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Riding lawn mower mystery
So my sister moved into the city and I inherited their riding lawn mower for free, previously I was using a push mower. It was in pretty bad shape when I got it, but I welded the deck back together myself, got rid of all the bullshit safety features that make mowing a pain in the ass like being able to mow in reverse, and it's been going good. I've noticed however when I park this mower in my garage when the fuel tank is more than half full my garage smells so strong of gasoline that I'd be concerned if someone walked out there with a cigarette they might blow up. On the other hand, if I park the mower in my garage with the fuel tank less than half way full all I smell is grass clippings and no gasoline fumes. Obviously I'm fine with just refueling when I go out to mow, but I can't figure out why this happens. I don't see any cracks in the tank, there is nothing leaking out of it, the gas cap is in good shape, it's not overfilled. Anyone have any ideas what might be causing this? I'm thinking the increase pressure of the larger volume of gasoline must be putting pressure on something somewhere in the fuel delivery system causing fume leakage, but I haven't tried to rip that part of it apart yet. I was just wondering if anyone has seen this before.

The mower is a Troy Bilt Bronco, looks exactly like this one, mid 2000's. 42" deck:

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The forum poster formerly known as Emoticon...
No idea.

In my garage I have three mowers (one with 5 gallon tank), a snowblower, multiple handheld pieces, two 5 gallon cans of gas, and two smaller cans of gas.

I've never noticed a gas smell.

The "pressure" theory seems likely, although I couldn't say why.

My No-Spill brand cans will expand and contract like a motherfucker with temp changes. In heat/sun they swell - cold temps cause them to literally collapse inwards - the emptier they are, teh more they collapse.
Check the air cleaner and see if it has an excessive gas smell or is wet after it has been parked overnight with a full tank.

You should be able to install a shut off valve in the line if need be.
The Second Amendment does not GIVE us the right. It tells the gov they can not infringe our right.
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Might be a pinhole leak. You'd have to take the tank out completely to do an inspection.
tolerance for failure meter... LOW
I'll take a look tomorrow. I should also mention I left for a week out of town and came back on Wednesday. I didn't have time to drain the tank down before I left and it was in stink up the garage mode, but even after sitting for a week when I got home the smell was as strong as ever. Mowed the grass, didn't refill, parked it with 1/4 tank and it's back to smelling like grass in the garage.
The forum poster formerly known as Emoticon...
I'm thinking there's a dry-rot crack or pin-hole in the the fuel line between the tank and carb. Every gallon of gas weighs about 6 lbs so more fuel = more pressure in the fuel line. When the tank is full there's enough pressure to force the gas through the hole/crack, when under a half tank the pressure isn't strong enough to push the gas through. Fuel line is cheap so even if I'm wrong you're not out more than a few bucks. If there is an in-line fuel filter check the fittings/clamps there too.
Ammunition, it's the new lead bullion. Buy it cheap and stack it deep.
Leaky fuel line? Fuel tank cap gasket? Top end? Does it smoke?
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