Another Carb/fuel Question

So spent 1/2 the day searching our forum about carb flooding after shut down. It runs as it should, normally, but it can be hard to start if hot and shut down to go into a store and then it takes a few pumps to get it started again. Searching the interwebs this appears to be common among older vehicles with carbs and todays ethanol enriched gasoline and lower boiling points of pump gas. (no expert here, just regurgitating information) If the gas heats up to boil, after turning it off, it can push it into the carb, land on the butterfly and leak off the main shaft and onto the intake manifold, which it is exactly doing on my 73' 258 Carter 1BB. The carb has been fully rebuilt and adjusted within 5 months with all new internal materials, acc pump, needles, check balls, springs etc. The float is never full of any fuel and it is adjusted as per the 73' TSM. It worked flawlessly for months and now my garage smells like a fuel factory every time I drive it and shut her down.

A solution is to run a 1 into 2 fuel filter without an orifice and vent vapored gas back to the tank. This 1 into 2 filter is mentioned by timgr in an older thread which started this one. This is a link to the thread:

Slowwwwww To Start

I would like to give this easy and inexpensive fix a try but I do not have a return line on my 73'. So could one run a vent line from the filter to a "T" in the fuel tank vapor vent line that attaches to the liquid check valve allowing for any gas to enter back into the tank or is that just a bad idea? I'm not really sure I want to tap another vent line into the tank directly and it didn't come with fuel return line that I can find in the TSM. It has vapor return lines that go to the liquid check valve and then to the charcoal canister.

Either way I'm brining it to you guys and see what I can do. If it's just an old carb, and needs to go, then I would be open to replacement suggestions as I have not been successful locating a YF that looks like mine rebuilt or new. Thanks

 

Whoa whoa whoa. Back up the truck.

"Pumping" a carb makes the flooding worse, injecting fuel from the accelerator pump on each stroke. That will kill a hot start.

The proper technique is to keep the pedal on the floor, holding it wide open and motionless while you crank to clear the excess gas.

Also, you will see old timers jam a screwdriver down the carb throat to hold the choke flap wide open. Make sure your automatic choke is functioning and is properly dialed in - adjusted to be "full open" when hot. One full stroke of the gas pedal is the protocol to 'set' the choke before cranking. If it's a manual choke, push it full off when hot cranking - and again be sure it is adjusted to be fully open.

 

Thanks Pete. I guess I chose the wrong way to describe what I was doing in that situation. I haven't been holding it full open but I do give it a "toe" worth of pedal and then hold that. The choke is automatic, not manual or electric. It is adjusted and works properly. It is in the 80s down here already and getting to temp takes no time at all, it is definitely wide open within just a few minutes.

 

Okay. So... is it "boiling?" Have you looked down the carb throat and checked if that is indeed happening?

If so, maybe a simple sheet metal heat shield would help. Some YFs used extra thick carb gaskets as an insulator.

But the design of the YF is such that overflow from the bowl is discharged under the bowl, on to the head.

 

I pulled the fuel line off after it had been running to adjust the metering rod and it looked to be boiling in the fuel line between the carb and the fuel filter, which got me thinking it could be that. I will have to put a clear line between the metal fuel line that runs in front of the valve cover to the carb to verify that it is actually boiling. That, or the active bubbling in the fuel line would be a lot of air, which could be a whole other problem. But like I stated earlier, it runs fine, this is after I shut it off.

I have seen it drip out of the center jet (I do not know what that jet in the venturi section in the center is called) which is regulated by the metering rod. Those drips then land on the main butterfly and end up leaking off of that shaft and onto the intake manifold. I know its not supposed to leak from there which led me to try and adjust the metering rod again and that only caused a bad low power "flat spot" when trying to slowly accelerate.

Edit: Oh and the carb is on a pvc spacer where it bolts on, so there is not metal to metal direct contact between the carb and the intake manifold.

 

This is where it is leaking from after shut off.

 

Two questions. What is the float setting? Does your fuel line run close to the exhaust? Sorry. One more. Is the tip of the needle in the needle and seat rubber (Viton) or metal?

 

Use a brass tip needle only........

 

The float setting closed is 29/64 about 0.45" or roughly 11.5 mm. The only reason I know that is because I had no idea what 29/64th looks like from the TSM, and the open is 1 1/4 open.

The tip is Viton




The fuel line is not directly near the exhaust but could probably be rerouted over the valve cover?



Right now I'm using a fuel hose over the metal hose as an insulator going around the front of the valve cover.

 

Pete, I'm not so sure it is boiling. It was just one of the recommendations by carb guys that could cause a flooding after turning off issue so I thought I would pose the question and see what experiences you guys may have had in the past.

That being said, I did try and test the theory but I didn't have the time to really heat soak the engine.






What I did find was that after getting it up to temp bubbles started forming around the tip of the metal tubing on the left and forming a larger bubble which eventually went into the carb. (this was after it was shut off, otherwise I didn't see any bubbles while it was running.) Was it something crazy boiling, absolutely not, and my carb seems to run just fine. Could the fuel be boiling in the float bowl after shutdown sitting on top of a hot exhaust, maybe? I may just be looking for something that isn't there but its worth a shot to see if there was anything going on with the fuel system there. Unfortunately I came up with nothing but theories. Had a good time testing it though.

 

What's going on here? The OP makes it seem like the boiling fuel is pressurizing the float bowl and forcing gas out through the booster venturi.

I would think this is unlikely, since the float bowl is typically vented to the air horn above the venturi. There is no way for vapor pressure to build up. Don't know much about the YF, but that's the typical configuration for carburetors. There's not a lot of volume between the fuel pump and the float bowl, and the plumbing should be sitting exposed in the engine compartment. Without the engine running, I can't see how the external plumbing can force enough gas into the float bowl to make it come out the booster venturi. Maybe there is a missing check ball or check ball weight in the carb body? And it's actually dribbling in all the time, but it's not noticed when the engine is running?

 

So, in that top picture, where is the spring I believe the needle should be riding on?

And BTW, as Timgr mentions, it is VERY common for YF rebuilders to lose a check ball from the accelerator pump circuit.

 

It's just in the needle in the picture. I was taking the picture to show the the Viton tip for scoutpilot.

It is very possible that something was misplaced or put in backwards. I just may need to do another teardown and check my work and recheck my adjustments.

 

Thanks timgr. It seems by the replies and testing that it does seem unlikely that it is boiling fuel and more of a carb builder error.

 

There is so much going on here.
Let's start with the fuel line. The single clamp over the hose to straight-tube connection is likely allowing air infiltration, hence the bubbles. Any tube over a straight pipe connection requires two clamps, aligned next to each other with screws on either side of the tube to avoid the "bunching" of the tube. And yes, it is too close to the exhaust manifold.
Due to the Viton (I hate Viton) needle, the float should be set to 9/32" as measured with the top inverted and the distance between the float tip, as it rests unloaded on the needle and the inside of the top without the gasket in place. It should look to be nearly horizontal to the top.
Your photo of the inside of the carb gives me a problem because you left the gasket in place and I can't see if the check weight is in its place in the acceleration circuit.

 

Things I did not know.

That will require some time. I will get the photo (without the gasket), the clamp and adjust the float. That is how I adjusted the float, as you mentioned, but apparently to the wrong height. May take a little while as I have a busy weekend but I will post what I find. Is it easier to just source a full metal needle and lose the Viton?

 

X2.....but please start with using a brass needle....... I can see the famous " Viton" TIP wear RING from here & I just had Cataract Surgery !

 

This is a bigger problem than most people realize. See if you can find a station in your area that sells "pure" gas (no ethanol). I always use that in my carb'ed vehicles and they run better.

 

You show a late, late model YF. I don't think you can find a brass needle retail for that model.

 

Yeah I noticed that too, an obvious wear point. It's only a matter of time before I will be replacing it. Might just get a few spares unless I can find a carb with the old style needle and seat, apparently they don't make them anymore.

I couldn't find one. Mike's Carburetors states that they are no longer available and he is the one I bought my rebuild kit from.

Well I went and adjusted the float level for Viton and as for now it seems to be working. Maybe the incorrect setting may be the link to the flooding after I shut it off. In any case I am going to reroute the fuel line over the valve cover and away from the exhaust manifold just to be sure its not heating the fuel in the metal fuel filter.

I drove it down to the Keys this past Saturday for a Jeep meet and it performed excellently. It didn't leak when we got down there and I check right away.

I do appreciate everyone chiming in and helping me through that exercise.

I think I can get that not far from my house. Is that "Rec" gas?