Accessing Onan fuel line at a 2004 Destiny gas tank

[royalabran]

So good news bad news for me on getting my Onan 4000 up and running. I've owned my 2004 Destiny since 2014 I have not used the generator much since buying it and actually except for the day I got it and tested everything (bought through a dealer) it has always given me problems. I usually carry a Honda 2000 if I think I'll need a generator.
Yesterday I disconnected the fuel line at a connection just under the generator and I dipped the line into a mixture of 1 gal gas and 12oz of seafoam. The Good News: Pretty much as soon as I primed and started the generator it ran as smooth as I've ever heard it both at idle and with the roof top AC/heat pump.
Bad News: Today I reconnected back to the main line and I'm back with the same rough and stumbling running genset.
I can see and feel most of the line back to the gas tank and it "looks OK" but I suppose it could be pulling some air at the tank connection? and it seems I'll have to drop the tank if I want to check that out.
Oh also the Check engine light is on and the code indicates large evaporative leak, maybe that is related to the Onan? The engine runs so nice I have put off looking into it although I did buy and try a new gas cap cleared the check engine light and it came back on in a few days.
Any chance someone has fixed this problem short of dropping the gas tank? or if they did drop the tank just run new fuel line or was there anything else to do to correct the Onan problem or any other suggestions?
Thanks, Roy
I have retired this year and now have time to address and fix many small issues that I have accumulated.

[BobW9]

I had what sounds the same with my generator, only it took multiple tries and me finally forcing a shop to change out the hose to fix it. 3 different shops tried and failed to find/fix the issue over a period of 6 months. No one believed me when I said I thought the hose from the gas tank might be getting bad. Once it was changed, 3 years ago, no more problems.

I believe that after 16-17 years (I have a 2000 Concourse), the hose was just getting dried up and would flex various ways during travel, and depending on how it settled when I got somewhere, it would work fine or it would cough/sputter/cut-out. Sometimes I would have a faint gasoline smell when I stopped after driving a while, but all the shops thought that was just from driving or fumes from filling the gas tank on the road.

I did see the old hose afterwards and there was no obvious cracking that shouted 'leak'. But all my issues went away when it was replaced. I think they did need to lower the tank a bit, but I'm pretty sure they told me they did not drop it completely.

And I later found out when looking underneath the chassis for something else, that they had not removed the generator like I'd explicitly told them to... they cut the hose just before it entered the fiberglass box and used a clamp to attach the new hose to the old hose. So I still have a short piece of the old hose that should be replaced. If it had turned out that short piece was where the problem was, I might never have resolved the issue and just stopped using the generator. People can be such jerks.

Bob

P.S. This was Light Truck Service in Rockville, MD. I do NOT recommend using them if you happen to be passing through the area and need service.

[royalabran]

Thanks BobW9 thanks for taking the time to reply with your experience.
So many Onan stories...
I have been through multiple shops as well. There are 2 RV maintenance shops in Fairbanks, been to both and hopefully they help others but I wasn't to impressed except for the bill for hourly labor that was impressive. I got excited when I found a cummings truck engine place in town and they bragged they have the best tech who could get me going without a problem. This is several years ago, parked my rig there, one week, 2 weeks no answer, found that no one even looked at it, repeat that same scene x 2-3 more weeks gave up drove home. Decades ago had a 2.8 Onan in a class B Dodge Xplorer hooked up to power some stuff in my house occasionally during power outages. It ran out of oil and quit. Pulled it from my rig and took it to a shop in North Carolina , ended up deploying times one year, came back home generator still not fixed. I took all the parts they had ordered took the genset apart, replaced a bent rod, put back together myself and it ran, not quite good as new, but it ran.
Anyway now that I know this Onan can run well I think the good part here for me in Fairbanks is that I don't need to go through the local RV shops and there are many other good garages that should be able to replace the fuel line for me.

Maybe as another trouble shooting measure I could try and replace as much of the fuel line that I can see and get to , which would be most of it except for the last couple feet that I think connects on top of the tank.

[Jlfchinook]

I have not changed the hose on my generator from gas tank, but if I ever have to drop the whole tank I would also change out the fuel pump with a new one. Not looking forward to the day that mine will quit! I still have the one that came with it, and at a 140,000 miles it has to be worn. Have relocated generator fuel filter to inside frame rail due to bad location of original.

[royalabran]

Jlfchinook thanks,
I have read other posts on changing the fuel pump while the tank has been dropped. My rig has only 64k miles and runs smooth as silk. I don't want to mess with that so I'd be reluctant to change the pump and don't really want to mess with the tank either.
I've also seen some youtube vids on cutting an access hatch right over the fuel pump. If this was just a plain old 2004 chevy 3500 I might consider that.

So I might as well try replacing the majority of the line that I can get my hands on and see what happens

[BobW9]

Be careful replacing the fuel pump. A couple service shops I've been to for other things said that they won't touch them any more on the older E350/E450 because they seem to sometimes get so rusted on that the bolts/bracket break off when trying to remove it. This basically means you need a new gas tank (according to them), and they said they've found correctly sized replacement tanks hard to find and expensive. I don't know if both these shops just had bad experiences, but the fact they didn't want to touch it and said "if it ain't broke, don't try to fix it", tells me I'm waiting until my pump fails.

Of course, I was nervous changing my original spark plugs and coils (at 115,000 miles and 19 years) given some stories, but that went easy-peasy. And I gave myself an upgraded 200 (220?) Amp alternator at the same time (they charged just $50 labor given that everything was in pieces and it wasn't hardly any extra work)

[royalabran]

So I changed most of the fuel line today except for about the last 18"-24" on top of the gas tank.
No change, the generator, after a long prime, starts easy but still stumbles.

I went back to the setup that had it running smooth.
1 gallon of gas with 12 oz of seafoam I had a little left from the cleaning 2 days ago.

I disconnected my new fuel line back to the generator and dipped that short line into a 5 gallon container of gas....runs rough..

Dipped that fuel line into the seafoam:gas mixture.... after a minute the generator runs good

So for my generator to run good I need to continue to run it on a mix of gas and seafoam? Does that give an octane boost or something? Is this cleaning the carb and eventually it will run good on straight gas?

So I think I'm back to thinking this is a carburetor problem from long periods of nonuse.

I have a new cheapy carb from Amazon so I guess that's next. Oh well, I was hoping seafoam would be my miracle.

[dougm]

IMO, the non-commercial cummins/onan generators are completely unreliable. They should be fuel injected, that would eliminate a huge amount of problems people have with them. I got so sick and tired of the one that came in my rig that i finally just went out and bought a brand new replacement. When it craps out i think i will just find a Honda, yank the onan and find a way to adapt the honda into that compartment. It seems like everytime you go someplace and need to rely on that generator, they dont work. They are garbage imo.

[royalabran]

My further ramblings and flailing attempts to get the genset to cooperate...

I have replaced fuel line and filter except for the first 18" off the vehicle gas tank.
Many rounds of seafoam
played with the governor adjustment screws, maybe to the detriment of the generator?

Today I replaced the old carburetor with a new one from Amazon.
Starts up and seems to run fine while idling. Under the load of the microwave it hunts? or surges? and then the microwave will give up after about 10 seconds. The old carb ran rich per the exhaust smell and light sootiness but I see an improvement there.
Seems to do OK with the AC, although I'm in Alaska and its 55 out this morning.

I have at different points adjusted every screw that has to do with the carb so those could now be problems as well but with the new one being preset I just bolted it in and didn't readjust anything.
So that leaves the governor, choke seems open when warmed up, maybe fuel flow, I have changed the spark plug

So spark fuel and air OK …. I guess I can speculate that surging while under load may mean the governor is to sensitive and I can try adjusting that screw per the 108 page manual I've downloaded from this site

[royalabran]

My further ramblings and flailing attempts to get the genset to cooperate...

I have replaced fuel line and filter except for the first 18" off the vehicle gas tank.
Many rounds of seafoam
played with the governor adjustment screws, maybe to the detriment of the generator?

Today I replaced the old carburetor with a new one from Amazon.
Starts up and seems to run fine while idling. Under the load of the microwave it hunts? or surges? and then the microwave will give up after about 10 seconds. The old carb ran rich per the exhaust smell and light sootiness but I see an improvement there.
Seems to do OK with the AC, although I'm in Alaska and its 55 out this morning.

I have at different points adjusted every screw that has to do with the carb so those could now be problems as well but with the new one being preset I just bolted it in and didn't readjust anything.
So that leaves the governor, choke seems open when warmed up, maybe fuel flow, I have changed the spark plug

So spark fuel and air OK …. I guess I can speculate that surging while under load may mean the governor is to sensitive and I can try adjusting that screw per the 108 page manual I've downloaded from this site

Well finally something easy!!
The microwave is not happy when it is run empty.
I put a cup of cold water in and it ran fine and the generator runs smooth under load.
Also tested it with an electric space heater and the generator runs smooth.
Roof AC seems good to go as well.
Time for a beer and to savor this brief moment when the Onan is happy with me!!