Onan 5500 run issues

[Weinhofer]

RoyB do you know which fuel pump you purchased from amazon and what the model number is on the front of your generator? thanks

[Jlawles2]

ChadSDunn For over frequency that would be an RPM issue. Probably best left to a certified tech unless you have the necessary equipment to measure the frequency of the voltage out and are familiar with setting the RPM on the generator.

What happens if you load up the generator? I was dealing with a MFG and they had me set the frequency slightly high (62 Hz) so it would sag down but not off the bottom end when fully loaded.

[ChadSDunn]

I have an onan 5500 marquis gold, starts up and run just fine when I have the trail hood of the generator open, but when I shut the lid it randomly dies. But then it will start right back up. I did a maintenance kit on it, Oil,spark plugs, filters. I have plenty of gas. But it’s saying I have code 14? Over frequency. I just don’t know how to fix it or what’s wrong.

[OffToHavasu]

This is why I hate the fuel pump sucking vs pushing. It would take a little work to "mock up" but I wonder how long you could get if you put a fuel pump closer to the tank.

[RoyB]

I just ran the generator under load with the fan blowing under it. It ran for an 1 hour 20 mins before I turned it off. It's pretty warm outside today. Guess I will reach out to GD to see what they say about this situation. I would say based on these 2 tests, something is definitely overheating. Either the fuel is causing vapor-lock, or there's a sensor that's being triggered. I am betting on it not being a sensor since the generator started right back up once I pulled the fuel line and got the air out.

[RoyB]

The exhaust exits the side of the camper. The hot air coming out is from the engine running, not the muffler/exhaust pipe. Gas line stays on curb side and appears to enter near the battery and crosses over in the bay. I didn't get a chance to start it up yesterday. Will try today if it warms up.

[Guest]

While looking over the exhaust is the flame arrestor screen in the end of the exhaust pipe blocked with carbon? If so remove the screen, clean it an re-install it. Look for any kinks or crushed areas that may have occurred. The lack of fuel in the carburetor is a bit of a mystery where in most cases the float will stick open or wear and result in flooding. Rarely does a float stick closed but it can happen.

Jim

[Jlawles2]

RoyB So if I am seeing this correctly, picture left is front of RV (note steps in background). This means the exhaust cover vertically out of the muffler into the small rusted pipe, then it makes a hard turn and runs parallel to the frame. Is this correct thus far? Does the exhaust make another hard turn and exit from under the camper? If the exhaust exit ends under the camper, (spitballing here) is it possible to turn the exhaust 90 so it exits out the side (might try local orange or blue box store) could try ETM or exhaust tubing if the current one is too long so you can trim to length. They sell kits https://www.recpro.com/rv-generator-...RoCs4sQAvD_BwE for helping to keep the heat / fumes from building under the camper (noise also).

Fuel line enters from the curb side (door and steps). Does the fuel line stay exposed down the curb side of the camper? Wondering if it crosses over and is getting heated by the exhaust (especially if it exits under the RV).

[RoyB]

The hot air exits the bottom where the muffler pipe comes out of. The intake is the large rectangular area towards the bottom of the picture. I placed the fan in front of the camper blowing the hot air away from the intake. The fuel lines appear to run along the passenger side of the camper. Opposite of the exhaust pipe.

That's an interesting theory on vaporizing the fuel from heat. I think you might be onto something. There isn't a whole lot of heat shield on the gas lines inside the generator. Takes a little while of sitting before it will start again. This last time once I pulled the fuel line off and broke the vapor lock it started right up. Normally it takes a while to start back up.

[Jlawles2]

The issue with Vapor lock is not always associated with the tank. It could be that the fuel line running to the generator is locate in such a way that it gets warm enough to vaporize the fuel before it reaches the pump. Your fan trick seems to point to a heating issue as you describe. Now to figure out if it's a sensor or the fuel that is getting overheated.

It's hard to tell from the picture, but what way does the exhaust point? Is it pointing out the side of the camper? You could try a piece of ETM to help route it farther or redirect it if it's pointing under the unit vs out the side. Depending on the routing of the fuel supply line, this could also be contributing to the "Vapor lock".

One other thing would be to insulate the bottom of the camper in some way to protect it from the radiant heat from the exhaust. Something similar to https://www.lowes.com/pd/Reflectix-R...5-ft-L/3011906

[RoyB]

I did unscrew the gas cap and it still would not restart. I don't know how long it takes for any type of "vapor lock" to clear up.

[Country Campers]

I think it may be the "vapor lock" condition. I would try the fan routine tomorrow and then turn the fan off to see if it shuts down in 30 minutes again. It may be that the line from the fuel pump to the filter/carburetor may getting hot enough to vaporize the fuel. You could check temps on the line while doing this as well. The interesting part is why would it start doing this at this time? no answer for that.

Brian

[OffToHavasu]

Your findings will be interesting for sure.

I don't have a service manual, so it would be interesting to see where they take the engine temp from and what actual temp vs measured is.

[RoyB]

How odd...And I'm not disputing your finding, just that if that's indeed the case, that to shut down for overheating they shut down fuel instead of just "turning it off". Maybe their thought is if it's over heating it could still "diesel" if there's fuel in the system.

This is a head scratcher.

It's my understanding that the control board shuts the fuel pump off if there are issues. High/low oil, overheat, etc. It's also entirely possibly the pump is still overheating from the hot engine exhaust. Directing the hot air away could help that too. I honestly can't figure it out. In researching, the below have been solutions to other peoples generator running issues:

• Replaced the fuel pump. Even replacing a newly replaced fuel pump
• Replaced the fuel filter
• Replace/clean the carburetor
• Vapor lock
• Air entering gas lines
• Overheating
• Low oil sensor. Add more oil.
• High oil sensor. Remove oil.
• Bad control board
• Loose wire to fuel pump
• Loose 12V power to the generator
• Adjust the altitude knob

[OffToHavasu]

How odd...And I'm not disputing your finding, just that if that's indeed the case, that to shut down for overheating they shut down fuel instead of just "turning it off". Maybe their thought is if it's over heating it could still "diesel" if there's fuel in the system.

This is a head scratcher.