Onan genset trouble code "seven blinks"


John Clark
 

Hi All,

  I case anyone has not seen this before.  Started the Onan 7KW generator after a passage and it turned off shortly after starting.  It gave the seven blinking light trouble code.  My manual indicates this is the “no sea water flow” shutdown.   Don't force the generator to run if you get this code and there is no sea water coming out of the exhaust, like the situation we were in tonight.

 

Checked the obvious sea strainer all good, then broke out tools  to open up the sea water pump and discovered only two vanes left on the impeller.  Installed the onboard ready spare (you should have at least one spare all the time)  but on restart continued to get the no flow shutdown.  Pump was full of water and all vanes aligned correctly.  Checked down stream and found the heat exchanger inlet plugged with …..you guessed it, impeller vanes.   After clearing all the debris and repriming the sea water system the genset is back on line. 

Note, all these steps were rather simple, just a bit tedious.  The pump was easy to open, impeller pulled right out.  New one was a bit of a four letter pushing match to get into the housing but eventually my thumbs won.  The heat exchanger had one bolt to remove the end cap and then used tweezers to pull out the bits of impeller plugging the heat exchanger.    Will post pictures on the FB page. 

 

Take home message, onboard spares, and “yes you can do it yourself with a little patience and common sense.  This repair cost us one impeller, ($30USD)  and 1.5hr labor.  How much would an Onan technician charge us for this repair?  

 

                   Regards,  John

 

John Clark

SV Annie  SM 37

Just moored at St.  Augustine for Christmas



rossirossix4
 

Hi John!
If you put a zip tie around the impeller and tighten it it makes it pretty easy to insert the impeller.  Start with the zip tie toward the end you are inserting.The zip tie slides off as the impeller is inserted.  We apply some Lanocote on the metal spindle as well and use silicone grease or the Jabsco grease on the impeller. We keep a zip tie in our kit.  They can be released with a jewler screw driver and re-used.

Related--we are big fans of the Impeller Puller sold by BayShore Marine in Bert Jabins Yacht Yard in Annapolis.  We use a rag over the edge of the raw water pump if any prying is applied.  http://bayshoremarineengines.com/impellerpuller.aspx They are also our very favorite for any Yanmar or Onan parts. 

Whenever our generator is not in use (even at anchor now due to solar panels) we close the seacock and run fresh water into the sea chest and through the Onan cooling loop.  We also do this with the AC pumps, anchor wash, toilets, Dessalator feed pump,and Yanmar (and the corrosion prone manifold in the process) whenever we can--especially after docking but it is also easy to do at anchor or even underway.  

Fresh water helps disolve deposits and salt, decreases galvanic action, and helps eliminate marine growth.  We also think that the dried out salt crystals and deposits on the above-water-line Onan raw water pump contributes to the short life of Onan impellers.  When we begin to desalinate water we usually divert (using a 3 way valve attached to a short hose) the first 3-4 gallons into jugs stored on the floor of our engine room. The TDS usually diminishes during this period and any odor would be reduced plus we have a chance to manually test the water with a TDS meter and observe for any desalination system drips.  This becomes the water we use to flush the generator when we are done using it.  We almost always make fresh water when using the generator.

Bob and Suzanne, KAIMI SM 429
 


John Clark
 

Hi All, 
  First thanks for all the advice, Especially Bill, Eric, Porter, Thomas,Mark, and Bob, you all are great!

  We have everything back on line now.  Will post some pics to FB later.  

Bill:  You are right as usual except, as you pointed out during my purchasing process when I sent you some photos (which you helped me with a lot, and I am indebted...) that the genset and engine were NOT original.  They were replaced by Amel in 2003 with the newer versions.  So yes I have the "no SW flow" sensor that Eric speaks of and yes Eric, I did remove it and clean out the port.  It think the post impeller change no SW flow was however caused by the 14 impeller vanes clogging the heat exchanger down stream.   My heat exchanger has an end cap with one bolt making it easy to remove and inspect...and pull vanes from :)

I think the previous owner changed the impeller. some time in the past..and left some vane-debris in the flow path, I found fourteen vanes in the heat exchanger.  The new impeller has twelve....hmmm

Anyway, we were "down" for less than one hour...mostly thanks to having the right onboard spares...and Capt. Mcguver.

  Regards,  John

John Clark
SV Annie  SM 37
Moored (finally) in St.  Augustine Florida for Christmas.