Onan DJE compression testing

Now that, hopefully, my project with restoring this generator is
moving farther along, I want to do something to ascertain its
condition and assess its remaining life.
I can test the following:
1. Check compression. I know that I need to remove injection nozzles
for that. The manual does not say what thread is there. Can I use a
"regular" compression tester or do I need a special adaptor.
I do not presently own any tester, but could buy one, I am sure I
would find uses for one anyway. Also, how difficult/dangerous is it
to attempt to remove injection nozzles, just how much can Imess up.
2. Check cylinder condition, the "ridge" at the top, carbon deposits.
Can I somehow check the crankshaft/pushrod "play" on the cheap without
disassembling the engine?
3. Check its function at the rated load of 6 kw. To that end, I bought
a $8.00 220V 4.5 Kw heater element, and will additionally plug in a
room heater that is 1.5KW. It should handle the load with no loss of
voltage or rpm, right?
Any other ideas? What else can I inspect to estimate its condition?
thanks
i
Reply to
Ignoramus21494
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I've heard that messing with diesel injectors in any way (unless they have failed) is a really bad idea. Apparently just disconnecting the lines and reconnecting them can change things enough to mess up the timing and seals would need replacement if the injectors were removed.
I don't think you need to go to anywhere near the level of inspection you mention to get a good idea of the condition. I'd suggest the following as a good check:
1. Replace the oil filters and open the old ones to inspect for metal particles, etc. A small amount should be normal, but anything significant or large would be a problem.
2. Drain (and refill) the oil and inspect the old oil's condition and any sludge that comes out.
3. If possible shine a light in the drain hole and try to see how clean what you can see looks.
4. Look in the exhaust ports if possible to get an idea of the level of carbon buildup.
5. Test under load, 6 kw for "full load" with a logging DMM to find the high and low frequency and voltage recorded with large load changes. Anything within +/- 2 Hz and +/- 10 Vac for a 6kw load pickup / drop I would consider quite good. Note that the voltage and frequency should return to normal within a second or so. If the voltage or frequency droops under load then the governor or regulator need attention.
6. Test short duration overload, try about 8 kw for a couple minutes and see if the engine has any difficulty. That amount of overload should be well within the units short duration capabilities. The data plate on the generator head should list the continuous and peak ratings.
7. An extended run under full rated load (6 kw), for at least 1 hour will tell a lot. If you have an infrared temperature probe take readings on the generator head and various engine points noting the rise from the starting point. See if the generator head temp rise is within what is listed on it's data plate.
8. Listen for anything that doesn't sound right like bearing noise. Use a mechanics stethoscope to try to isolate anything odd.
In my experience most anything diesel tends to be rather ruggedly built and will generally outlast you if it gets some basic care. Just be sure to either use something like Diesel Stabil in your standby fuel supply or use your house heating oil (diesel) supply (if you have one) as your fuel source since it will see reasonable turnover. The only significant difference between #2 diesel fuel and #2 heating oil is the transportation fuel taxes on the "diesel". The #2 heating oil is also sold as "off road diesel" for non taxable use.
Those are my suggestions based on my limited experience with diesel generators (I have a 25kw ex mil set). I'm sure other folks here will have good suggestions as well.
Pete C.
Ignoramus21494 wrote:
Reply to
Pete C.
Now you are starting to scare me.
Repeat after me: "Do no harm". Concentrate on making the thing run nicely and do the job that you want done. Keep it simple and if it ain't broke, there is nothing to be gained by fixing it.
Vaughn
Reply to
Vaughn
YES!!! Vaughn is right unless there is a need to diagnose a problem forget compression tests. Special tools cost bucks low end diesel psi is about 425. If you want to get a good idea on condition call a generator shop and ask what they will charge you for a load bank test. And while you are there you can pick the tech's brain! Dave
Reply to
Dave Morrison
I agree with you and others who said the same thing, and will abandon this idea.
makes sense. Do I need to drain oil to replace a filter?
I did that recently and it was black, but homogenous.
Very little carbon buildup. Again, I could try to make pictures.
Will do, sand the "logging" DMM.
Makes sense. It will be convenient to try 7.5 KW.
I can easily do that indeed.
Yes, thanks.
Which one is that, MEP-005A?
i
Reply to
Ignoramus21494
I already have my poor man's load bank: a universal 4500W heating element, a 1500W room heater, and 1500W electric kettle.
i
Reply to
Ignoramus21494
Inducing dirt into the fuel system is a common problem when you remove the injector lines or pump. once you get some crap in the lines or pump intake you will have continious problems. Dont try to fix whats not broke.
Black smoke is an indication of a bad injector with improper spray pattern... white smoke is caused by poor compression. These are only general rules.
John
Reply to
john
Far more interesting, the set I have is 25kw 230v 3ph 1,200rpm with an International UD9 engine. It has diesel injectors *and* a carb and spark plugs. It's vintage 1944, the engine has no glow plugs and is designed to start in any weather.
There are three valves per cylinder, one of them opens to a "starting chamber" with a spark plug. When this valve is open the compression ratio is lowered and the carb is enabled so you can run on gas. Once it's warmed up you flip a switch to turn on the diesel supply to the injectors and flip a lever that closes the starting valves and disables the carb.
This was also the first diesel engine I ever worked on and was very educational. It purrs like Godzilla. It's also very stable and has a flywheel that has to weigh a couple hundred pounds.
A few other interesting feature due to it being designed for very extended operation. The coolant system is non pressurized so you can check and top it off with the generator running. Oil is the same with an extended fill port and a dipstick that is marked "this side engine stop" and "this side engine running"
All in all it's a very cool unit that I got as the high bidder for $100.00
Pete C.
Ignoramus21494 wrote:
Reply to
Pete C.
I am very impressed. Sounds like a very fun machine, I wonder why they do not make them like that any more. Did you have to do a lot of repairs to it?
i
Reply to
Ignoramus21494
Virtually no repairs. The thing is rather bulletproof especially running at 1,200 rpm. It also has a port on the front for crank start in case the batteries are dead.
Pete C.
Ignoramus21494 wrote:
Reply to
Pete C.
Diesel Injectors are NOT Rocket Science, but you do need very specific tools to work on them. These tools are expensive, and not commonly available on the consumer level. Taking injectors out and reinstalling them is no big deal, as long as you use reasonable mechanical care. When installing injectors in most diesel engines, one MUST replace the Copper Washer that seals the injector tip into the head. This is a soft copper washer that is compressed, and conforms to the injector/head interface, and is a REPLACEMENT ITEM, whenever the injector is installed. They cost just a few pennies, but you MUST replace them whenever the injector is removed/replaced. Injector fuel lines again are not a big deal, if you just take care to to allow forein objects to get inside while they are apart. Taking them apart and reinstalling them is not a big deal, but you must leave the injector end open and spin the engine to allow the fuel to refill them from the injector pump, as it takes the high pressure of the injector pump to open the injectors, and air just compresses, and doesn't bleed off the way fuel does. It's called "Bleeding the fuel system" and is REQUIRED whenever the fuel system is opened to the air.
Pete C.'s other suggestions are right in line with my thinking as well.
If you really want to get the BEST understanding of where the enngine is mechanically, you have to to a teardown, or at least pull the head, but that is way more than I would recommend for a running genset that ran a 2 hour full load bank test with no problems. Another option is to send and oil sample to Cummins/Onan for testing, AFTER you have 100 hours of operation on it. They can tell a lot about the mechanical condition of the engine by doing that testing. Prices should be cheaper than a rebuild Gasket Set that a teardown would require anyway. Talk to the Service Mgr at the place you got the shutdown solinoid, about the cost, or even the parts guy should know.
Bruce in alaska
Reply to
Bruce in Alaska
Thanks Bruce, awesome advice. I may actually send an oil sample to Cummins one day.
There was something very unpleasant regarding the solenoid. Cummins sent me a wrong solenoid. When I asked to price me the right solenoid, the price came up to $370 something. I almost had a heart attack.
I found a solenoid 69905K56 at mcmaster.com, it is a 12V, sealed, cylindrical, pull type solenoid with 10 watts (one amp) draw, continuous duty, 80 oz pull, 0.5" rod, 1" pull stroke, 1.5" diameter, 2.4" length solenoid. Vibration proof.
It costs $22.
Since McMaster is 20 minutes from me, I will be at their office tonight to pick it up and will try to adapt it to the engine. I am praying that 10 lbs pull is sufficient and that I could fit it there.
See the bottom of
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look for for "SEALED LINEAR SOLENOIDS"
i
Reply to
Ignoramus23449
I thought that price was awful cheap, I stock that type of solenoid and would expect that you would have had to pay about $170.00. If that $22.00 doesn't work try looking at a Thermo king dealers part # 44-1032. BTW it is used in older TK straight truck units model MDI and XMT. You might check in some truck junk yards . I'll take a look in my used parts inventory tomorrow I think I might have a used one. If you are interested e-mail me. Dave
Reply to
Dave Morrison
: :I found a solenoid 69905K56 at mcmaster.com, it is a 12V, sealed, :cylindrical, pull type solenoid with 10 watts (one amp) draw, :continuous duty, 80 oz pull, 0.5" rod, 1" pull stroke, 1.5" diameter, :2.4" length solenoid. Vibration proof. : :It costs $22. : :Since McMaster is 20 minutes from me, I will be at their office :tonight to pick it up and will try to adapt it to the engine. I am :praying that 10 lbs pull is sufficient and that I could fit it there. : :See the bottom of
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look for for "SEALED :LINEAR SOLENOIDS"
Unless my mental calculation is way off, 80 oz is 5 lbs, not 10 lbs, and according to the chart heading that rating is only for the last 1/8" of stroke, not over the full 1" stroke.
Reply to
Robert Nichols
Bob, you are right. I think that this solenoid will not fit. I will stop by mcmaster and return it. I found something else, item 28-1433 at surpluscenter.com.
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i
Reply to
Ignoramus23449

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