803 Bogs Down and dies at 85% Load

Anyone have any ideas as to what would cause a newly rebuilt motor to start to bog down after about 15 minutes at 100% load? Is this something that is motor related or gen related? IIRC from the info I got, the motor runs fine without a load so it seems to me to be a gen problem. So assuming that, what part of the gen would cause the motor to bog down after 15 min? Possibly the VR?

Opinions please. I do not have the genny in hand so I am limited as to what I can do, say, or info I can provide.

It's possible that the overload relay is reading the output current wrong, or the load indicator is off. I'd try running the genset at 80% on the panel indicator and see if it starts to show the same symptom. And verify that it's indicating properly with a clamp-on meter on the output terminals to load.

If both are reading properly, then it's possibly fuel supply issue. It's possible that the filters/lines are clogged and it's not getting enough fuel at the 100% load to keep up with the load.

Also Check air filter, you may remove this long enough to check this if you are running in a clean area without dust or anything else that could be sucked in. I normally run a fresh rebuild up to 75% for the first hour before running 100%, but that's just me.

What constitutes "newly rebuilt" to you?
Has this set ever run right?
Have you ever seen it "bog down"?
What constitutes, "bog down"? Engine speed slows? Gen set rejects load? Overload function kicks in?
How long has the set been sitting before someone started to fool with it?
How much load are you putting on it?
Who "rebuilt it"?
Has someone been "repairing" it besides the engine?

We need background before we can troubleshoot. Otherwise it's just shooting in the dark.

I would NEVER run a "newly rebuilt" engine at 100% load to start with.

csheath said:

I would NEVER run a "newly rebuilt" engine at 100% load to start with.

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If you were using a load bank, how high would you go? Do you recommend X hours to then test to 100%?

I am not a generator specialist but from a mechanic point of view I probably would run at 50 percent for 10 hours or so then maybe 75 for another 10.

That said, it's probably covered in one of the manuals.

That is not nearly enough information to take more than a guess. You need to see it run and hopefully shoot some video. Check all the fluids. Check the air filter. What do you see/hear/smell when it bogs down. Does it slowly bog or does it go down fast.

Is this a unit you are trying to help someone with or looking to purchase?

Yeah not enough meat to go with these potatoes unfortunately. All new injectors? Completely clean fuel system? Air filter? Easy enough to pull the air filter to see if its crushing after extended runs. Let us help you, by helping us .

I would bet your running low on the fuel supplied to the injectors. Are the fuel filters new? Does the pump put out the pressure and gpm the manual states?

Also check to make sure you didn't put 40 weight oil in a new rebuild with less than 100 hours. Also break in a generator like you would a fine automobile. Did you flush the fuel tank first and change the fuel filters??

Does it bog down where it shuts off? Does it sound like its shutting off?
Could be the fuel pump is failing and can't keep up with the needed flow. Since the motor is demanding more fuel as your load increases, means the fuel pump will pump faster and run hotter.

Well, an update on this. I picked up the genset couple of weeks ago and have been looking at potential issues. To answer a previous question, newly rebuilt as in Dec 17 and only 8 hours on the motor.
It was taking up to 90 sec for the genset to turn off so I knew that I would have to fix the issue. Turns out the lever, fuel, stop/run has three holes in it. The lever from the selonoid fuel is supposed to be bolted to the middle hole. Mine is bolted to the lower hole so the fuel was never fully in the stop position.

Now, I am wondering if this is the reason the genset bogs down after 15 min at 85% load. I'm not fully into this but as it is part of the governing system I think this may connected. Does this stop/run switch stop the fuel flow (does not appear to) or stop the injector pumps?

Also, I have a leaking gear cover oil seal and when running, there is oil coming from the #3 and #4 injector pumps at the shims. Going to replace the gear cover seal but not sure what to do about the injector pumps.....

Glad I checked fluids as there was a one quart overfill in the genset.

Also needed to add half gallon of water/antifreeze.

In Figure 6 of the 24P Fuel Selonoid it shows the link bolted to the top hole.

In Figure 9 of the 24P (Govenor) it shows the link bolted to the middle hole.

Mine is bolted to the bottom hole.......which is right?

If you go to the TM forum, there should also be in addition to the TM's, a procedure for properly adjusting the linkage. Most linkage problem are a result of someone fooling around with the linkage, and not reading the book/information.

USAMilRet said:

In Figure 6 of the 24P Fuel Selonoid it shows the link bolted to the top hole.

In Figure 9 of the 24P (Govenor) it shows the link bolted to the middle hole.

Mine is bolted to the bottom hole.......which is right?

Click to expand...

There are 2 holes at the top of the lever on the motor, it should be connected to the bottom hole at the top.

The stop/run switch makes the injector pumps cut off the flow of fuel.

For the oil leak at the fuel pumps, try tightening the nut on the hold downs to see if that helps.

I still say its a fuel delivery problem, i.e. fuel pump or something in the tank that is floating around blocking the pickup tube.

jamawieb said:

There are 2 holes at the top of the lever on the motor, it should be connected to the bottom hole at the top.

The stop/run switch makes the injector pumps cut off the flow of fuel.

For the oil leak at the fuel pumps, try tightening the nut on the hold downs to see if that helps.

I still say its a fuel delivery problem, i.e. fuel pump or something in the tank that is floating around blocking the pickup tube.

Click to expand...

I agree. if it runs fine on 100 percent for fifteen minutes then bogs tells me it is just running low on fuel pressure. i would put an inline gauge in the primary fuel line so i could monitor the primary fuel pressure as it fails. i would bet you have a bad electric fuel pump that fades as it gets hot. also don't forget the fuel return system. if it has a restriction and slowly builds to much pressure it will also restrict the delivery. make sure the vent in the tank is working

Hopefully I will be able to hook it up to my 12500 watt variable home made load bank (hope to finish it today) so that I can put a heavy load on it.

This generator was running fine prior to the rebuild. It is a 2009 model which had 218 hours on it before the rebuild. Onlyy after the rebuild did this issue arise. I am not saying that any of the suggestions of things to do won't get done.

I am trying to get an understanding of how the lever, fuel, stop/run interacts with the fuel injector pump rack and how moving this lever which moves the rack either allows fuel to be pumped by the injector pumps or not. What is the interface between the rack and injector pumps and how does moving the rack disengaged the pumps.

I have the documents downloaded but as indicated, none on the three figures shows the same thing. One figure shows the linkage bolted to the lower hole and the other two images show alignment to the center (lower of the two top holes) hole but NOWHERE that I can find specifies exactly which hole the linkage is bolted to. The TM shows the adjustement procedures but again, does not specify in writing which hole to use.

I just took a look at my 803A and the as installed condition of my fuel solenoid agrees with "FIGURE 6. Fuel Solenoid Installation" in ARMY TM 9-2815-253-24P and jamawieb's post #16. You have found an error in the TM's "FIGURE 9. Governor System" with regard to the Fuel Solenoid linkage connection.

Basically, there are levers on the injector pumps that fit into the fuel rail. The levers move left to right, when they are all the way to the left (towards the radiator) the injector pumps are off (no fuel), then when the rail moves the levers all the way to the right, fuel is fully open.