the droop setting have anything to do with the rpm dropping when loaded?

From every thing I’ve read. I adjust the engine throttle to run 1800 rpm full load. Then when I remove load this is where the droop setting comes into play.
 
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Birken Vogt

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If it is a mechanical governor, then it is always going to lose some RPM as load comes on.

Droop is how much RPM is lost from no-load to full-load.

It is a matter of setting the adjustments to do what you want.

You would like the RPM drop to be as little as possible so it is running close to 60 Hz under all conditions.

But if there is too little droop, then the engine might become unstable and hunt.

So you set it up to be as sensitive as it can without hunting. Set the throttle lever on the side to 1800 at full load and then remove all load and be sure the RPM does not rise too much. Up to 63 Hz is usually fine for no load. 1890 RPM.
 
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Bergz22

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Birken Vogt said:
If it is a mechanical governor, then it is always going to lose some RPM as load comes on.

Droop is how much RPM is lost from no-load to full-load.

It is a matter of setting the adjustments to do what you want.

You would like the RPM drop to be as little as possible so it is running close to 60 Hz under all conditions.

But if there is too little droop, then the engine might become unstable and hunt.

So you set it up to be as sensitive as it can without hunting. Set the throttle lever on the side to 1800 at full load and then remove all load and be sure the RPM does not rise too much. Up to 63 Hz is usually fine for no load. 1890 RPM.
Click to expand...

Thank you for the answer. Yes it is mechanical. I wish we had electronic engines here. I think I understand. Droop controls how sensitive the governor is to load changes. If I make it too sensitive it will hunt, the rpm will fluctuate to much between 25, 50, 75, 100% and zero load.
 
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Bergz22

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I could easily swap out the pump and send it to a pump shop to get fixed. I’m trying to learn as much as I can.

I’m the only mechanic here, and for the industry I’m in I’m young. All of the older guys have retired. There’s really no one left here knows about this, plus I work on 330, 311, 3304, 353, 3-71, 6-71, 6v-53, 12v-71, kta-19, 4405. Some of the information is hard to find on some of these.
 
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Birken Vogt

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Electronic governors are not necessarily electronic engines either. On a Stanadyne pump like that they just replace the top cover with one that contains a governor actuator, which is just a device that manipulates the shutdown linkage directly. Then you set the mechanical governor higher, up and out of the way so to speak, and the electronic governor pulls it back down to 1800 on the button. Electronic is nice but mechanical is nice in its own way.
 
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