Cummins Onan 5500 Generator

dieseldan723 wrote:
OK, this is weird. I went out this morning. Pushed the PRIME button and tried to start it. It did not start. I went out and took the cover off and there was gas everywhere. It wasn't quite dripping out the bottom but there was a layer of gas on everything. I could wipe it up with my hand. As I said earlier, it really smelled like gas, now I know why. I went back into the trailer and the gas gauge showed EMPTY!

The last time I looked it was at 3/4 full.

I am concerned the gas gauge is not working properly. In hindsight it does seem weird to me that I could run the generator for nearly 7 hours AND fill the quad once (5 gallons) and still have 3/4 of a tank. I did move the trailer this weekend and maybe that caused the sensor in the tank to become "unstuck". There is no way it could go from 3/4 to empty just sitting there unless 1)there is a leak 2) someone is stealing my gas - the trailer is behind a locked fence 3) the gas gauge is not working, or a combination of the above.

My guess is that it won’t run because it is actually out of fuel but I don’t want to put more in if there is a leak. I probably should take it in as it’s still under warranty.

Been following your thread... timo

As Thunderbolt said, carb needle and seat probably are leaking/sticking from being gummed up. Probably an easy fix, but more than likely, the rest of the carb is not metering fuel correctly either. And with staked in jets,tiny tiny af passage ways, no gaskets or parts available, a getto parts-less rebuild is not a solution for most.

IMO, best way for you to go now, bite the bullet and spend the $169 for a new carb. And always run the max ratio amount of stabilizer, STA-BIL or SeaFoam in your fuel. And still run it once a month. Might get away with once every 3 months with max fuel stabilizer, but don't push it.
Some say drain the float bowl after every use before storage. This might work/help also, but might also dry out gaskets/orings and also cause leaks eventually. I've done it, but not regularly.

Not sure how your fuel tank/fuel pump is set up on your TH, and if its possible for lots of the fuel to siphon out of your tank from a leaking needle and seat in the carb. Depends on the height of the pickup and fuel level in the tank, fuel pump, the carb height, and angle of these components in relation to each other.
Most Onan carbs have a fuel solenoid in the bottom of the carb that should prevent this. But these solenoids are one of the main problems with the Onan carb. These solenoids get gummed up and stick closed or open.

I have seen a leaky needle and seat drain a complete fuel tank on other engines/vehicles. And suppose it is entirely possible on the Onan with the right set of circumstances.

Oh ya, If you don't do anything else, do the up date safety bulletin to your genset. It consists of removing the secondary fuel filter from the carb fuel inlet. And replacing it with a new Onan barb fitting.
Supposedly, this secondary filter has caused fuel leakage and fires. It is redundant and not needed. Onan does away with it since 2010-2011.

I added another clear plastic fuel filter in the fuel line before the pump under the toy hauler because I cut my fuel line for trouble shooting purposes, so used a fuel filter as a splice coupling.
Would not recommend adding any other filter inside the gen-set compartment. A good short properly routed fuel line direct from the pump with no splices is best in the genny compartment.

The old Onan Carbs secondary filters length and weight, combined with engine vibration with fuel hose weight on the end of it, caused filter to loosen up and leak at the fuel inlet fitting on the carb.
The new retrofit fitting from Onan comes with leaklock/locktite on the fitting threads. Screw it in very tight, it is a npt fitting. But don't break it or your carb.

We want to avoid all fuel leaks, a TH fire is to be avoided at all cost imo...

jmo

gummed up needle will cause it to overfill and leak. Had a friend that found his pan full of fuel. I gave him my old carb that I had cleaned with Seafoam and it runs fine now. Seafoam will save you lots of money if used regularly. Best cleaner there is. I have been using it for years.

Glad to hear you're making some kind of progress. Check the metal fuel filter (there are two, one at the carb and one at the fuel pump) and they tend to leak where they're crimped together during manufacturing. It might explain your gas leak. As for the 36 fault code, that was just an example, not a guess or anything else. Per Onan though, a 36 is;

Engine stopped without command by controller)
Corrective Action:
1. Gasoline Models – Check and fill the fuel tank, as necessary. (Note: The genset fuel pickup tube is probably higher up in the fuel tank than the vehicle engine pickup.)
2. Low Pressure LPG Models – Check and fill the LPG container, as necessary. On cold days the LPG container may have to be kept at least half full to provide the rate of vaporization necessary to keep
up with the genset fuel demand.
3. High Pressure LPG Models – Check and fill the LPG container, as necessary, and drain the genset LPG system of oil that may have migrated from the supply system (Item 5, Page 13). Make sure to
re-close the drain valve.
4. Secure the spark plug leads on the spark plugs (Page 20).
5. Replace the spark plugs (Page 20).
6. Service the air cleaner (Page 19).
7. Check for mechanical damage.

Here's a link to the manual in case you don't have it "click here" and be sure to check your fuel line running from the tank to the generator. If you disconnect it at the filter on the underside of the unit before it goes into the fuel pump, you can blow into it and listen for air escaping somewhere otherwise it should blow bubbles back into the tank.

OK, this is weird. I went out this morning. Pushed the PRIME button and tried to start it. It did not start. I went out and took the cover off and there was gas everywhere. It wasn't quite dripping out the bottom but there was a layer of gas on everything. I could wipe it up with my hand. As I said earlier, it really smelled like gas, now I know why. I went back into the trailer and the gas gauge showed EMPTY!

The last time I looked it was at 3/4 full.

I am concerned the gas gauge is not working properly. In hindsight it does seem weird to me that I could run the generator for nearly 7 hours AND fill the quad once (5 gallons) and still have 3/4 of a tank. I did move the trailer this weekend and maybe that caused the sensor in the tank to become "unstuck". There is no way it could go from 3/4 to empty just sitting there unless 1)there is a leak 2) someone is stealing my gas - the trailer is behind a locked fence 3) the gas gauge is not working, or a combination of the above.

My guess is that it won’t run because it is actually out of fuel but I don’t want to put more in if there is a leak. I probably should take it in as it’s still under warranty.

after u try the can and still no run spray some carb cleaner through air filter if it starts then u need a new carb,.

Mr. Sandman,

Thank you! I actually went back out last night and did just that. You nailed it. It was code 36. That's a bit strange to me because the fuel tank is 3/4 full. The trailer wasn't TOTALLY level so I leveled it and will try to start it again today.

Strange thing is that it ran fine the first two months I went out and exercised it but the third it wouldn't stay running.....

Dan

I use stabil to keep the fuel and also use seafoam. The best cleaner ever. It will make a difference. I use seafoam in every gas or diesel powered item I own. Started using it yrs ago in my classic cars. Stabil is not a very good cleaner. Those onan carbs are $280 @ Cummins.

You need to read the second serious of flashes of the code. The first code was three but there is a second serious of flashes for the second part of the code. For example, 3 + 6 = 36. If you don't have a manual let me know what the series of flashes is and I'll look it up in mine. Or, you can always download the manual for your generator on the Onan website.

I haven't been home during the daylight to look at it yet, however I went out tonight and tried to start it. I accidently pushed the button to "START" rather than PRIME and it started! It ran for about 10-15 seconds and died. The code (light) flashed was 3. That indicates Service Required.

Any further thoughts?

Hey Dan,

Try pulling the fuel line off of the carburetor and stick into a glass jar, then run the fuel pump to verify pump is working and fuel filter in not plugged. The glass jar will let you easily see impurities in the fuel such as water or air. Air would indicate a leak between the pump and the fuel in the tank. On a new unit such as yours, manufacturing debris in the tank and/or lines would be a likely cause of a clogged fuel filter this soon. If the generator has recognized a problem it will store a code, the codes are read from the light on the "Onan" start switch in the coach or on the generator itself. The light will flash two numeric sequences, for example: three flashes, pause, six flashes would be a code "36", a Google search will give you an explanation of the code(s). These gensets are good units but do not tolerate bad fuel, I have over 300 hours on my 6 yr old unit with no problems. Hope this helps, Mike