problem with Onan 5500 generator on my 2001 Itasca 35U Suncruiser

I am having a problem with my Onan 5500 generator.  I have a new electric fuel pump, but when I go to start the generator, it starts and then it cuts out like it is starving for gas.  I have checked the fuel pump and it is pumping gas, but cuts out.  Does anybody have an idea what is happening?  The generator was working well, until 2 weeks ago, then I started having this problem.

Check the rubber gas line. It is probably collapsing. You can test with a gas can and gas line into fuel pump.

What's the fuel level in the tank?

3Smdjbss said:

... it starts and then it cuts out like it is starving for gas.

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Does this happen at the moment that you release the START button?

R

I have the same problem so I got an education by reading on the internet and doing some troubleshooting myself.

In my case its was the carb.. I took it off and cleaned it, blew it out with air and used chemtool carb cleaner.. The carb cleaner kind of ruin the gasket on the fuel bowl but I soaked it in oil overnight and managed to put it back together.. After installing the carb I started it and it ran for about 2 minutes which was a improvement as before it didn't start at all.. So I bit the bullet and bought a new one and work fine now.. They say to start the generator at least once  a week with a load on it and run it for at lease 10 minutes.. So I'll do that as carbs are expensive..

The Carb on these units is very prone to gumming and clogging and is un-rebuildable. I tried cleaning it like old carbs yet still didnt work it was to far gone so i replaced it and installed a fuel shut off valve right on the card fuel line which i shut and let it stall itself to drain the carburetor before storage, has worked well so far.

I agree with the Carburetor as I've had to replace mine already and the warranty claim was denied and the reason stated was non-use. I now run my generator on a regular basis. 

Sam! said:

The Carb on these units is very prone to gumming and clogging and is un-rebuildable. I tried cleaning it like old carbs yet still didnt work it was to far gone so i replaced it and installed a fuel shut off valve right on the card fuel line which i shut and let it stall itself to drain the carburetor before storage, has worked well so far.

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Only non rebuildable to some. A fellow has to be use to working on carbs for small engines. I've had very good luck cleaning small carbs, but I've worked on them for over 30 years. Onan carbs are no different, well some of them are made different, but the function is the same. They have very small air and fuel passages, and must be clean to work correctly. Some times the throttle shafts get wore out and then they are cheaper to replace than to repair, but that don't happen often on generators.

92GA said:

 
Only non rebuildable to some. A fellow has to be use to working on carbs for small engines. I've had very good luck cleaning small carbs, but I've worked on them for over 30 years. Onan carbs are no different, well some of them are made different, but the function is the same. They have very small air and fuel passages, and must be clean to work correctly. Some times the throttle shafts get wore out and then they are cheaper to replace than to repair, but that don't happen often on generators.

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Ok guess I should have said it correctly, the factory does not sell a rebuild kit and states these carbs be replaced when needed. I found this to be the best approach for the average Joe. me included since i don't have good carb dipping solution anymore.

Ya just have to know where to buy them. Most of the time ya don't need any parts for just a cleaning. Check this page out. Onan carbs and kits.

http://www.ebay.com/sch/i.html?_sacat=0&_nkw=onan+generator+carburetor&_frs=1

Some carbs are cheaper to replace than rebuild if it needs a throttle shaft kit.

Had exactly the same issue.  Just replaced the carb and now back up and running.  I suppose that taking it off, soaking it, and rebuilding it may work.  There is not much to these things although I read that if you remove the seat adjustment for the altitude, it has to be calibrated.  I just replaced the carb for $240 figuring it was not worth all the time, possible lost money on the rebuild kit, and aggravation.  Adding the shut off valve and running it dry seems to make sense.  There is a drain on the float bowl area but not sure if that would be enough to prevent varnish buildup in those small holes.  Before moving the RV anywhere, I would open the shutoff valve and refill the bowl.  I would think the fuel in the bowl keeps the float from bouncing around and possibly damaging the seats. 

I have the same unit my pace arrow i've also had the same problem check the Altitude adjustment underneath the carburetor sometimes you need to readjust the altitude to fix this problem The carburetor is running to Lynn for the much higher altitude it will give me the same symptoms it is a quick free check

3Smdjbss said:

I am having a problem with my Onan 5500 generator.  I have a new electric fuel pump, but when I go to start the generator, it starts and then it cuts out like it is starving for gas.  I have checked the fuel pump and it is pumping gas, but cuts out.  Does anybody have an idea what is happening?  The generator was working well, until 2 weeks ago, then I started having this problem.

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I just posted this reply in another thread but since it is the same thing, I will repost what I found here....

I had the EXACT same problem and the exact same genset you listed...  and just learned a nice lesson from the guy that came to fix it.. it took him a whole 3 minutes...  On the bottom of the bowl is the screw for the jet pin..  Unscrew it, clean it well, put it back in ALL THE WAY, back it out 1 & 1/2 turns and that's it!  It is possible you will need to do this a couple times to get the gunk out... and you should also spray some cleaner INTO the hole after removing the pin to help remove any left over particles etc..  You also may need to use an emery cloth to clean the jet/pin.. it should be SHINY metal when done.

The genset I have had not run for a few years in this unit as it appears the previous owner was not a maintenance minded person at all.

I played with the damn thing, checked the fuel pump, tried to spray and clean the carb myself ... no luck at all.  Then the tech comes out, unscrews the little screw holding the fuel bowl jet, takes it out, cleans it, puts it back in and the damn thing took right off.

He said this is the problem 99% of the time with Onan units.  He said most people are not aware that these were built and designed for the military and so are VERY high end and reliable.  They even have fully self cleaning brushes unlike civilian and cheaper units that do not.

I start the thing at least once a month now and it takes right off.  I added one can of stabil to my tank as well to help keep it cleaned out since winter is coming..

BTW:  The tech did pull the fuel line and run the fuel pump to verify it worked ok as well.  He said it was recommended if the thing has set for a while because it allows the pump to push any additional crud out of the line instead of into the bowl once the unit starts...  I would suggest doing that as well.. 

One other point for everyone...  If you want to quickly trouble shoot engines, the first thing to do is see if it will even run... The easiest way to do this, which is how I figured out my unit would run but I had no idea how to clean the carb jet thus the reason I had a tech come out, is to shoot some ether into the carb air intake.  If the unit has either a bad fuel pump OR plugged jets, it WILL still start and run and thus you know then it can only be one of two things causing the problem.  IF you spray ether and nothing happens, THEN you have to look at the plugs and coil possibly.

There might be a couple of different carbs used on the Gen.  I've attached two pictures from the one that was on my 2005 unit.  To get to the jet, you actually need to remove the bowl, then you will need a special tool to remove the jet.  Suppose that you could take an old screw driver and grind out the center.  My carb must have been really gummed up because I ran quite a bit of cleaner through it and still did not keep running.  This is 2014 and there is only 32 hours on a 2005 unit, I am sure there was some real gummed up areas.  Thanks for the heads up, certainly would be less expensive to get a driver to remote the jet than replacing the whole carb if it happens again!