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Has anyone had the problem of fuel running out the carb inlet (Air inlet) into the air cleaner? I posted earlier and thaught it was in the fuel inlet needle or seat. not thinking that now. I think it is in the carb can someone explain the route of fuel into the engine after leaving the float bowl?
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Fuel runs outta carb inlet
- Thread starter randyc
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Nunyas
Yoda
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I had the problem once on my Zenith Stromberg carb. It was right after I finished rebuilding it. I had the float set too low and as a result it just let the fuel keep pumping, and the fuel would puddle up in the throat of the carb. I set the float a bit higher and the problem was fixed. If setting the float height higher doesn't fix the problem for you, then maybe your pump is pushing too much pressure? I've been hearing that if you have more then 4 - 5 PSI then the fuel will just push the valve back open that the float is supposed to close, and cause massive flooding in the carb (possibly draining out into the air filter. I'm not too sure that can happen on a ZS though, because ZS carbs ( on MGBs) are mounted so that they tilt back towards the engine. However, I'm not sure if th etilt is enough to prevent the fuel from dribbling into the air filter assembly. When my ZS flooded out into the throat it wasn't as bad as you're describing.
I bought a kit rebiult the carb tried a .5-4psi electric pump, reset float to close even more, engine will start and run very richly and at idle will stall due to flooding. went back into it and changed the spacers under the inlet needle to make it close more with float travel. I think it will be something simple when and if I find it.
Thank you for your reply and info.
it is greatly appreciated
Thank you for your reply and info.
it is greatly appreciated
Nunyas
Yoda
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One thing to keep in mind when setting the float level on the ZS carb is that you have the carb upside down when setting it. So, to make the float close the valve sooner you'll want to set the height higher (in relation to the gasket surface). Haynes manual says to set the float height to 16 to 17 mm. I believe mine is in the 16.5 to 17.5 range. Another thing to remember is the lumpy side of the float is the top and the "flat" side is the bottom.
Adjusting the float height on the ZS was a royal PITA in my opinion. I think I had to remove and drain the carb around 6 times before I got a good height.
Is it possible that you have something in the valve that's preventing it from fully closing?
Adjusting the float height on the ZS was a royal PITA in my opinion. I think I had to remove and drain the carb around 6 times before I got a good height.
Is it possible that you have something in the valve that's preventing it from fully closing?
Jake is spot on for this one. If the float chamber breather (that line to which he's referring) becomes clogged, then essentially you get air pressure in the float chamber that causes an overflow of fuel. I'd try removing that line and seeing if things start working again (don't plug the hole there, and don't drive like that, because if the fuel starts coming out of there it could be a fire risk).
G
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Guest
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Also you picked a fuel pump with too much pressure. It will force the needle open at that pressure. A SU pump only runs about 2 pounds pressure.
tony barnhill
Great Pumpkin - R.I.P
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4psi's correct.
ok I bought the Haynes carb manual, in the pics im seeing something different than my carb. upon removal of the float bowl (removing screws and lifting bowl off) in the center where the picture shows a "jet" my carb has nothing, and the threaded hole is not threaded in mine, does anyone have or know where I can get a ZS carb for parts or rebuildable? i'm thinking someone has lost the jet with the spring that would be near the brass plug in the bottom.again there is nothing between the brass plug and the needle and the hole is smooth and not threaded, but the manual shows a spring and jet with seals in the hole.
Any and all help is greatly appreciated.
Any and all help is greatly appreciated.
jcatnite
Jedi Knight
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You can check on eBay, I've seen several on there from time to time. Also there are people right here on the forum that probably have some spares laying around. Am I hearing you correctly in that you are saying that the seat for the metering needle is missing? That is a new one on me.
JC
JC
Nunyas
Yoda
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randyc: are you sure you're looking at the correct carb? you should have a 175CD... In the center of the bowl (directly over the brass plug) there should only be a tube. The mixture needle rides (which is attached to the piston up top) up and down inside this tube. There is no jet that goes in there and it should be smooth as you describe. Both of the ZS carbs that I have are like this.
However, there are still some variations even in the ZS 175CD. One of the most notable that I've found is some have an "auto-matic" air by-pass valve while others like my own have a plastic nut with a brass screw in the top... I've seen the nut-screw configuration referred to as "idle mixture" fine adjustment. While the "auto-matic" configuration has been referred to as a temperature sensetive by-pass valve. But I have yet to see a ZS 175CD with a jet matching your description.
However, if you would still like to invest in a parts carb, I'm sure Tony Barnhill may be able to help you, or even eBay. A parts carb can be handy, I obtained mine and used the best parts from both and a rebuild kit to make 1 good carb.
However, there are still some variations even in the ZS 175CD. One of the most notable that I've found is some have an "auto-matic" air by-pass valve while others like my own have a plastic nut with a brass screw in the top... I've seen the nut-screw configuration referred to as "idle mixture" fine adjustment. While the "auto-matic" configuration has been referred to as a temperature sensetive by-pass valve. But I have yet to see a ZS 175CD with a jet matching your description.
However, if you would still like to invest in a parts carb, I'm sure Tony Barnhill may be able to help you, or even eBay. A parts carb can be handy, I obtained mine and used the best parts from both and a rebuild kit to make 1 good carb.
ok mine has the plastic nut and screw on the bypass and it sounds like you are right the only thing above (in the mounted position) the brass plug in my carb is the needle and and the brass/copper tube . only when i look at the haynes carb manual all of the carbs in there show a jet assembly. I still have fuel running out the carb (air inlet) throat. I think im going to try to find a carb. I have practically built the whole car while fighting this carb problem. But I would really like tofind the problem in this carb to satisify my mind.
Nunyas
Yoda
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hah!! I knew I shoulda held out a bit longer! I picked mine up for 750.00 a coming up on 2 years (2yrs in Feb) ago in running condition and driveable... /ubbthreads/images/graemlins/smile.gif
I use the term "driveable" loosely here, but I have been driving it since I got it. /ubbthreads/images/graemlins/smile.gif
I use the term "driveable" loosely here, but I have been driving it since I got it. /ubbthreads/images/graemlins/smile.gif
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Only THREE things I can think of to cause this problem: Delivery pressure too high, a blocked float chamber vent tube... and you've checked the float height and needle/seat to rule 'em out, right? Yeah, I know, that's four. Mia culpa. But that's th' lot, AFAIK.
That thing is a "demand" carburetter: only gets as much fuel as the vacuum in the intake will allow (in essence) into the top chamber over the diaphragm (or piston), raising the progressively narrower needle out from the jet orifice. That jet hole at the point where the air/fuel is mixed (the top) is almost the same I.D. as the size of the needle's O.D. at its shank. The delivery is regulated by the amount of fuel (level) in the bowl, and should when operating properly be somewhere over half way up the jet tube. The float needle and seat should keep that level with the fuel pump on, engine not running. Even without a jet in the tube, that level should not be higher, much less pour gas out the carb inlet. If it passes this "static" test, you've ruled out pressure, float/needle/seat as an issue.
The problem you seem to be describing is with delivery. Either pump pressure is too high, or the float/needle/seat not working properly (or maladjusted). If the fuel *only* pours out as the engine is running (as you've stated), THEN the vent tube will be a "likely suspect" as well. I'd also say: if you have anything other than an SU pump, I'd put a pressure regulator in the supply line between the filter and the carb. Most auto parts houses have an adjustable one on the shelf. Set it low (2~3 lb/sq") and you'll be sure of what the problem is *not*.
Hope this helps "narrow" the possible list of causes, sorry if some of it is redundant.
That thing is a "demand" carburetter: only gets as much fuel as the vacuum in the intake will allow (in essence) into the top chamber over the diaphragm (or piston), raising the progressively narrower needle out from the jet orifice. That jet hole at the point where the air/fuel is mixed (the top) is almost the same I.D. as the size of the needle's O.D. at its shank. The delivery is regulated by the amount of fuel (level) in the bowl, and should when operating properly be somewhere over half way up the jet tube. The float needle and seat should keep that level with the fuel pump on, engine not running. Even without a jet in the tube, that level should not be higher, much less pour gas out the carb inlet. If it passes this "static" test, you've ruled out pressure, float/needle/seat as an issue.
The problem you seem to be describing is with delivery. Either pump pressure is too high, or the float/needle/seat not working properly (or maladjusted). If the fuel *only* pours out as the engine is running (as you've stated), THEN the vent tube will be a "likely suspect" as well. I'd also say: if you have anything other than an SU pump, I'd put a pressure regulator in the supply line between the filter and the carb. Most auto parts houses have an adjustable one on the shelf. Set it low (2~3 lb/sq") and you'll be sure of what the problem is *not*.
Hope this helps "narrow" the possible list of causes, sorry if some of it is redundant.