So, many of you helped me out a month or two ago diagnosing problems with my outboard
(6HP Tohatsu, using the internal tank. Just about a year old). I got the carb cleaned out (4 or 5 times by the end), got my fuel
lines cleaned out, and everything was running great. Until it wasn't anymore. But now I'm much more familiar with the little bastard, so I think, "Yeah, I can handle this. I know what I'm doing now." HA! Pure hubris that thought was!
So now for the saga of what I've done to it this time. Beware, it's a long 'un. Specific questions are at the very bottom for those who only want to skim.
It was running fine, but then abruptly started having a problem where whenever I tried to throttle up, it would die. Occasionally, I would get it to rev up and drive, but then the power would be all over the place, surging and waning every few seconds. Most of the time, it would simply stall and die when I tried to open up the throttle.
A bit of Googling, and an old thread from this very forum has me convinced that the carb must once again have a little something in it. Supposedly, a little debris in the high-speed jet could cause it to fail to transition from the low-speed jet.
So I break down the carb again and have a good close look. And what do you know? There's a little bit of some kind of fiber in the high-speed jet. Like a short hair or something. So I clean that out, give the whole carb a thorough once over while it's out, and put things back together with all the confidence of a toddler in a Batman shirt. "I've solved
it!" I mutter to myself, absolutely filled with pride at conquering a simple bit of maintenance
Except. It won't start now. So I start looking over my work
. I must have missed something on the reassembly. But it all sure looks right. I reference some photos I took before taking it apart. Yep, all looks good here.
So it's back to basics now. Why won't it start? Do I have a spark? I spray some starting fluid in with the spark plug
. It lights that off no problem, but the engine
doesn't run. Do I have air? Well yeah. It's just a simple little rubber hose to let air in. I take the hose off and make sure there's nothing blocking it. All good. So it must be fuel
. Sure enough, I'm not getting any fuel to the carb anymore!
Well what the $&%! What changed from when it was running, just not right, to now? I had of course shut off the fuel valve before taking the carb out, but it was open again. I start taking off hoses.
Not only am I not getting fuel to the carb. I'm not getting it to the fuel pump
either! That's odd. Gravity should have pushed fuel to the bottom of the pump
. I keep working my way upstream, trying to find the gas. It turns out, even the very first hose connection after the internal fuel tank
is devoid of any actual gas. Hmmmmmmm.
Suddenly, inspiration! The vent cap on my fuel tank
isn't properly allowing air to flow. So the fuel is vacuum-sealed in the tank and can't run down the hose! I take the fuel cap all the way off, and fuel starts streaming out the hose!
I'm once again on top of the world! It was a tricky one to spot, but I found the problem. This was probably the real reason I couldn't throttle up as well! When I asked for that much gas, it couldn't pull enough out of the tank because of the vacuum seal, so it stalled! I start putting all the hoses back on to really test my theory. I quietly chuckle to myself, thinking "it's a good thing cool heads prevailed. All I had to do was go slow and methodical, and not get frustrated. I'm such a genius and all-around capable guy!"
I go one by one on the fuel hoses. Each time I reconnect a hose, I open the fuel valve and ensure a little gas dribbles out the far end. I get back to the fuel pump
. I hook that back up and give the cord a pull. A little gas comes out of the top of the pump
, I'm in business! I hook the hose back onto the carb, the final connection!
I give her a good 5-10 pulls. It makes sense it wouldn't start immediately. The carb is dry and I have to work
a little fuel into it first. But after 10 pulls, I'm still getting nothing. No cough, no nothing. Hmmmmm.
I unscrew the little drain in the bottom of the carb bowl. Nothing comes out. Curioser and Curioser! I know I'm pushing gas into the carb. But it's not making its way into the bowl.
I know! That damn float valve must not be working right. The carb isn't letting any fuel in! So the carb comes off once again. I have a real close look at that float valve, but it seems totally fine! But I'm struck by a clever idea. I put the carb back on the engine
, but with the bottom half of it still taken apart. The float valve now hangs down in the open air, with no bowl underneath it to float it up. I put a little cup under to catch the gas, and open the fuel valve.
Boom! fuel dribbles out the float valve just like it's supposed to! I use my finger to "float" the valve closed, and the fuel stops just like it's supposed to! Now I'm really and truly confused. If the float valve is operating correctly, and I can get fuel to run out into the open air where the bowl normally is, why was the bowl empty when I unscrewed the plug
?????? Maybe it was just a little stuck, and I have it freed up now?
I reassemble the whole thing and give it one more try. Still nothing. Still no fuel in the bowl on the carb! And that moment was the titular end of my wit. My wit could go no further. I had reached the extent of the reach that could be provided by my wit. And so I put a couple of questions to the infinite wisdom of the forum:
1. What the heck is happening here? Is the float not able to move freely in the bowl? It looks like it should, but I can't actually see in there when the bowl is on to know if the float is moving.
2. Is my hypothesis about the vent cap reasonable? Could that have been the main problem all along?
3. What does one do about a vent cap that doesn't let air in? I can run with the cap off, but not if there's spray or rain. Replace the cap altogether?
4. Back to the carb: is it even worth continuing to mess with it, or should I just buy a replacement carb? Anybody have a good source for one?