I have a gravity-fed-gas and propane dual-fuel pull-start 4-stroke portable generator which works well and with no problems. I am thinking of adding an add-on remote start so I don't have to go out to it to start it.

I will of course have to go out to the generator in a long power outage to re-fuel it, but for convenience' sake, a quick push on the remote start at night when the bears are out and about can make things nicer, and re-fueling in the morning would be safer.

All of the engine's parts are in proper working order, with no damage.

If I leave the generator fully fueled with stabilized gas and the fuel petcock turned on, or if I leave the propane tank connected and the tank valve turned on, so fuel can flow if the engine is remote-started, I am concerned that there might be normally-occurring situations where the gas or propane could leak out while the engine is off.

I did a web-search for why small engines leak gas, and came across a list of reasons a leak could occur:

  • carburetor problems: bowl gasket cracked; float or needle not sitting correctly; body has cracked
  • fuel hose or tank has cracks
  • primer bulb is brittle (this generator has no primer bulb)

I did not locate a web source for why a propane-fueled engine might leak.

Assuming none of these engine troubles happen, can the engine turn off and come to rest in a normally-occurring situation where the gas or propane could leak out?

(If it is necessary to separate the gas and propane fuels to different questions, that would be fine.)

1 Answer 1


I don't know of anything that would cause the propane to leak, but if you want to know for sure, you can turn off the propane valve at the tank, wait 24 hours, and then crack open the propane fitting at the generator. If you get a hiss of propane escaping, it did not leak, or it leaked so little that it won't matter.

It's a pity that dual-fuel generators don't start well on propane -- at least not the ones that I've dealt with -- but tend to start easily on gasoline, then you can switch to propane when warmed up. If your generator starts well on propane, it may be the best choice to skip the gasoline altogether, because if you leave the gasoline supply turned on for weeks to months at a time, there will be problems.

When you stop the engine, the carb's fuel bowl is full and the surface of the gasoline in the bowl is exposed to the outside atmosphere via the air intake to air filter to air intake runner to the carb's main jet that's in the airstream at one end and submerged in gasoline at the other. Gasoline will slowly evaporate through the main jet and escape to the atmosphere. Over time, as the gasoline evaporates, the level in the bowl will drop, the float will drop and the needle valve will admit fresh gasoline to refill the bowl.

Eventually, after months, what you'll have in the bowl is like the residue in a still pot: a thick, syrupy liquid, which represents the fraction of gasoline that doesn't evaporate readily except at elevated temperatures. If you try to start the engine at this point, you'll be out of luck because this syrupy liquid won't atomize and evaporate enough to make a flammable mixture in the cylinder. You'll get out a can of ether and eventually get the engine started, but it will run rough and dirty until all that oily residue is washed out by fresh gas.

If you make it a habit to start and run the generator for a few minutes, say once a week without fail, you won't get enough evaporation to get that oily residue. If you start the generator on Sunday mornings when all the bears are at bear church, it will be perfectly safe.

You might also consider adding a 12V electric valve to the fuel line that your remote starter control could energize. You could wire it with a DPDT relay that, once the coil is energized, it self-latches ON until you interrupt the coil current with a pushbutton SPST NC switch to turn off relay coil and therefore the fuel valve until the starter is next energized.

If left idle for months like that, the single bowl of gasoline will evaporate, but that's not enough gasoline to create a carb bowl of gasoline syrup. Even better would be to cut off the fuel and run the bowl dry when it's time to shut down.

  • Thanks MTA, this is really good insight! I had not thought about the recurring evaporation and refill in the carb bowl, very interesting failure mode. Good trick on testing the propane leakage too. Wiring that valve is doable, will look around for such a thing. Sep 29 at 22:07
  • BTW, I loved "bear church"! Sep 29 at 22:07
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    @Triplefault The fuel evaporation from the bowl is the reason you'll find a fuel petcock on nearly all small 4-stroke carbureted engines. I've never seen one on a 2-stroke (no carb bowl) and diesels are all fuel injected so they don't need them either. See ya 'round the block at SE-DIY.
    – MTA
    Sep 30 at 0:45

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