What causes carb float bowl to drain

[chichiflys]

If my truck sits overnight and it's cold out there is no more fuel in the sight glass...takes a while to get it started, but it runs fine afterwards...so I think the fuel bowl is draining dry....

Total carb rebuild?

 

[TheGr8Doughboy]

I think a failing fuel pump will do this

 

[AKcruiserfreak]

I have this exact problem as well as slight stumbling when cold. Hope you figure out what the problem is.

 

[PAFJ]

This is normal... overnight or extended periods I think the fuel evaporates out. Mine is the same way, a few pumps of the accelaerator in the morning and its good to go. I have a new fuel pump and it still does it so I don't think it's a fuel pump problem. Just make sure fuel is not leaking out of the carb where you don't want it to.

 

[Pin_Head]

It takes a long time to start because the fuel pump needs to refill the bowl.
Mine leaks into the intake manifold as I can see a big puddle of fuel there after sitting overnight. It is not boiling out because it still leaks even when I fill the carb without starting the engine. I thought it might be siphoning out the idle port or transition slots because the air vents were plugged, but I have rebuilt it twice and verified that nothing was plugged. I am thinking now that the bowl may be cracked or have a leak in one of the plugs that seals a drilled fuel passage. My next step is to add a fluorescent dye to the gas in the bowl to see if I can find where it is leaking.

 

[lathrop]

The problem is uasualy that the float valve doesn't seat properly. could be dirt. However once you disaasemble the carb you may as well replace it.

 

[lathrop]

its the needle and seat that need replaceing. not the float. nomeclature mistake?

 

[TheJackRabbit]

Gravity.

 

[IZZYDUSIT]

Culd be casting plug inside the carb. normally JB WELD takes care of it if it's the problem-ck the accelarater pump action-it should have a good squirt into the venturi (throat).

 

[Mark W]

An OEM carb can not drain back down the fuel line. The inlet is above the fule level in the carb

Unless you have a cracked casting there is no way for the bowl to drain downward either. There are no downward passages, all the fuel has to go up before it can go down.

Except in very hot temps, the fule will not evaporate out of the carb "overnight".


Having to work the throttle a few times to prine the engine is normal and is not an indication of lack of fuel in the carb. If the carb was empty, there would be no fuel to prime with when you worked the pedal.


Mark...

 

[chichiflys]

Thanks everyone - lots of answers - seems like a variety of possibilities. A cornucopia if you will. I'm thinking it's time to edumacate myself on that carb thingy.

MarkW, the bowl is empty after it sits for several days. Pumping the petal a few times does nothing. I need to crank the engine a while to get the fuel pump to move fuel back into the empty carb to start the engine as PinHead mentioned. So is it normal for the fuel to completely evaporate out of the bowl after a 5 days or so? I don't remember having that problem in my FJ40 a number of years ago.

Of course the "gravity" answer by JackRabbit was pretty ingenious....I have to assume you were implying I need to read up on the details of the carb on a 2F, thanks for the hint. Learning is painful.

BTW the accelerator pump works fine.

 

[Mark W]

I would not expect to see the fuel evaporate in 5 days. Maybe in extremely hot climates. I can leave a rig sitting in the driveway or in the shop for much longer than that and still have plenty of fuel in the bowl.

You may have a leaking plug in one of the passages or a crack in the casting. I really can't think of any other way for the fuel to escape from the carb bowl once it gets there.


Mark...

 

[Pathfinder]

I am having a similar problem as PAFJ. When starting up I have to feather the gas to keep her alive. PAFJ suggested the CB and CO both of which turned out to work fine per FSM. However I did find that my window into the card is leaking fuel. Has anyone had a problem if yes how do you fix? Is there a gasket? I think it is leaking around the area with two screws and that appears to hold the clear glass/plastic lens in place. I think it might be leaking from there. Anyone else had this problem and do you have any suggestions as to what would be proper sealant.

 

[FJ40Jim]

The sight glass has an O-ring behind it. Buy a carb kit, remove sightglass and replace o-ring w/ one from kit.

 

[Pathfinder]

I was told by the previous owner that the carb was rebuilt and I have a detailed quote from a NAPA service center with documents to that effect. Anyway I can purchase just the o-ring for the sight glass without the other stuff? Or am I going to have to buy a whole new carb kit for one o-ring?

 

[NocalFJ60]

What about a leaky power valve? That sits a few mm from the bottom of the bowl on a ledge. The hole in the power valve is a couple of mm from the bottom of the bowl so if just a little fuel is left in the bowl then that could be it. It would leak and drip down into the intake manifold. If this was the case, I think you could replace the springs in the power valve to newer stiff ones that would keep it closed or seal better. Also the power valve could be leaking around where it is screwed into the bottom of the bowl on a ledge and not through the normal hole it flows.

 

[Pin_Head]

It is possible for fuel to siphon out of the primary idle circuit and the secondary transition slot if the air vents for these circuits are plugged (and the fuel cut off in the primary is leaky). These outlets are in the base and are below the level of fuel in the bottom of hte bowl. If the air vents are plugged you may be able to fix it w/o a complete rebuild. Search for "Oklahoma rebuild" for the details.

I never did find out why mine was leaking. I couldn't see any plugs leaking on the outside or inside. I threw in the towel and got another core and rebuilt it and now it doesn't leak.

The power valve is just an auxiliary main jet, so it won't make it leak any more than the main jets.

 

[chitown40]

I am having a similar problem as PAFJ. When starting up I have to feather the gas to keep her alive. PAFJ suggested the CB and CO both of which turned out to work fine per FSM. However I did find that my window into the card is leaking fuel. Has anyone had a problem if yes how do you fix? Is there a gasket? I think it is leaking around the area with two screws and that appears to hold the clear glass/plastic lens in place. I think it might be leaking from there. Anyone else had this problem and do you have any suggestions as to what would be proper sealant.

Make sure your choke is completely closed when you are doing a cold start. The CB and CO will open the choke as needed after about 10 seconds or so. My choke cable stretched or came out of adjustment slightly and it wasn't closing all the way with the choke lever fully pulled out - made for some difficult starts. Also make sure your EGR valve isn't leaking or it will run rough, especially when cold.

 

[2mbb]

I was told by the previous owner that the carb was rebuilt and I have a detailed quote from a NAPA service center with documents to that effect. Anyway I can purchase just the o-ring for the sight glass without the other stuff? Or am I going to have to buy a whole new carb kit for one o-ring?

The parts microfiche shows a part number for the o-ring: 21655-60200. MSRP is $7.34 though!

 

[Pathfinder]

Thats a good point I will do the trouble shooting per FSM. Also glad to know that I can purchase the o-ring for the carb. Thanks I will order from my local toyota dealer.

I will let you know what ends up making the difference, if anything.

Make sure your choke is completely closed when you are doing a cold start. The CB and CO will open the choke as needed after about 10 seconds or so. My choke cable stretched or came out of adjustment slightly and it wasn't closing all the way with the choke lever fully pulled out - made for some difficult starts. Also make sure your EGR valve isn't leaking or it will run rough, especially when cold.