803 Bogs Down and dies at 85% Load

[justacitizen]

after all of this guessing and chasing it would probably benefit you to run a compression check on all cylinders. then you will know for sure and can cross that off of your list before advancing on into the fuel system. confirm compression and air then fuel. i assume that while you had the front cover off you checked the cam timing???

 

[USAMilRet]

Got it running. Ran at various loads for various times. Could not get my load bank to put more than 60%, or it kills the genset.

I have 4 x 10 ohm in parallel with 2 x 5 ohm parallel. If I drop the 5 ohm, I'm down to 60%.

Video of today's run posting shortly.

 

[USAMilRet]

after all of this guessing and chasing it would probably benefit you to run a compression check on all cylinders. then you will know for sure and can cross that off of your list before advancing on into the fuel system. confirm compression and air then fuel. i assume that while you had the front cover off you checked the cam timing???

Don't think this is necessary at this time.

 

[98G]

Ohm?

Amps, or am I missing something?

 

[USAMilRet]

Ohms. My load bank is based on furnace elec elements. Each element of the primary 4 are 5000 watt "resisters" with the other two elements a 4800 watt element cut in two for 2 x 2400 watt elements or 2 x 5 ohms of resistanc.

So to get to 60% load, I hook up the 4 5000 watt (4 x 10 ohm) in parallel. You would think that this is 20000 watts but it is not. I am interested in the resistance in a parallel circuit of 4 x 10 ohm in parallel is 2.5 ohms of resistance. Less resistance more current flow..

If V=I^2 R then 240VAC/2.5 ohms = 96 Amps ^2 or 9.798A per resistor X 4 resistors is 39.2Amps.

The 39.2Amps is 75% of 52Amps so math says the % load as shown on the meter must be calculated differently. Knowing me, probably math is wrong.

 

[USAMilRet]

Video of today's workings.......

https://youtu.be/iYa5ghlHAUU

 

[98G]

Ohms. My load bank is based on furnace elec elements. Each element of the primary 4 are 5000 watt "resisters" with the other two elements a 4800 watt element cut in two for 2 x 2400 watt elements or 2 x 5 ohms of resistanc.

So to get to 60% load, I hook up the 4 5000 watt (4 x 10 ohm) in parallel. You would think that this is 20000 watts but it is not. I am interested in the resistance in a parallel circuit of 4 x 10 ohm in parallel is 2.5 ohms of resistance. Less resistance more current flow..

If V=I^2 R then 240VAC/2.5 ohms = 96 Amps ^2 or 9.798A per resistor X 4 resistors is 39.2Amps.

The 39.2Amps is 75% of 52Amps so math says the % load as shown on the meter must be calculated differently. Knowing me, probably math is wrong.

Interesting. I've never calculated it that way. (Obviously I was "missing something")

I'm coming at the generator stuff from a different perspective. I learned electricity as an offshoot of welding. I've only used Ohms for calculating the current carrying capacity of cables.

For a field expedient load bank I use a plasma cutter and adjust the output. I calculate based on amperage... example - a 50 amp plasma cutter turned halfway up will run on a MEP802, but turn it up any further and the 802 cuts out. An 802 is rated for 26amps, so this makes sense...

 

[98G]

I've been thinking....


Let's change units of measure for a moment.

We have a MEP803, nominally a 10kW generator.

The military underrates them. Typically they'll happily make 120%...

You have 20,000 watts (labeled) of load. The generator is pushed right at the 60% mark. Without fiddling with ohms to amps to kW conversion, that would seem to be 12kW of load, on a 10kW genset. Which is right where I'd expect it to be....

I readily concede I may be missing something. You're telling me that your 20kW labeled load isn't really 20kW. I suspect that your calculations drop the line losses and tell us what the 'load bank' is putting out and not what it's taking in from the genset.

I await input from those more knowledgeable than myself and hope to learn...

 

[justacitizen]

i could be wrong but 6psi primary fuel pressure seems low. i don't know what the spec is for sure but experience tells me it should be more like 15 psi. this would definitely cause similar symptoms. maybe someone who knows the part number and mfg of the fuel pump can google and find out.

 

[csheath]

i could be wrong but 6psi primary fuel pressure seems low. i don't know what the spec is for sure but experience tells me it should be more like 15 psi. this would definitely cause similar symptoms. maybe someone who knows the part number and mfg of the fuel pump can google and find out.

6 psi is within specs. My 803 runs fine under full load at 6 psi fuel pressure.

 

[Zed254]

I'm having a difficult time finding specs on the specified Airtex E1074 Main Fuel Pump. I can find plenty of data on the Aux Fuel Pump.....from the Ops Manual -
Auxiliary Fuel Pump:
Voltage Rating 24 VDC
Delivery Pressure 5.0-6.5 psi (34.5-65.5 kPa) range

My notes say for Primary: Facet 40193 main fuel pump: 30psi max, 10 gallon/hour – Facet is a PoS.....Airtex E8131 provides 35 gallon/hour at 10 – 14psi (substitute for OEM). (1 Inventory).

The Airtex E8131 specs out at Rockauto as: https://www.rockauto.com/en/moreinfo.php?pk=293415&jsn=3

Several members pointed to a suspect fuel pump early in this thread - #10, #12, #17.

The Tier II document - TB 11-6115-741-24 - describes some additional fittings needed for Primary Fuel Pump change out Airtex to Purolator. Note the Airtex E8131 is not a direct drop in for the E1074 - you will need some fittings.

See post #31 for details on installation of Airtex E8131. The inline fuel filter is the Airtex G-17.

 

[csheath]

I ran a pressure and volume test on my Airtex E1074 just out of curiosity. The dead head pressure was 6 PSI and volume was ¼ gal in 60 seconds = 32 ounces per min = 15 GPH. I have loaded my unit to 50 amps with no problem and run it for two hours at 40 amps every month in addition to 50+ hours of outages on my all electric house with a well and 3.5 ton AC. Nary a hiccup!

 

[USAMilRet]

I've been thinking....


Let's change units of measure for a moment.

We have a MEP803, nominally a 10kW generator.

The military underrates them. Typically they'll happily make 120%...

You have 20,000 watts (labeled) of load. The generator is pushed right at the 60% mark. Without fiddling with ohms to amps to kW conversion, that would seem to be 12kW of load, on a 10kW genset. Which is right where I'd expect it to be....

I readily concede I may be missing something. You're telling me that your 20kW labeled load isn't really 20kW. I suspect that your calculations drop the line losses and tell us what the 'load bank' is putting out and not what it's taking in from the genset.

I await input from those more knowledgeable than myself and hope to learn...

I have to rethink my calculations. Getting senile in my old age. V=IR

 

[justacitizen]

ok if the fuel delivery is in spec the next thing would be to check and see if the governor is opening the rack enough at high demand. i suspect it is because of the black smoke during high loads. so lets assume the governor is working as it should then the next would be air volume. can you check the air inlet system for restrictions? i know of at least one time a fuel pump was reworked and finally a tractor was sold because of issues and the new owner found a rag in the intake manifold when he was taking the head off for rebuild. took out the rag and all was fine. sometimes people will stuff a rag into the intake and forget to take it out before the crank the engine. next i would adjust the valves.

 

[USAMilRet]

Other stuff I have been doing as well...

The IP67 Connector to the generator had to be offset by about 1 inch due to the hinge bracket at the top not letting it seat fully into the recess. It fits nice except you could not open the cover far enough to plug in the cable. So I got a HD 4X4X2 plastic box and cut holes in the cover and the bottom and attached the IP67 and Generator together. The ring for the cable protection at the generator was a tough deal to get aligned properly to get the 3.5 inch nut because the box had been sealed at that time. This was the only way to get it installed properly using nuts and bolts for the connector to box interface.




My simple ground solution for the genset case. Yes it is still bonded at this time.





My free steel drums courtesy of my neighbor. These are two of the four I am to get. Three will be for diesel fuel management/storage and the fourth for used oil and other like materials. I don't even have to paint them but they are sand colored not the camo that my genset is painted. For the fuel experts, should I even bother trying to clean the interiors once fully drained? Seems to me that this would be just enough lubricant to add to the diesel fuel with no issues.






Now for the meat of it. Here is todays video of the genset running at 77$ to 80% about 39 amps per leg. When I try to up to above 80%, bogs down, gauges fluctuate all over the place mostly down though, and oil pressure drops causing an oil low pressure fault and shutdown.

 

[USAMilRet]

https://www.youtube.com/watch?v=OsiQ-q9v4_g

 

[USAMilRet]

https://www.youtube.com/watch?v=wIMkec_oTz8

 

[USAMilRet]

https://www.youtube.com/watch?v=bLrlE7ZNuPw

 

[USAMilRet]

https://www.youtube.com/watch?v=-WamvT8wl5Q

 

[justacitizen]

low oil pressure shutdown? could the L.O.P shutdown switch be bad? might try single weight oil 30w or 40w and see if the engine will run long enough to get the rated load up to 100%. things are improving though. does this engine have an engine oil cooler???