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Socaltoolguy · 06-30-2015, 11:48 PM

It was suggested that I move my original thread to this forum. So, here it is.

I have a Onan 5500 Marquis Gold that has less than 330 hours on it. I let it sit for a while without running and now I have a problem. It starts with starting fluid, runs for a minute or two then shuts down. It won't restart without the starting fluid. I am getting a 3 6 code. I figure the carb is probably gummed up but I hate to buy a new carb without knowing for sure that is what is the problem. Can anybody enlighten me? The fuel pump seems to be pumping ok. I can here it during the priming operation. It ran long enough to get warmed up and then the governor started bouncing up and down and finally shut itself down. Does it sound like carb time or is there some magic chemical that I can run through it? I know the Onan 4C is no longer available and the Amsoil carb foam is not available in Cal. Help!!!

Ray

LarryH1481 · 07-01-2015, 01:27 AM

https://www.youtube.com/watch?v=CLLI359w2RM

I would try to get the varnish cleaned out of the carb. The link is a good tutorial on Onan 5500 carb issue. I'm in CA also, did not know about the Onan 4c ban. Maybe Onan can help with alternative. Good luck!

Socaltoolguy · 07-01-2015, 12:31 PM

Thanks Larry, I did watch that video the other day and got a lot of good info from it. The Onan 4 C is discontinued by Onan and someone else suggested the Amsoil carb foam but it's the one that is banned in Calif. I contacted an Amsoil dealer close to me who was going to try to get some from a friend but I have not heard back from him yet. Thanks again for your post. Yesterday, I did get it running using starting fluid and it ran for a good 5 minutes. I then tried to load it by turning on one of the rooftop a/c's. It ran for a minute and then shut down. It's definitely a fuel related problem. I am going to check the fuel line running from the tank to the genny. I am also going to do the filter/pump test as this video showed. I do believe it's the carb being gummed up though. I just hate to replace it just because it's dirty. There has to be some chemical available that will flush it out. Years ago, the tune up guy at the shop where I worked would run a product by the name of Berrymans through carbs to clean them out and also to lubricate the upper end of the valve train. It made a terrible cloud throughout the shop so it has probably been banned too. We have nice clean air here but sometimes, maybe it's too clean. Politically speaking that is.

Ray

mavric65 · 07-01-2015, 12:36 PM

Does the fuel pump run when you prime the genset I had similar problem and my code was 36 and a fuel pump was the problem. I got a replacement from Amazon for under $40

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Socaltoolguy · 07-01-2015, 01:28 PM

Pump runs and it primes. At least I can hear it run. And it seems that I can see the fuel line "jump" when I push the prime button. The funny part is, if I let it set for a while and then prime it, it will start. But once it shuts itself off, I have to wait for a while before trying it again. If I try to restart it right after it shuts down, it won't fire. But, if I spray starting fluid in it, it will fire off but quit again. So, it seems to be running out of gas. I'm wondering if maybe I have a fuel filter that is not clogged but is sort of clogged. Or a delivery hose that is partially clogged.

Ray

LarryH1481 · 07-01-2015, 04:35 PM

OK...I've read lots of reports of Onan 5500 shutting down when heats up. Most of corrective action was replace fuel pump! When elect fuel pump heats up it fails, after cool down, it works gain. I would replace fuel pump and fuel filter! I use Berryman B12 for my chevy carb/fuel injection cleaner. Gets great reviews and auto store available. Good luck.

Socaltoolguy · 07-01-2015, 05:18 PM

Thanks again Larry. I'm leaning that direction too. But, I want to try the pump test first. What should I have to pay for a new pump. I did see some on Amazon for around $50. Does that sound about right?

R

LarryH1481 · 07-01-2015, 05:54 PM

Onan OEM fuel pump runs from $85-100, which is more than I want to pay. Amazon Onan direct replacement brand in the $50 range. Airtex is a popular brand (I use them in my Chevy truck). I may need this in my RV some day and I would go this route. Also change the fuel filter into the Fuel Pump, prevents particles from fuel tank entering Fuel Pump.
Onan had bad fuel pumps & recall where the internal rubber of fuel pump would expand with heat and block the fuel flow. Fluctuating RPM of GenSet would cause it to shut down (code 36). This may be the problem your experiencing. Go with the Airtex brand. Verify your fuel pump P/N.

Robot Check

Vacationer49 · 07-01-2015, 07:22 PM

Use sea foam in the carb. Open the air breather up and put a little in at a time allowing the engine to bog down but not die. Do this 5 or so times, it will create a ton of white smoke out of the exhaust. After you finish the above instructions, pour the sea foam in to the point it flood the engine and it dies. Allow to sit for 20-30 minutes and fire it up. It will again pour white smoke out of the exhaust for a few minutes but it will clear up. If you still have trouble I would maybe do a second application but after that I would start looking at another culprit such as fuel pump.

mavric65 · 07-01-2015, 07:43 PM

Quote:

Originally Posted by Socaltoolguy

Pump runs and it primes. At least I can hear it run. And it seems that I can see the fuel line "jump" when I push the prime button. The funny part is, if I let it set for a while and then prime it, it will start. But once it shuts itself off, I have to wait for a while before trying it again. If I try to restart it right after it shuts down, it won't fire. But, if I spray starting fluid in it, it will fire off but quit again. So, it seems to be running out of gas. I'm wondering if maybe I have a fuel filter that is not clogged but is sort of clogged. Or a delivery hose that is partially clogged.

Ray

Socaltoolguy just a heads up if you change the fuel filter you might have 2 on your genset 1 before the pump and one on the carb. There is a fuel filter delete for the carb filter because they had problems with the one on the carb leaking and there is no need for one after the pump . onan has a fitting that goes on the carb that is the same length as the filter so the hose fits. HERE IS THE PART # cummins A026E529 onan replacement fitting I picked one up from onan but had to give them the part number since they had no clue what I was talking about ..

Socaltoolguy · 07-03-2015, 02:55 PM

Thanks to all of you for your kindness and info. I tried running it again yesterday. I primed it for at least 20 seconds and it fired up and ran until it ran out of the prime gas. I am going to have to do some more checking. I'm going to replace the fuel hose, filters and pump as I do my testing. Luckily, I have some time before we hit the road again.

Ray

Socaltoolguy · 07-07-2015, 12:59 PM

I've located some of the Amsoil carb foam so I'm asking for advice on using it. Have any of you used it and if so, what is the best way? I'm assuming that I should drain the carb and disconnect the fuel line, squirt the foam in through the fuel inlet and reconnect the fuel line. Am I on the right track? How long should I let it sit prior to restarting the engine? Once it's running, what's next? I know these may sound like silly questions but I don't want to have to do this more than once. I have reconciled myself to having to buy a new carb/fuel pump/fuel filters so I hope this at least helps to put those purchases on hold. Thanks for all you help folks,

Ray