Onan problem

[John Hennessey]

Our diesel generator in our boat used to run for a minute it two or even 15 minutes or so and then quit  it turned out we had air in the fuel line. So every year when we put the boat back into the water we would bleed the line at the lift pump. At first we didn't know what the problem was and we burned out the lift pump. Diesel generators a famous for air in fuel problems  make sure your tank is full when you store it and bleed the fuel line

[David T. Richelderfer]

Yes... it's a 3-way switch that is spring loaded to rest in the middle position (its off position).  Pushing and holding the rocking switch in the down position accomplishes the priming operation.  Hold it in the down position for at least one minute.  If everything is off and quiet, then you can hear the fuel pump working.  Then push and hold the rocking switch to the up position to start the generator.  With my generator, I thought pushing it to the up position actuated glow plugs initially because there was a several second delay before the generator starter motor turned over and started the engine.

The rocking switch in my coach is located on the left dash just under the Kenwood.  I have 5 switches there lined up horizontally.  From left to right the 5 switches are DRIVING LIGHTS, DOCK LTS, START BOOST, GEN START, and ATC.  The GEN START switch has a horizontal light bar built into its lower half, I assume, to signify you have actuated it.

[Edward Buker]

Dave,

Do you get a code when it shuts down? Is it very abrupt like you would get when you press the stop switch? Your genset is at an age where one would expect the cooling fan belt to have streched and aged. Hours do not matter so much here with this issue. I characterized my genset using an IR gun with the failing belt and with the new belt. From an earlier post....

On my genset with a good belt I read 118F on the radiator face, 144F on the oil pan, and 187F high on the block. Your numbers will vary some from mine but they should be somewhat close. With a slipping belt my radiator reached 216F, oil pan 207F, and the block was 215F. You will not hear any squeal from a slipping belt in this application.

I'm not saying this is your issue but the length of run time before shut down is about right as is the age of your belt. This problem is easy to sort out with an IR gun and the numbers listed above. BTW running with the front cover open for more than a minute or so should be avoided given the enclosure is required to move air through the radiator for cooling.

Later Ed

[Dave Cunningham]

Hmmm, I am going to try that, a diesel mechanic I talked to today said it sounded like I have air in the fuel line.

[Dave Cunningham]

David/Ed,
For some reason didn't see your post before my last reply, thanks for those ideas, I am going to get right into this thing in the next few days, I was busy all weekend finishing all the paint repairs at my shop, and other than the ice maker, that hasn't arrived yet, thagenerator is my last issue( unless something else broke since I drove it home this afternoon)

Dave

[Edward Buker]

If you suspect air in the system usually the diagnostic tool is a sight glass worked into the fuel line on the engine side of the filters etc. If you see air passing through with the fuel you can then tighten fittings, change filters etc until the air source is found and resolved. Air leaks would tend to make it not start. Your running 15 minutes and dieing would seem to not fit well for an air leak. I'm not sure of that, just a guess. If air was getting in it would seem that the engine would run rough as it dies. If it is an overheat or some parameter the computer system monitors for, when the safety systems shut the engine down it would be like hitting the stop switch with a sharp cut off. Usually a code is transmitted with that type shut down. This site has sight glass fittings available.

https://secure.k9bytes.net/~monacoto/cgi-bin/k9bytes.pl?command=listitems&pos=0&type=search&search=cummfsy

Later Ed

[John Hennessey]

Ed I disagree. The first thing the mechanic said when I told him the issue with our generator was air in the line there are so many places for it to come in including a microscopic hole in the line itself including all the fittings. Once we started keeping the tank full and bleeding the line at the lift pump we solved the problem

[Richard And Babs Ames]

Have you looked at the switch on the generator itself to see if it is showing a fault code? The codes do not show on the remote start switch on our Onan.

[Dave Cunningham]

As I mentioned in the first post, it does show a 13 code, when you first try to start it, but I did not check for a code after it died the last time , I will have to check that

[Edward Buker]

John,

As I think about it, if there was an air leak it would allow the fuel line to drain back to the tank, therefor the hard starting and the need to prerun the pump. I'm not sure you would get it to start and die 15 minutes later with an air leak unless the small filter held enough fuel for a 15 minute run. For my generator I never pre run the pump and even a month later it goes through the start sequence, does its short delay preheat, starts the fuel pump and then just fires up. I have never had to do anything special. I think that assures that I do not have any air leak....

 I guess the only way for Dave to know for sure is a sight glass. I had my older Beaver die one day and had to get towed into a a Cat dealer in Denver and they installed a sight glass at the engine fuel inlet and saw air in the fuel stream. We worked it back to the line from the tank and saw no air in the fuel stream. The secondary filter gasket was leaking and ended up being a Cat Part defect. They treated me kindly given that. It had gotten cold and the gasket was already marginal in a compromise location on the filter interface to the housing. Cat bean counters had them redesign three PN filter designs into one offering which turned out to be the bad compromise unit for me. The original filter had two well spaced O rings and the new PN had one that lined up right at edge of the flat gasket face on the housing.....upsetting when the bean counters are in charge.

The sight glass is the definitive way to rule this issue out or to diagnose the problem source but it does have to be plumbed in to use it.

Later Ed

[John Hennessey]

The other issue it could be is with the lift pump overheating as a result of air in the line.  Ours ran for 15 minutes and then quit just like Dave's.  There should be a bleed screw on the lift pump.  It's easy to bleed by yourself.  If that doesn't solve it have the lift pump tested.  We found that we had overheated it and killed it before we found the air leak.

[Dave Cunningham]

I am waiting for a call today from Cummins in Vancouver , they are trying to help me out since I spent all that money on the board there, they have one of thier rv guys looking at the problem, I am going to gather his suggestions , combine them with the ones you guys have given me , and see if I can figure this thing out.
John, I am assuming the lift pump is part of the generator itself? is it easy to get at?

[Glenn Perkins]

Dave,

We have over 3000 hrs on our 10KW unit (many summers of nothing but dry camping near the Grand Canyon) and have experienced similar smoking and shutdown issues.  We found that Ken Vick at the Rocky Mountain Cummins shop in Albuquerque NM was a virtual whiz at troubleshooting and resolving our issues over the years.  A couple times, when this issue reappeared, Ken was able to diagnose a restriction in the fresh air intake system ... due to dry camping on our wilderness property, wood rats and field mice had been "sucked" into the intake.  Upon "exhuming" the dessicated carcasses, the generator returned to good operating condition.

If your travels ever take you to Albuquerque (maybe for the Baloon FIesta??) and you are still seeing the problem, give the shop a chance ... their number is (505) 247-2441.

Good luck and safe travels.
Glenn

[Dave Cunningham]

Thanks, Glen!

[Dave Cunningham]

Just had a tech from Cummins spend 2.5 hours trying to diagnose the generator issue, I had it all set up for him to work on and the first thing he did was pull the air cleaner element, on the initial startup it fired , pumped out a bit of smoke for about 3 seconds and ran perfectly, I know your thinking " Dave , I thought you said you just had it serviced by beaver coach in Bend, " which I did, apparently changing the air filter is not part of the service . the other problem that he detected is that I am only getting about 9 volts to the unit on startup, ( it has always cranked a little slow ) and he said that there are relays on the board too control the glow plugs , controller ect. that need good voltage to engage, checked all the connections at the unit and they all seem fine, I need to see how the positive lead is routed to the batteries and find out why there is a voltage drop, but it seems like the air cleaner was playing a big part in the situation. So after a $1000.00 control board and $ 450.00 in mobile service charges, I will replace the $ 30.00 air cleaner and see what happens.

Dave