Onan 6.5 not getting fuel

87Itasca · February 06, 2017, 12:12 PM

Hi all,

My Onan runs well when it gets fuel, however it has been increasingly more of a problem, and now it will not run.

Pull the fuel line off at the pump, two little drops spill out. Suck on the line, and I can feel myself sucking air and the occasional bits of fuel, which come out the other end as a short sporadic dribble.

I have replaced the line from the genset case to the fuel pump. From the back of the case to where I lose sight of it above the tank is metal. So either the connector on top of the tank is rubber and cracked, or my problem lies in the tank.

Can I just cut a hole 1/3rd of the way up the tank, make a grommet, and push a rubber line through there? :)rotflmao

I have no idea how to drop that massive 80 gallon fuel tank that is currently 7/8's of the way full of gasoline, but I'm not too keen to try. I can't even get under the front of the motorhome as well.

I think Rick had a trick for this I read sometime last year, but I cannot remember what thread it was on now.

DRMousseau · February 07, 2017, 01:29 AM

OMG!!!!
DON'T be getting carried away yet!!!!

From your description, I'm thinkin' your issues might on top too, or maybe even be in your tank!!! Like uhhhhh,... how much fuel do you REALLY have in your tank??? D:oH!

Are you CERTAIN you have 7/8ths tankful??? and that your gas gauge is REALLY workin correctly??? The genny pickup is shallower than the engine pickup, of course. That's so we never run the tank dry on the genny and can't drive to gas station for more. If your tank is 7/8ths DRY, then you don't enough for the genny and its been getting worse till it finally got to this point. Try adding 5-10gals to tank and try again,.... been there, did this!

HATE sticky gas gauges!!!

IF, you really DO have 7/8ths tankful,.... try blowing into that last line before disappearing over top of tank. Thinkin you already have maybe. You should hear bubbles in the tank, IF the drop inside is intact and actually in the fuel. If you can get this line below tank level outside the tank, you should also be able to siphon from it too, although you noted you get nothing but air and a couple dribbles. IF you can siphon from it, but it stops quickly,... you may have an unseen crack, loose fitting, broken connector, or some other source of air leakage that may be plaguing you and has gotten worse, jus as you suspect.

I might also try taking the last possible end to the tank, and place it in a gas can or tank and try starting genny again, to be SURE issue isn't something other than inside the tank. Genny starts and runs,... than you know it that last line or your outa gas. Done this too. W%

Dropping a big tank like ours isn't anything I'd wanna do either. But ya REALLY don't wanna hole in the SIDE of that tank!!! A drop in the side of the tank is jus a huge problem of leaks and safety, plus no real good limit of fuel use,... you could still run tank dry on genny. This was done by the PO of my previous ol' Winnebago and "I" was the one who had to live with it!!! I'd rather a tee in my engine line as a fix!!! Could still run tank dry on genny, and might cause some starting issues of main engine. Would need a check valve in that line so engine doesn't suck from genny. But I wouldn't have to drop tank OR put another hole in it!!! Do these things have the main fuel pump IN the tank??? or is it some typical fuel pump outside the tank (electric or mechanical) leaving nothing more in the tank but drop lines and vents???

DAMN! I hate dropping tanks and messin' with gasoline!!!! YUCK!!!! And YOUR RIGHT!!!! Ya can't even hardly get under there!!!!

TerryH · February 07, 2017, 02:06 AM

I agree with what Dave posted. Dropping the tank is your last check. What I would do - assuming you do actually have more than 1/3 tank of gas on board is:
Get a piece of clear hose - TEMPORARY ONLY - and run it from your gen. pump to a gas can. Try starting the gen while watching the hose to see if the pump is actually drawing fuel. If no, suspect gen pump. If yes, but no start, suspect pump to gen carb or carb problem, or lack of spark or air. If yes and it does start, suspect line from gen pump to gas tank.
It is a gas engine and as such requires fuel, air and spark to run.

87Itasca · February 07, 2017, 08:29 AM

Something is funky here.

Took it for a drive last night, and figured, just for kicks, to hold down the start switch inside the RV. Gen cranked for a couple seconds and fired right up. Turned on both the roof A/C units, and the whole thing ran the whole hour I was on the road.

Cranked it over this morning about 6-7 seconds from inside the coach, and it starts up. I think it isn't getting enough fuel though, as when cold, it will generally surge for a little bit before it evens out. Sometimes it stalls completely, and will not start. I check the fuel supply and sure enough, no gas.

Gas gauge is correct. I brimmed the tank last fall when the hurricane was coming in case we needed to evacuate, and never did. Took a trip with it a couple weeks after, about 120 miles round trip, and I was just over 3/4. After my drive yesterday (with the genset running) I'm sitting at about 5/8's.

When I blow in the tank, I mostly just hear me blowing air through the line, and bubbles here and there. It's not a consistent sound, therefore my reason for suspecting something in the tank, or on top.

legomybago · February 07, 2017, 11:27 AM

I tried to put a quote here...didn't work??

Dropping your tank is the only way to for sure understand your fuel system.
BUT first try this......

I would unhook the fuel line from the genny at the carb, point it in a safe direction or a bottle, then fire up your motorhome and see if fuel comes out your genny supply line. Sounds to me like your genny is getting it's fuel supply from your 454 fuel return line. You said the genny ran great for an hour as you drove around.

Rickf1985 · February 07, 2017, 11:47 AM

One of the things I am getting from this is that the gas in this thing is over a year old, Just something to think about. Could have had phase separation and damaged pumps, filters, carb, any number of things. Also could have collapsed a fuel line.

87Itasca · February 07, 2017, 12:30 PM

Gas is about 4 months old, treated with ethanol STA-BIL prior to the hurricane. Still tastes like fresh gas

Gas line isn't in the return line. It ran fine for an hour today started up by the switch inside before I shut it off. Started up fine by the switch just now too. Aggravating thing.

legomybago · February 07, 2017, 01:21 PM

I had similar issues with our Onan running great one day, then like crap the next? After taking a look at the newish fuel line I had already replaced (all the way to the tank), I noticed one of my hose clamps loose at the fuel pickup on top of the tank, sucking air. I figured this was the only problem due to not getting good fuel flow through the hose....Tightened it up and the Onan ran great for a bit...Next camping trip we were back to the genny running goofy, surging some, and then sometimes wouldn't even start. pulled the carb, found a chunk of crap blocking fuel on the needle assembly. It has ran like a dream ever since, this was a year and half ago...

Rickf1985 · February 07, 2017, 01:42 PM

Mine was acting up right before I moved it before my surgery, all the symptoms of no AC power so it would not stay running after the start switch was let off. Resigned myself to the fact I would have to clean the commutator and then the day before the hospital I was moving the RV to a different spot and tried starting the generator and it fired right up and ran perfect? Go figure. I let it run under load for an hour plus and no problems. I has sat for a couple weeks now and will be at least a couple more before I can get out and try again but we will see. You just got to love the old stuff, just keeps you on your toes.

M & J · February 07, 2017, 05:59 PM

Like you Rick.. :)rotflmao

legomybago · February 07, 2017, 06:19 PM

DRMousseau · February 07, 2017, 07:47 PM

This reminded me that I had passed up some of my monthly checks around here, of which the genny and engine were a part of. AND genny fired up instantly, no problem, ran smooth as ever. The big 460 though, took the battery right down in it's reluctance. A quick jump, a bit more cranking, and jus as I was givin' up,... it came to life. Within minutes it was jus fine. Thinkin' I woke it from a deep hibernation.

Suppose to be 10deg tonight thru tomorrow night,... battery is chargin'.

Issues like yours though,.. is what keeps us up at night.

CapnDirk · February 09, 2017, 01:53 PM

I'm seeing a common theme that peoples generators fired up after the RV was moved. Is anyone parked on a slope? I just replaced all my fuel lines and the supply to the genset is coming off the return line.