Check valve in fuel line somewhere?

[Bullfrog]

Here is the situation. 86 GW, just rebuilt the carb, new fuel pump, new fuel filter, new gas lines from carb to pump. No leaks I can find from the fuel pump to the tank. It runs great. Leave it sit for a day and you have to crank for a while to get the gas back up to the carb. Fuel gage swings when your on the road. Registers correct when still for a while. Question is...is there a check valve in the fuel float assembly or am I missing something else.

[440sixpack]

Your fuel pump should be the only thing between the carb and tank to block backflow.

I had the same exact problem, do you have an Edelbrock carb? I don't like them anyway so I put a Holley on it and problem solved.

I really don't know how the Edelbrock was doing it, it wasn't leaking and it was almost new. I really didn't expect the carb was the problem but it was.

You could have a bad fuel pump. just because parts are new doesn't mean they good anymore with all this Chinese junk.

[rapom]

Common problem with today’s gas. It is blended differently then when carbs. we’re common. It evaporates very easily in a carb which is why it is empty after a day or two. Evaporation doesn’t happen with fuel injection.

One solution is to use an electric pump to prime the carb. before you start the engine.

I did this to one of my cars for a quick startup after sitting. I have a electric fuel pump just outside the tank and a bypass fuel line teed around it with a check valve so the stock mech fuel pump can pull fuel around the electric pump. The electric is only used to prime the carb. Plus it helps with vapor lock issues which I haven’t had yet

And this is for an edelbrock/ carter type carb which seem to be most susceptible to this problem

[TexasJ10]

Mine has always done the same thing. Rebuilt carb with no change. One thing some have flagged as causing this is improper orientation of your fuel filter since it also serves to return excess fuel to the tank. If the return is not orientated at 12:00 the theory is the fuel can drain back from the carb. It never made any difference in my situation. I think it is much more likely to be the filter than a fuel pump. Maybe my filter is too far below the level of the carb and it still allows drain back. I don't know.

[babywag]

It's the gas.
No way for fuel to get past needle & seat.
If it isn't leaking out of power valve, etc.
Been an issue for years w/ carbs and today's "fuel".
Real gas doesn't do it. It's not just a Jeep thing.

[440sixpack]

I have 4 classic cars and this Jeep and the Jeep is the only one that does it. all running non ethanol super.

I did away with the return line and it still did it.

[TexasJ10]

Mine did it long before ethanol was added to fuel. That's not to say some other additive doesn't cause it though. If it's not moving past the needle I guess it must evaporate out for some reason with the carb design.

[rapom]

Even the 100% gas sold nowdays is different than the 100% gas of 30 years ago.

[TexasJ10]

Even the 100% gas sold nowdays is different than the 100% gas of 30 years ago.

I think you are right. Gas in a gas can that I bought six months ago won't even allow my mower to run. It seems to loose all of its chemical power to make something run. I use stabil but it doesn't seem to work on the gas that comes out of a pump now. When I was growing up we could pour gas we bought a year earlier into a mower and it ran fine.

[rang-a-stang]

...just rebuilt the carb, new fuel pump, new fuel filter, new gas lines from carb to pump. No leaks I can find from the fuel pump to the tank. It runs great. Leave it sit for a day and you have to crank for a while to get the gas back up to the carb. Fuel gage swings when your on the road. Registers correct when still for a while. Question is...is there a check valve in the fuel float assembly or am I missing something else.

OK, here's my thoughts:
a) the bowl in your carb holds probably close to a cup of gas. There is no way that much fuel (good or not) is going to evaporate in a day. If you were evaporating that much fuel that fast, your truck would smell like a rolling gas can. My truck sat on jackstands for 6 weeks without firing then I replaced the fuel filter, and it still fired up fairly quickly when I turned the key. Even if there is no gas in your lines, your truck should fire right up and idle for about 20 seconds with the fuel in the bowl, which should be long enough to get your fuel through the fuel lines to the needle valve. So either it is leaking somewhere you can't see or it's not firing for a different reason than you think.
b) I bet you are losing fuel into your engine as it sits. So when you crank your engine the next day its a little bit flooded. I don't think its really fuel getting through the lines to the carb, I think it's fuel getting into the carb and filling the bowl.

Here's what I would do: let your truck sit for 2 days (so you KNOW it will be hard to start), pull the top of your air filter, spray a quick squirt of starter fluid down the throat, and blip the throttle once from the linkage to verify your choke is closed all the way. try to start it. If it fires right up and dies, your bowl is empty and you have no gas going into the engine and you need to figure out how your bowl is empty in just 2 days. If it fires right up and idles smooth and high, let it idle for about 30 seconds and blip the throttle to ensure the choke opens all the way and it settles into a low idle. If it won't start/fire with the starter fluid, you may need a tune up. if it stumbles at first, then starts to idle high, you may be flooded because fuel is leaking into you engine from the bowl.

Has it run/started correctly since you rebuilt your carb? you may not have the carb/choke adjusted correctly since the rebuild...
The fuel gauge is completely unrelated to your starting issue. I would focus on getting it to start correctly, then move on to the gauge...

[rang-a-stang]

Did you put the spacer between the carb/intake? I wonder if you are baking some of the fuel out. Also, is your carbon canister hooked up? If not, did you plug the port on the top of the bowl?

[mwood65]

wow

I have the same exact problem on my 74' Cherokee.
258 1 barrel yf carb.

It sucks.

[440sixpack]

I put the heat insulator between the carb and intake thinking that may help. it didn't.

it;s hard to explain, an Edelbrock can't really leak out and it can't siphon back. I have no explanation and I've tried to come up with one, I just know it doesn't do it anymore.

[Mr. Wilson]

The mechanical fuel pump should keep your fuel from draining out of your carb. Even though it's new it may not be good.

[Bullfrog]

It did this before the carb rebuild. It has new plugs, wires, dist. cap and rotor, new gaskets and isolator under carb and it is torqued to specs. I'm starting to think like Rang a Stang in that the fuel is going from the bowl into the engine. Now, what would cause this, power valve?