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McFalls2014's avatar
McFalls2014
Explorer
Oct 06, 2020

Lots of Problems

We bought our first toyhauler 2 weeks ago. It had sat a while before we bought it and it has been a process getting everything in running order. It has an Onan 4000 generator on it along with the fuel tank and pumping station. Here’s where we’re at.....
There’s a tube hanging from the top of the fuel tank. Vent hose? Nevertheless it’s dripping fuel. Not pouring but its enough to make a noticeably big dead spot in my grass. The tank is building pressure so much that when I unscrew the fuel cap it actually pushed fuel back out. Pump station isn’t working at all. The motor runs but no fuel comes out. The generator will run for approx 30-45 minutes then shut down like it’s starving for fuel. I feel like all of this is linked to one issue but don’t know what it is. Help Please!!
  • McFalls2014 wrote:
    dedmiston wrote:
    Try cracking your gas cap and run it again. If it's not venting properly, maybe it's starving the gen for fuel.

    Is it hot where you are? Maybe the tank is so full that its burping fuel out of that lower vent line as the fuel expands.


    Its not hot, in the low 70s. Tried cracking the cap yesterday and it ran a little longer than normal but still shut down. What has me really confused is what is the line running from the top of the tank dripping fuel? If thats the vent line it should be venting with or without a vented cap I would think. Correct me if Im wrong as we are new to all of this. If it was clogged how would it drip fuel?


    It's possible that it isn't clogged, but just poorly designed. Maybe it's too small to vent enough, but large enough to puke out some gas. Those actions also work in the opposite direction of each other, so maybe a spider web is allowing gas to drip out, but won't let air in?

    What brand is your hauler and how long did it sit? And how many hours are on the gen? This will tell you how much the previous owner used it and whether he used it enough to service it or not.

    Also, I just re-read your original post and now I'm not sure if I'm picturing your setup correctly or not. Do you have separate tanks for your gen and fuel station? Or do they share a tank?

    Brand: We love our hauler, but the manufacturer didn't have much experience with toy haulers and a lot of the systems were designed poorly. Luckily our gen has never been a problem, but the fuel station doesn't vent well and it will suck itself inside out if I don't crack the gas cap before I pump fuel into our buggy. I only bring this up because there's a difference between "broke" and "designed by morons". You need to figure out which category you're in before you can fix it.

    Sitting Around: If your hauler has been sitting around for a long time with gas in the tank(s), then that could explain the rough running. You don't know yet whether the gen is getting starved for fuel or if there's something else wrong with the gen. Maintaining the gen is pretty easy, so I would start by performing all the basics: change the oil & filter, plugs, air filter, and inspect the fuel filter (if it has one). Those fuel filters are known to be trouble and they're cheap enough to just replace it even if it isn't part of the problem.

    Next I would deal with the fuel. It's not like a bike where you can just drain the tank into a 2 liter Coke bottle, but you can siphon the old gas into a couple of jugs while you troubleshoot this. I would siphon out as much of the old gas as possible, pour in a bottle of Seafoam and new gas, run it long enough to let the Seafoam get into the carb, and then let it sit for a day or more to let the Seafoam do its thing and then test it again. With fresh fuel, new oil & filter, new plugs, new fuel filter, and new air filter, it will hopefully be happy again and run like normal.

    If it sat for too long without being exercised by the previous owner, then there's a good chance the carb is varnished. People will tell you that they service their own carbs, and Onan will tell you they can't be serviced. Who knows. They aren't very expensive to replace though.

    About the pumping station...

    There's a notorious problem with the gears in the pump handle. I can't say if this is your problem or not, but post in the Toy Hauler Forum here and we can work with you on that. Basically, there's a plastic gear in the pump that swells up. I think it's about the diameter of a quarter and the thickness of two or three quarters. When it dries out (like after sitting unused for a long period of time), it swells up in thickness. The fix for this is to either replace the gear or remove it and sand it down 1MM at a time until it works.

    The gear problem is a weird one and it's been an issue for more than 15 years that I can remember. The weirdness is that some people have the issue and it's like herpes and never goes away. Those people have to keep a baggie of spare gears and replace them every year or so when they go bad. I didn't use the fuel station on my last hauler much and didn't mind when it stopped working. I use the pump all the time on our current hauler and it's never given me any trouble (except that I have to crack the gas cap every time I use it).

    Sorry that none of this is any kind of magic bullet answer, but I bet we'll get you fixed up.

    And either way, drop by the Toy Hauler forum and introduce yourself. Add your hauler info (and the toys, if you feel like it) into your profile so folks will know your setup better.

    Take care.
  • Sounds like a vent problem.
    - When it gets hot, the tank pressurizes and if full can push fuel out when you crack the gas cap.
    - When running the generator, at first the tank is pressurized but as the generator pulls fuel, the pressure comes down. But eventually, it gets goes negative and resists fuel being pulled out to the generator.

    As mentioned, try cracking the gas cap and test the generator. It's not a permanent solution but at least it gives you a clue what's happening.
  • A vent hose out of the top of the tank can not push fuel out unless the tank is filled to capacity and the fuel expands. If the generator is running there is no way the tank is over full.
    I'm thinking that hose is not a vent. And that the connection inside the tank goes to the bottom of the tank. That line may have something to do with your fuel station issues. For now I would plug it so gas stops leaking out.
  • dedmiston wrote:
    Try cracking your gas cap and run it again. If it's not venting properly, maybe it's starving the gen for fuel.

    Is it hot where you are? Maybe the tank is so full that its burping fuel out of that lower vent line as the fuel expands.


    Its not hot, in the low 70s. Tried cracking the cap yesterday and it ran a little longer than normal but still shut down. What has me really confused is what is the line running from the top of the tank dripping fuel? If thats the vent line it should be venting with or without a vented cap I would think. Correct me if Im wrong as we are new to all of this. If it was clogged how would it drip fuel?
  • Ron3rd wrote:
    I don't know much about your setup but any gas tank I've ever seen was not pressurized and spitting fuel.


    Yea thats why we are confused as to what is going on.
  • Vw triker wrote:
    Plugged vent on the fuel cap?


    We thought maybe its the fuel cap. On the top of it it says vacuum only so maybe we need a vented cap?
  • Try cracking your gas cap and run it again. If it's not venting properly, maybe it's starving the gen for fuel.

    Is it hot where you are? Maybe the tank is so full that its burping fuel out of that lower vent line as the fuel expands.
  • Ron3rd's avatar
    Ron3rd
    Explorer III
    I don't know much about your setup but any gas tank I've ever seen was not pressurized and spitting fuel.
  • You are at moving through the whole system checking everything. Fuel line partly clogged?

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