DING!! In the shower and a light goes on for my fuel problem

[Dan Stuckey]

So my fuel problem didn't go away as I hoped and had a sucky day mowing this afternoon. 49 with a 59'' Woods mows, and mows well....well most of the time. Seems it'll run well for 30 mins, 45 minutes, whatever. Then it begins cutting out, at times stalling even if I push in the clutch.

I'm at the end of my frustrating day, backing it under the shelter for the day. Im sure its the carb that's screwing up and really want to send it to someone that knows these better than I and go over it good. So it shuts off and I thing, pull off the new rubber fuel line I just installed a couple weeks ago. Loosen the clamp quick, pull off the line at the carb inlet and just a drop or so of gas comes out. So I blow into the hose until I hear the gas bubbling in the tank, release and gas flows nicely. So I gather dirt, debris, rust must be gathering at the inlet to the fuel shut off.

Well in the shower this evening thinking about this and WHAMO!!!! It hits me. Is the gas cap vent plugged and negative pressure in the tank messing me all up? I have a new style cap on it but it is probably 15 years old or so. It stands to reason as my tank is clean and rust free inside, I never see and crap in the glass bowl. It must be the cap vent. I work on a lot of mowers and snowblowers and see this problem from time to time. So have any of you ever had this problem or heard of anyone that has? I cant get back to the Cub for a week but so anxious to run til the problem pops back up, crack the cap a bit and see if this is my actual problem. What do you guys think?

[Lt.Mike]

I had that happen with my JD lawn tractor. Learned to keep the vent clean.
Don’t know for sure if a Cub would do that. There’s lots of spots that the fuel travels from the tank through the carb that loose crud can block flow and make a headache for you.
Gotta ask, did you get the free replacement vented cap from IH?

[staninlowerAL]

Yes, that could be the problem Dan. Also the fuel passage from the tank to the sediment bowl is not totally vertical but has a short horizontal section where debris can get lodged. As far as I know there is no way to "rod" this out to clean it,

[Dan Stuckey]

I had that happen with my JD lawn tractor. Learned to keep the vent clean.
Don’t know for sure if a Cub would do that. There’s lots of spots that the fuel travels from the tank through the carb that loose crud can block flow and make a headache for you.
Gotta ask, did you get the free replacement vented cap from IH?

Cap looks like the updated free one. But just ordered a new one, not sure if its cleanable to open the venting.

[Dan Stuckey]

Yes, that could be the problem Dan. Also the fuel passage from the tank to the sediment bowl is not totally vertical but has a short horizontal section where debris can get lodged. As far as I know there is no way to "rod" this out to clean it,

Most of my fuel line is rubber and I just replaced it two weeks ago thinking it was eroding on the inside and causing my problem. Like I mentioned though, tank is near pristine inside, nothing like any dirt in sediment bowl and screen

[Lt.Mike]

A little debris can clog the valve area of the sediment bowl. Do you have a zenith carb?
My zenith carbs have a screen attached to the elbow that screws into the carb. I’ve had that screen clog and cause issues.
I gave the tank on Paula’s Cub a cleaning but I didn’t remove and rinse it so debris kept turning up. It would conk out and I’d poke a coat hanger into the pickup tube and it’d clear... until the next time it clogged so I picked up a small screen tube from eBay and inserted it into the bowls pickup inside the tank. It’s not a proper fix but it’ll do till I have the time to pull the tank. It runs fine now.

https://rover.ebay.com/rover/0/0/0?mpre ... 2618189035

[brewzalot]

Loosen the clamp quick, pull off the line at the carb inlet and just a drop or so of gas comes out.

Next time this happens instead of blowing in it, just try loosening the gas cap and see if the flow improves. That will tell you if its a venting issue.

So I gather dirt, debris, rust must be gathering at the inlet to the fuel shut off.

Sounds like you have something floating around in your tank. Pull the hose at the carb and let it run back into a gas can. Let it run a long time and see if it eventually changes flow or stops.

[TallCoolOne58]

When I originally bought my Cub, it had the safety cap on it, however some PO had repainted it in the past, and the paint covered the vent holes. I unplugged the holes with a safety pin. I also ordered a new freebie cap from IH. When it came, I replaced the old one with it.

One thing I will say, here in NY, most available pump gasoline is E10 (10% Ethanol). I could be wrong, but I think these caps are New Old Stock, from a huge run in about 1980, so IH could supply them for free. The 'rubber' seal does not seem to hold up well to Ethanol blended fuels.

On my acreage, as I travel on the sometimes uneven trails, fuel sloshing in the tank will contact the seal, and it will seep fuel. To compensate, I only fill the fuel tank with 5 gals.

[Mac AR]

I was having similar trouble with my Cub. The original style cap had no seal, but luckily I had a rubber gasket the proper size so I put that one in. Started having trouble with it dying after it got hot. Found that tank to be vapor locked, so went back to the shop and drilled the holes in the cap out. There are two, one in the top and one in the bottom. Both must be opened. That fixed it, but then I found out about the free IH cap so ordered one for both it and the 300. I haven't noticed them leaking, either. But I did fix my filler necks about 2 or 3 years ago so that may have helped.

Mac

[Dan Stuckey]

Thanks guys for all the great tips and ideas on this. Anxious to get back to her early next week and hope she acts up so I can test the gas tank vacuum theory. All symptoms point to that.