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Vintage Diesel Onan 17.5kw needs help!


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  #1  
Old 12-10-2008, 10:46:51 PM
Max Diesel Max Diesel is offline
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Default Vintage Diesel Onan 17.5kw needs help!

Hello Smokstak! I need some help getting my dad's stand-by genset running good. The local Cummins/Onan Dealer has worked on it numerous times at a cost of $1500, and it still isn't right. It is a 4cyl Diesel Onan Genset Model/Spec #17.5RD F-3R/17040AA. Serial# F770244808. The problem is, it will run great for 4 minutes, then start smoking a blueish/white, then rev up, and shut of automatically on overspeed. This happens with or without a load.

Cummins/Onan states it needs injectors and maybe a governor assembly, but the parts are no longer available, and the tools to work on it are obsolete as well.

After running it today, I have a gut feeling that the injector pump or fuel pump may be at fault.

Any ideas?? Thanks in advance!!
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Old 12-10-2008, 11:05:48 PM
RSlifkin RSlifkin is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

I'm no diesel expert, but sounds like injector pump to me. If there are a lot of hours, could be rings too. Anything that would cause it to get extra (unwanted) fuel and "run away", tripping the overspeed shutdown.
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Old 12-10-2008, 11:10:28 PM
Max Diesel Max Diesel is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Thanks for the reply! I forgot to mention that it has 752 hours on it. I'm leaning towards the injector pump as well. I'm going to try and get a video of it running in the next few days.
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Old 12-11-2008, 12:32:58 AM
Rodrigue Caron Rodrigue Caron is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Max, Overspeed and blue smoke mean generaly that a product that can burnt enter in the intake and nourrish the engine without control. Remove the crankcase oil cap . Remove the air filter assembly. Remove fuel tank cap. and make a test run. If this fail, test fuel pressure at injection pump fuel inlet. Also make air bubble test at the same place.
Good luck.
Rodrigue
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Old 12-11-2008, 03:09:13 AM
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Question, what is the EXACT Model Number? Could it be 17.5RDJF-3R/17040AA, maybe? If so, then the Injection Pump and the Injectors certainly ARE available, and they all can be REBUILT at ANY quality Diesel Injection Shop. These are VERY common. Lots of Cummins/Onan Distributer Parts Outfit ARE very lazy when it comes to Older Onan Parts. I would find a different Diesel Genset Service Outfit, Pronto..... With Only 750 TOTAL Hours on the Unit, it is hardly BROKEN-In yet.
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Old 12-11-2008, 03:30:24 AM
Raymond Raymond is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

It sounds like the governor ball drive cage is slipping when it warms up. Watch the fuel arm when you start it. It should drop back from full fuel to almost none and stay there without a load change. If it starts creeping up, the governor ball drive cage screws may be sheared or backed out. I've never seen this but have heard of it. If the end cover has ever been off, the governor operating fork may be in backwards. The injection pump and nozzles should be OK or it would never run right. Governor parts can be picked up fairly easily as it is most likely like all the other J engines which there were millions made up through the early 90's. The parts are most likely still available. Sounds like you should stay away from those guys. $1500 is enough to fix damn near anything on that set.
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Old 12-11-2008, 11:37:57 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Would you like me to come up there and give the Cummins guys a few lesson. At 752 hours this things is not even broken in. Parts can be found all over the place and when did hand tools become obsolete. Any good injection shop can rebuild your pump and injectors. One common point for problems was the gasket on the glass bowl on the fuel pump. If it leaks it can suck in air so make sure it is sealing ok. Broken gov spider ring was a problem at one time,but with your low hours I would not think that would be a problem. You might try an eletric fuel pump and bypass the one on the engine. I would also try some cleaner in the fuel. For 1500 I will walk up there and kiss it for you if it will help.
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Old 12-11-2008, 11:41:24 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

As for the hours I have seen them with well over ten thousand hours. Still going strong. I think you may have air getting into the system.
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Old 12-11-2008, 06:26:34 PM
Max Diesel Max Diesel is offline
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Quote:
Originally Posted by Billy J Shafer View Post
Would you like me to come up there and give the Cummins guys a few lesson. At 752 hours this things is not even broken in. Parts can be found all over the place and when did hand tools become obsolete. Any good injection shop can rebuild your pump and injectors. One common point for problems was the gasket on the glass bowl on the fuel pump. If it leaks it can suck in air so make sure it is sealing ok. Broken gov spider ring was a problem at one time,but with your low hours I would not think that would be a problem. You might try an eletric fuel pump and bypass the one on the engine. I would also try some cleaner in the fuel. For 1500 I will walk up there and kiss it for you if it will help.
Now that you mention the fuel bowl, I went out today and checked the fuel bowl. It IS leaking at the fuel bowl. A steady drip from the moment it starts. According to my dad it has been like that, and the service tech actually put a coffee can under it! I will get that fixed and run it again in the next couple days. On the electric fuel pump, what PSI should it be to feed the injector pump?

I wanted to add that when it shuts down on overspeed, it will immediately start back up and run for another 4 minutes. Thanks!
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Old 12-11-2008, 06:35:21 PM
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Default Re: Vintage Diesel Onan 17.5kw needs help!

Fuel return line to the tank clogged or kinked?
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