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Discussion Starter #1 (Edited)
Hi there, pleased to make your acquaintance. I found this site because I'm looking for some help with this Deutz I've got here.

I just started working at a place that has a 4 cyl deutz running a generator. I've been monitoring the fuel usage and I am noticing an increase in consumption. The only thing I can think of is maybe a clogged air filter but since it has an oil bath filter, that doesn't seem too likely.

Any ideas? Consumption has gone from .6ish gal/hr to .9ish gal/hr week over week (the last two weeks).

Thanks,

Edit: The load remains constant. The only variable is the length of time running per day.
 

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Winterized fuel can cause a slight increase in fuel consumption.
 

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Welcome to 4btswaps......You did not mention if you have a water cooled, oil cooled or an air cooled Deutz diesel engine. You also did not mention if it is turbocharged. I assume it is a naturally aspirated air cooled diesel engine, and if that is the case, the fan could be worn, or the fan clutch could be bad. If the fan were running all of the time at full capacity that would suck down a lot of power and thus increase fuel consumption. Another possibility is that the cylinder fins and oil cooler fins are dirty. Like any other air cooled engine, they run very hot. Blow out the squirly oil cooler line and cylinder fins with compressed air. Because this is a generator engine, I would expect it to have a high temperature sensor on the cylinder heads. How old is the oil in the engine? Perhaps it has broken down and needs to be changed. If the engine is turbocharged, the wastegate could be malfunctioning, or the turbocharger is just internally worn. Lots of possibilities. What is the model of the engine you have?

Chris
 

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Discussion Starter #5
Hi K-Tron, Thanks for the comeback. Ya sorry, it is an air-cooled, naturally aspirated, 4 cyl, diesel. Don't know the model # but I bet you nailed it with the oil cooler lines and fins. I have cleaned them once but not for a bit now. I've just changed the oil about 125 hrs ago. I'll clean the fins again and see if that helps.

Thanks, I'll post back and letcha know :idea:
 

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Discussion Starter #6
Well I'm back. Things I know as fact now are 1) The cleaning of the fins didn't make a difference (they weren't really clogged or dirty). 2) The fan clutch is not working but I don't know if it ever was working (at least not since I've been here. 3) Oil consumption has most definitely increased. It was averaging 1 litre per 120 hrs until last week when, after changing the oil, it increased to 2 litres in only 65 hrs of runtime. We are using Lucas oil stabilizer. Blow-by has definitely increased as well.
What I don't know for a fact is if fuel consumption really did go up or not. Now that I think about it, there is a possibility, that there could be a dent in the bottom of the tank that is not visible. Since I'm calculating fuel level by dipping the tank, and the tank is a horizontal cylinder, it would appear to be consuming more fuel when the tank is in the bottom 3rd of the tank than when it was in the top 3rd of the tank. I have refilled the tank now and am monitoring fuel consumption to compare it to what the consumption was from the top portion of tank before.
I'll know by the end of the week is fuel consumption has actually increased or not but in the meantime, is there anything you can think of now that might cause an increase both fuel and oil consumption?
 

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Discussion Starter #7
Okay so, after 73 hours of runtime from a full tank (66"), we're down to 59" and the result is a consumption rate of .88 GPH. That compares with 71 hours of runtime from a full tank (66") to 60.25" for a result of .68 GPH in September.

So a roughly 30% increase in fuel consumption coupled with an increase in blow-by and oil consumption.

Any ideas?

Thanks,

Ron
 

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Hi Ron,
I have been giving your scenario a good bit of thought. I think your oil consumption and additional fuel consumption is due to a lack of a substantial load on the generator. While looking at my F4L912 brochure I see that it is a 3.7 liter engine producing 45 horsepower at 1800rpm. With a stated 0.370lb/hp hour maximum fuel consumption that is 16.65lbs of fuel per hour, or a maximum of 2.34 gallons per hour of fuel used. When you reverse your calculations using the numbers you provided, at 0.68 gph the engine is only pulling a 13 horsepower load, and at 0.88gph the engine is only pulling a 17 horsepower load. An engine of that size is likely coupled to a 25-30KW generator. I believe your generator has been run too long without enough of a load on it to keep cylinder temperatures hot enough to burn all of the fuel provided. (Research wet-stacking) Chances are the cylinders are now glazed over and the compression is suffering, and the rings are having a hard time sealing up. Does your generator have a built in auxiliary electric heater for load testing? Perhaps you should run the generator at full load for a couple of hours to help the rings re-seat and restore compression. If that does not fix your oil consumption problem, you might have to hone the cylinders and re-ring the engine. Out of curiosity, how many hours are on this generator, and what oil are you running in the engine? You should be running a good quality 15W40 CF-4 oil in it. Your oil changes should be every 250 hours on a genset.

The 912/913/914 series Deutz Diesel engines are relatively simple. Short of an external oil leak (leaking oil cooler, loose or cracked pushrod covers, loose oil filter, oil pan leak, oil line to fan, crank seals), the only places that oil could be disappearing from would be through worn valve guides or worn piston rings. Since there is an increase in blowby I would say the rings are on their way out (Again research wet-stacking). The 911/912/913/914 engines do not have wrist pin seals, so no possibility of leaking wrist pin seals. Is the engine smoking all of the time? If the cylinder walls are glazed over, or the engine has bad rings it will smoke all of the time. If the engine has bad valve guides, run the engine at speed to get the heads/valves and guides hot, then let it idle. If it smokes noticeably more on deceleration the valve guides are worn.

Deutz used several different fans on their engines, some were direct driven and ran all of the time, others had a fan which was controlled by engine oil pressure, others had a fan which was controlled by exhaust manifold temperature. The last is the most complex, there is a thermostat on the bottom of the exhaust manifold which determines how much oil pressure can pass through the pilot valve to the fan. It is a relatively complex temperature switch and can be calibrated. If the fan is not coming on, the temperature switch can be bypassed so that the fan runs 100% of the time. There is a bit to it, I can send you a Deutz service manual if you need. You should be able to tell when it is running. It will make a good bit of fan noise and you will feel a jet of hot air blowing off of the cylinders. If it werent getting enough cooling air it would lock up on you in short order. All of the air cooled Deutz diesel engines have a fan belt sensor which shuts the engine off if the fan belt fails.

Try topping off the oil and running the generator under full load for a couple of hours. I would bet that the oil consumption will drop off. Fuel consumption might increase due to the test, but should stabilize again once the rings have re-seated. Should that be, it would be a good idea to load test the generator more often to keep it from wet-stacking again and again.

Chris
 
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Discussion Starter #9
Hi Chris, thank-you very much for the time and thought you've put into this. A service manual would certainly be a good thing to have. I was unable to find a model # for the engine though. We are using 15W40 with Lucas stabilizer and they have told me to change oil/filter every 500 hours. There is no hour meter on the unit so I have been logging the hours manually for my own purposes but have no idea how many hours are on the engine in total.
Even after 500 hours of runtime, the oil is very clean and still a little hard to see on the dipstick, which seems to me to contradict the idea of burning too much fuel.
I think you are right about it being lightly loaded though. After initial start up of the engine, when I turn the power switch on, there is barely an audible difference in engine load. It is a 35Kw genset and I don't know if there is an auxilliary heater for load testing. Yes the engine smokes all of the time but in the beginning (I arrived here Sept 1) any blow-by was unnoticeable, if there was any. Lots of blue smoke out the exhaust pipe though. The blow-by is easily noticeable because the engine is indoors.

Thanks again,

Ron
 

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Discussion Starter #10 (Edited)
Aha! Found the plate, it is a F4L912.

Not that it matters to your assessment above, which I think you're right about, but in the process of going through your calculations, I realized that 1) you are probably using US gallons and 2) I am not actually burning diesel fuel. I am burning aviation fuel (roughly 1/2 pound lighter than diesel) and calculating Imperial gallons.

So the mathematical result may differ but probably not enough to make a difference. I am going to pull the rear panel off the generator to look for a way to increase the load. No auxiliary load to be found.

Thanks
 

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Im not sure you will be able to find an additional onboard resistor bank if it does not clearly have one. The onboard resistor bank is basically a giant coiled ni-chrome wire which is essentially a large electrical short that heats up and glows. They were common on a lot of the older Detroit Diesel Delco generators I am more familiar with. You can simply add a few electric heaters to help load up your generator. There should be a voltage and ammeter on your genset so you can measure what percentage you are loading the generator. If not, you can figure out how much to load the generator based on the Hz output. If it drops below much below 60Hz you have reached the nameplate capacity of the generator. I just sent you a private message. If you email me, I can send you some Deutz 912 series manuals and literature

Chris
 
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