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Author Topic: ONAN 11.5 DNAD  (Read 18712 times)

Tom

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Re: ONAN 11.5 DNAD
« Reply #15 on: July 06, 2012, 08:29:02 PM »
The smell is likely unburned fuel which is what the white smoke consisted of. You can test the injector spray pattern on the engine. Just hook up to the fuel line with it pointed in a safe direction, keep hands and body parts away from the spray and crank the engine. You should see a nice fine mist of fuel. If they are similar to my listeroid, they will make a nice metallic clank sound if you can hear it while cranking. All 3 injectors should have an identical spray pattern.
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

ronmar

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Re: ONAN 11.5 DNAD
« Reply #16 on: July 06, 2012, 11:10:43 PM »
I would do exactly what Tom said, with a second emphasis on the safety warnings.  Injection injuries are VERY serious and usually result in some sort of amputation, as it just simply kills the part of the body that gets injected with fuel.  Also breathing the finely atomised fuel is to be avoided at all costs...

You should be able to see a good spray pattery while cranking the engine over.  Yes, with grey smoke the exhaust should smell of unburnt fuel.  Basically the spraypattern is so sparse that the flame front cannot travel fully thru the cloud of atomised fuel, so the heat it makes just further vaporises the fuel and smokes it instead of burning it which creates great white grey smoke.  Great for fogging mosquitos and neighbors, but not so great for making torque:) 

The fact that it ignites at all tells me you probably have sufficient compression.  I can get the same symptom in two ways on my 6/1.  One way is when the hard line is not properly bled.  The injector gives a little series of popping sounds instead of a good solid single click/creak.  This dosn't deliver enough fuel to fire completely untill all the air is bled off the hardline and a full squirt of atomised fuel is delivered.  A poorly firing injector could be delivering insufficient atomised fuel to combust completely....

The second way, particularly when cold, is that the fuel rack is not all the way open. The original listers had a starter pawl on the rack.  You rotated this lever which allowed the rack to open farther for extra fuel when starting.  As soon as the engine came up to speed and the governor closed the rack, this lever rotated and prevented the rack from opening that far when running.

On a mechanical governor, the spring is trying to pull the fuel rack all the way open to the full throttle position.  Once the engine starts, it accelerates till the flyweights come up to sufficient speed and develop enough force to overcome the spring pressure and close the fuel rack.  These two forces balance at the set running RPM.  IF you have a broken spring, there is nothing to pull the rack all the way open for starting/running.  The shutdown mechanism usually adds additional force on the side of the governor to overcome the spring and cutoff the fuel to shutdown the engine.  IF this mechanism is hung up or broken it could be preventing the fuel rack from opening fully.  You say you got it to run sort of, but I bet it would fail to take any kind of load, because it is just barely getting enough fuel to be doing what it is doing.  IF your injectors have a good spray pattern, I would visit the governor and fuel rack linkages... 

PS 6/1 - ST-5.

mauicole

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Re: ONAN 11.5 DNAD
« Reply #17 on: July 07, 2012, 12:43:40 AM »
Tom, Gary and ronmar - thanks so much for taking the time and helping me figure this out! I drained the old fuel and replaced with fresh diesel and some Lucas injector cleaner. It started much as before but this time I ran it for 20 minutes. As time went on there was less smoke. Here is a video of the smokestack at the end of that run:

[youtube]http://www.youtube.com/watch?v=QjUVd0gne_k[/youtube]

After I shut it down I noticed a good amount of fuel had leaked out of the header! Now I beginning to believe it must be the injectors. Next I'll pull them and carefully observe the spray.


1972 Lister SR1
DES 8/1 w/iron piston & 6/1 cam
1983 Ford F250 6.9L Diesel

mauicole

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Re: ONAN 11.5 DNAD
« Reply #18 on: July 07, 2012, 03:18:56 AM »
Here's the test I did. The middle injector in the video didn't spray like the rest, so I switched it with the one on the right and the middle one still didn't work. The spray on each looks pretty good and I made sure the high pressure line wasn't blocked. It looks like I have a bad injector pump.

[youtube]http://www.youtube.com/watch?v=fS-B3xMZRi4&feature=youtu.be[/youtube]
1972 Lister SR1
DES 8/1 w/iron piston & 6/1 cam
1983 Ford F250 6.9L Diesel

dieselgman

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Re: ONAN 11.5 DNAD
« Reply #19 on: July 07, 2012, 03:34:03 AM »
That would be a logical deduction. Check the linkage on the middle pump before replacing it. Also take a look at the cam lobe to be sure that it is providing the full lift it is supposed to.

dieselgman
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations

listard-jp2

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Re: ONAN 11.5 DNAD
« Reply #20 on: July 07, 2012, 10:44:21 AM »
It looks like I have a bad injector pump.

That could be expensive to overcome, as it is not possible to recondition the injector pump on the LP series of engines (due to the pump body forming the element which the pump plunger fits directly into), reconditioning of these pumps is limited to delivery valve replacement, and frankly if you have to replace this item, you may as well replace the whole pump.


ronmar

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Re: ONAN 11.5 DNAD
« Reply #21 on: July 07, 2012, 08:17:02 PM »
Here's the test I did. The middle injector in the video didn't spray like the rest, so I switched it with the one on the right and the middle one still didn't work. The spray on each looks pretty good and I made sure the high pressure line wasn't blocked. It looks like I have a bad injector pump.

Sounds like good solid troubleshooting, looks like you are on your way to an ultimate solution.
PS 6/1 - ST-5.

mauicole

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Re: ONAN 11.5 DNAD
« Reply #22 on: July 11, 2012, 04:52:48 AM »
Finally had some time to do more trouble shooting (big Rodeo this weekend on Maui and my wife likes horses and cowboys) :laugh: The governor linkage has a little fork that controls the pump and feels like it's doing it's job. I checked the cam lift for the middle and rear pumps. The middle one is about .006" less. Doesn't seem like enough to effect the pumps function or does it? Also, if the pump isn't working, why is there so much unburned fuel in the exhaust? (The middle exhaust manifold port was wet with diesel)
1972 Lister SR1
DES 8/1 w/iron piston & 6/1 cam
1983 Ford F250 6.9L Diesel

ronmar

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Re: ONAN 11.5 DNAD
« Reply #23 on: July 12, 2012, 10:26:53 PM »
At running RPM, it may be dribbling a little fuel, but not in a spray pattern that will ignite fully...
PS 6/1 - ST-5.

mauicole

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Re: ONAN 11.5 DNAD
« Reply #24 on: August 02, 2012, 08:07:29 PM »
I pulled the crankcase door to clean and check things out in there and to my horror the middle and rear big end bearings were shot.
Why oh why didn't I check this first? :-\ Both of them could move. The middle was the worst and the journal looks pooched.





 Now I wondering if its worth taking apart to see if the crank and rods are good enough for an overhaul.
1972 Lister SR1
DES 8/1 w/iron piston & 6/1 cam
1983 Ford F250 6.9L Diesel

dieselgman

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Re: ONAN 11.5 DNAD
« Reply #25 on: August 03, 2012, 12:10:52 AM »
Ouch!,

Seems like you would have seen low oil pressure and some extra noise there.

We have conrods available if needed... crankshafts are still available from Lister stocks as far as I am aware.

dieselgman
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations