Onan 5500 not starting...partially solved

[danemayer]

A couple of things to try next time you fire up the genny - in case you have a problem after the generator.

Just turn on one of the generator circuit breakers. Then experiment with running appliances. Half of the circuit breakers will be powered, so expect that not everything will work.

Then turn that breaker off and switch the other one ON. Test appliances again.

With both breakers on, before turning on the Air Conditioner, take some voltage readings around the coach to see if you have 120V between HOT and Ground and also between HOT and NEUTRAL pins on the outlets. Check NEUTRAL to GROUND to make sure it's very close to zero volts.

Keep reading voltage as you turn on the A/C unit to see if it changes.

 

[NWILSON]

With the generator off and shore power disconnected (NO 110V available to the rig) check the wire connections at the circuit breakers on the generator. If at all possible, check the other ends of the generator wires at the Transfer Switch. Loose connections can cause crazy things also!

 

[Ladiver]

Looks like I get to clean out my storage area! That is the only way I am getting to the transfer switch. I am not a very big guy at all (5'7 180), but that sure is a uncomfortable location to get to.

Dan, that was going to be my next test. I will test and report back. This time, I will bring the camera and get some video too.

 

[Jim.Allison]

Don't buy the carb yet, I have more on this subject, it looks like I may have stumbled onto some information for you, I just don't have time to relay it to you. The onan is VERY sensitive to some environments. That Is why "exercising your generator is so important, Its not your fuel, its something else and I will get that info for you, including the fix. It beats buying a carb and finding out you did not need it. I will be back with specifics tonight. Meanwhile check your governor, and your auto gen start. The 36 code could be that your started the generator manually and the auto gen start shut it down. The 36 code means that the generator shut down differently than it was started. ie manually vs auto vs dying. Do those two things and I will get back on the minor corrosion problem that may be causing the whole problem.

Jim.Allison, I do have an auto-gen start installed. I have not checked the governor Unfortunately, a mechanic I am not, and did not go beyond the carb yet. But after this, I may be a little more qualified than some of the local shops around here. You also mentioned something about salty air. I did spend 4 days last year camping at the beach, but that is the only time I was exposed tot he sea breeze. I did a visual on everything and did not see anything that appeared to be rusty or corroded. Is there anything specific I should look at?

They symptoms are that the generator starts fine with the breakers off. I let it idle for a minute or so, then flip the 2 breakers on. Everything still is OK. I go into the trailer and can hear the converter activate and supply generator power to the rig. At that time, I can view my inverter controller and see that the batteries are charging and the amps that are being delivered. I do see the "surge" of amperage (+/- 10-15 amps). The lights visibly dim during the surge, but the generator sounds the same. I can power on the main fan and hear the surge while it is running. When I turn on the air conditioner, it runs for a few second and surges. That is then the converter kicks the generator power off. Keep in mind the generator is still running and no error codes are being produced. Unfortunately, I have not tried another load yet. Maybe tonight or this weekend.

Duane, I tried rapping the solenoid, but that did not work. Then I tried beating it. Still nothing. Next step would be a .45 to it! I did see that I can buy a replacement. That means I can remove it and try to manually force the plunger.

Neale, as you said, it would be better with video. I thought about that after I removed the carb for the last time last night. I am half tempted not to clean it up today, but reassemble and video everything. After reading Jim.Allison's comments, I bet cleaning it even more will not do much. Either way, I will get the GoPro set up to film the re-installation of the carb and the future testing.

Thanks,

Jeff

 

[Ladiver]

OK, we tore apart the carb in the lab this morning. The thing was clean. The solenoid plunger was not gummed up at all. It moved back and forth fairly easily. We then looked at the altitude adjustment that too looked clean. As we went part by part, we came to the tube that runs up the middle of the carb.

We removed that and the outside looked good, but we could not see through it. There was something blocking the light. So, we blew it out with compressed air and now can see the light. We continued to check each piece of the carb and found NOTHING that would say it is a problem with the carburetor. After clearing that one tube, we reassembled everything and I am going to give it a try this afternoon.

I now understand how the carburetor works and completely understand that this clogged tube could be the source of problems. But, I will have to check and see. If it is, the fix was not too difficult. If it is not, then to start looking at other items. I will keep you all posted.

Thanks,

Jeff

 

[Ladiver]

Don't buy the carb yet, I have more on this subject, it looks like I may have stumbled onto some information for you, I just don't have time to relay it to you. The onan is VERY sensitive to some environments. That Is why "exercising your generator is so important, Its not your fuel, its something else and I will get that info for you, including the fix. It beats buying a carb and finding out you did not need it. I will be back with specifics tonight. Meanwhile check your governor, and your auto gen start. The 36 code could be that your started the generator manually and the auto gen start shut it down. The 36 code means that the generator shut down differently than it was started. ie manually vs auto vs dying. Do those two things and I will get back on the minor corrosion problem that may be causing the whole problem.

Thank Jim, I look forward to any additional information. No rush, any time this weekend is fine. I am not going to buy a carb just yet. After cleaning it up, I will try that. Plus I will check the other items.

 

[porthole]

Without physically seeing it, I'm guessing the tube you are referring to is the bowl vent or balance tube. If the vent is clogged the fuel bowl may not maintain the correct level or allow the fuel to be pushed through the jets.

Carburetors work on a pressure differential. So the fuel bowl needs to be vented to the atmosphere. It is the differential of pressure from atmospheric (inside the air intake system) and the lower pressure caused by the carb's "venturi" effect at the throttle blade/s that pushes fuel through the jets into the throttle bore to be mixed with air. If you looked closely at the throttle bore you would see that the bore narrows where the blade pivots. With the engine running and air being pushed into the throttle bore that narrow section creates a venturi - low pressure. Looking closely in that area you probably would have seen something that allows the fuel into the bore, maybe a small tube or maybe just small slits on the side of the bore.

Although carbs are relatively simple, there are multiple things going on from no run to idle to mid throttle to full throttle, then add in acceleration and decel. There could be several small passages and jets and tubes like you found that can clog easily.


Since you found something in what may be one of the very important passages in the carb, you may have solved your issue.

BTW, code 3-6 is a catch all code for our gennys. The simple answer is run speed and voltage are not correct, so the code is set. With the genny running poorly and hunting up and down trying to maintain speed, low voltage output or engine speed issues are an easy target.

It certainly doesn't help that the units are set to just barely run at the leanest mixture that still allows operation with minimal emissions. Couple that with sealed carbs that don't allow adjustments and now, the lack of overhaul - service kits, and we get the operational issues similar to what you have now.

How simple things could be if we still had idle screws that could be removed, spray some carb cleaner in the hole, reinstall, set the mixture and have a smooth running engine.

 

[Jim.Allison]

This might hold some answers for you, I providing an excerpt from this PDF. Then the link to the site and a link to the PDF. At the end of the PDF is a guide for information off your Onan that will be handy when doing troubleshooting. This PDF also has a lot of testing that you can do with a multimeter. I don't know how easy it is to remove and bench your generator, but if it is like mine, I would do anything before I thought about taking it out for visual. So I think the multimeter test a good thing.

Excerpt from PDF

Q. What are slip rings, where are they located and what is their function?

A. Slip rings are two flat metal rings located side by side on the rear of the rotor (end away from the engine) that providea means of contact for the brushes. The brushes run against the slip rings and carry the current (field current)required for magnetizing the rotor.

Q. Why do the generator’s slip rings require cleaning periodically?

A. During periods of storage and a lack of regular exercise, RV generator slip rings can become corroded, particularlyin areas near salt water. Even with regular running, a layer of oxide and brush residue can build up on the rings, increasingtheir electrical resistance. Proper cleaning (such as with the Slick Stick Slip Ring Cleaning Tool, availablefrom Flight Systems) restores the running surface to like-new condition. This results in cooler running as well as extendedbrush and regulator life. Dirty slip rings can cause overheating and premature regulator failure.

Q. How can I determine if the slip rings need to be cleaned?

A. A quick visual inspection can be done by looking through the cooling slots at the rear of the generator with a brightlight. The slip rings should appear as shiny clean metal. You can also unplug the regulator and measure the resistancebetween pins 9 and 10 of the plug that was connected to the regulator. If this reading is greater than 28 ohms, cleaningis needed.


Here is the link to the PDF

http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf

Link to the site

http://www.flightsystems.com/troubleshooting/

 

[szewczyk_john]

Now that you had it apart can it be rebuilt and reassembled for use?

 

[Ladiver]

Now that you had it apart can it be rebuilt and reassembled for use?

John,

Short answer, yes. Long answer is be very careful when disassembling. There are no parts kits, so if a seal is damaged, you get to buy a whole new carb.

 

[Ladiver]

This might hold some answers for you, I providing an excerpt from this PDF. Then the link to the site and a link to the PDF. At the end of the PDF is a guide for information off your Onan that will be handy when doing troubleshooting. This PDF also has a lot of testing that you can do with a multimeter. I don't know how easy it is to remove and bench your generator, but if it is like mine, I would do anything before I thought about taking it out for visual. So I think the multimeter test a good thing.

Excerpt from PDF

Q. What are slip rings, where are they located and what is their function?

A. Slip rings are two flat metal rings located side by side on the rear of the rotor (end away from the engine) that providea means of contact for the brushes. The brushes run against the slip rings and carry the current (field current)required for magnetizing the rotor.

Q. Why do the generator’s slip rings require cleaning periodically?

A. During periods of storage and a lack of regular exercise, RV generator slip rings can become corroded, particularlyin areas near salt water. Even with regular running, a layer of oxide and brush residue can build up on the rings, increasingtheir electrical resistance. Proper cleaning (such as with the Slick Stick Slip Ring Cleaning Tool, availablefrom Flight Systems) restores the running surface to like-new condition. This results in cooler running as well as extendedbrush and regulator life. Dirty slip rings can cause overheating and premature regulator failure.

Q. How can I determine if the slip rings need to be cleaned?

A. A quick visual inspection can be done by looking through the cooling slots at the rear of the generator with a brightlight. The slip rings should appear as shiny clean metal. You can also unplug the regulator and measure the resistancebetween pins 9 and 10 of the plug that was connected to the regulator. If this reading is greater than 28 ohms, cleaningis needed.


Here is the link to the PDF

http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf

Link to the site

http://www.flightsystems.com/troubleshooting/

Thanks Jim. I will definitively take a look at that. I am getting ready to go back out and install the carb and see if the cleanup worked. If not, I will follow the PDF you linked too.

I need to get my make-up on and mount the GoPro. I will hopefully have a video posted showing the genny working just fine. I might as well do one for the removal and reinstall of the carb.

 

[porthole]

Reading through all this gives me another idea for the next time mine gets a little snarky running.

Years ago when carbs still had adjustments and the onset of cat converters, one of the set procedures we would use was a "propane enrichment" adjustment. Simply put, we injected propane into the carb and adjusted the mixture and idle rpm based on the rpm change.

An advantage to this tool aside from setting mixture is that it can be used to find intake leaks, make vehicles that barely run due to a lean mixture run well enough to get into the shop and to get engines running after fuel system service when it took a long time to draw fuel through the lines. Open the valve far enough and a V-8 will run on straight propane before the pump gets fuel into the carb.


I still have my "Miller special tool". I'll have to pack mine in the trailer when the spring get ready takes places, have it on hand to check my genny when it acts up.

 

[Ladiver]

A couple of things to try next time you fire up the genny - in case you have a problem after the generator.

Just turn on one of the generator circuit breakers. Then experiment with running appliances. Half of the circuit breakers will be powered, so expect that not everything will work.

Then turn that breaker off and switch the other one ON. Test appliances again.

With both breakers on, before turning on the Air Conditioner, take some voltage readings around the coach to see if you have 120V between HOT and Ground and also between HOT and NEUTRAL pins on the outlets. Check NEUTRAL to GROUND to make sure it's very close to zero volts.

Keep reading voltage as you turn on the A/C unit to see if it changes.

OK, videos are being processed right now. I still have the problem with the power fluctuating. I checked the voltages with nothing running and I am seeing 117.8-118.1. This is not quite the 120 that I thought it should be at. Also from neutral to ground, I see 0.0-0.1. Good enough for me. I am going to retest later and take readings when air is running.

I am waiting for the genny to cool down and I will start working on Jim's suggestions. Of course I will also get video of that process too.

 

[Ladiver]

Sorry about the audio quality. I guess I need a little practice with the GoPro. Not too bad, considering it is in a waterproof housing!

First video has been uploaded to YouTube, "Onan 5500 Carburetor Removal".

Second video "Onan 5500 Carburetor Installation"

Third video "Onan 5500 Startup After Carburetor Installation"

 

[Jim.Allison]

Bravo, Bravo. I loved the video, I'm not scared of that boogyman anymore. LOL. And I learned something.

 

[Ladiver]

"Onan 5500 Surge and Rattle"

"View of Magnum Controller During Generator Surge" No load

"View of Magnum Controller During Generator Surge" Air Conditioner is running

 

[Ladiver]

Bravo, Bravo. I loved the video, I'm not scared of that boogyman anymore. LOL. And I learned something.

Yes, the boogeyman has been tamed. There are some things that you just have to be willing do and learn while doing. Glad I could help. I hope others can watch these videos and learn something too.

Maybe Duane can start posting some videos too. ;-)

 

[NWILSON]

Jeff,
The rattle you are hearing is the fuel pump sucking air!

 

[Ladiver]

Jeff,
The rattle you are hearing is the fuel pump sucking air!

I suppose that makes sense. What was not shown in the video is that I had disconnected the fuel tank and was running off a gas can. I did this to confirm it was not bad fuel. It very well could have been sucking air, I was not monitoring the gas can and the tube inserted into it.

 

[Ladiver]

This might hold some answers for you, I providing an excerpt from this PDF. Then the link to the site and a link to the PDF. At the end of the PDF is a guide for information off your Onan that will be handy when doing troubleshooting. This PDF also has a lot of testing that you can do with a multimeter. I don't know how easy it is to remove and bench your generator, but if it is like mine, I would do anything before I thought about taking it out for visual. So I think the multimeter test a good thing.

Excerpt from PDF

Q. What are slip rings, where are they located and what is their function?

A. Slip rings are two flat metal rings located side by side on the rear of the rotor (end away from the engine) that providea means of contact for the brushes. The brushes run against the slip rings and carry the current (field current)required for magnetizing the rotor.

Q. Why do the generator’s slip rings require cleaning periodically?

A. During periods of storage and a lack of regular exercise, RV generator slip rings can become corroded, particularlyin areas near salt water. Even with regular running, a layer of oxide and brush residue can build up on the rings, increasingtheir electrical resistance. Proper cleaning (such as with the Slick Stick Slip Ring Cleaning Tool, availablefrom Flight Systems) restores the running surface to like-new condition. This results in cooler running as well as extendedbrush and regulator life. Dirty slip rings can cause overheating and premature regulator failure.

Q. How can I determine if the slip rings need to be cleaned?

A. A quick visual inspection can be done by looking through the cooling slots at the rear of the generator with a brightlight. The slip rings should appear as shiny clean metal. You can also unplug the regulator and measure the resistancebetween pins 9 and 10 of the plug that was connected to the regulator. If this reading is greater than 28 ohms, cleaningis needed.


Here is the link to the PDF

http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf

Link to the site

http://www.flightsystems.com/troubleshooting/

Jim,

I tried following that procedure and without getting the entire genny out of the box, I just don't think I will be able to get to the slip rings. I did shine a light in the cooling vents and it looks ok to me, but I could only see a very small section inside.

I disconnected my auto gen start to make sure that was not the problem.

Current situation...Generator starts fine and idles fine with breakers off. When breakers are turned on, it runs well for a while. It does seem to run better since cleaning the carb, but it still surges when there is a heavy load, like the a/c or microwave. I tested with one breaker at a time, then both. Surging occurs in all three positions.

Voltage at an outlet dropped from 117.9 to 114 when the a/c fan turned on.

Here is a video (crappy cell phone) of the Magnum controller display showing a pretty steady supply of power, then the surging and shutdown of power.

Next up is empty out the under storage and check the transfer switch and converter.