i'm finding the fuel in the carby bowl is empty after about 3 or 4 days of sitting (grey motor)
cant find any leaks external and can’t detect any looking down the barrel, the drain & jet plugs are tight.
Any suggestions on where the fuel could be getting out ?
Bowl Evaporation Help
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Marty K Bird
- Posts: 249
- Joined: Tue Oct 02, 2012 5:01 am
- State: NOT ENTERED
- Location: Harden-Murrumburrah NSW
Re: Bowl Evaporation Help
Id hazard a guess at somewhere from the fuel pump back towards the tank .... yeah i know sounds obvious don't it lol.
It could also be getting out under the lip of the bowl but you wont see it because in this weather it evaporate off pretty quick.
The braided line going into the fuel pump or its connectors are another area id check as it might be cracked under that braid.
It could also be getting out under the lip of the bowl but you wont see it because in this weather it evaporate off pretty quick.
The braided line going into the fuel pump or its connectors are another area id check as it might be cracked under that braid.
Re: Bowl Evaporation Help
G'day Robin,
I'm guessing
a) that you've had the air horn off the carb after it's sat for a few days, and can see the bowl is dry, and
b) that the carb doesn't dry out immediately (say 1-2 hours) after a run, which would indicate percolation (boil out from engine heat).
The BXOV Strommie carb is atmospherically vented - the fuel bowl is connected to the carb throat, which can then breathe via the air cleaner. If they sit for an extended period of time, they will evaporate out (mine typically does it after about a fortnight of sitting). 2-3 days is quick though.
Most of the time a dry bowl is caused by an external leak - either of the two bowl plugs is usually the culprit. It will evaporate quick, but you can normally see (and smell) it.
The carb will normally not leak down the throat, as most of the "outlets" are above the height of the fuel bowl level (ie fuel would have to flow uphill). The exception to this is the idle system, where the idle discharge holes are lower down in the carb throat than the fuel bowl. This means that the carb can syphon the fuel bowl via the idle holes. They are down low in the throat, and can be hard to see if they are slowly syphoning. The carb design uses the idle air bleed as a syphon breaker to stop this syphoning. The idle air bleed is located at the joint between the air horn and throttle body. You can see a little channel if you look down the throat (see p44 of the Guide for a photo with lots of red arrows). If the idle air bleed is blocked with carbon, it will allow syphoning (and hence an empty bowl).
The painful bit is that the idle air bleed is fine (#52 drill or 0.0635”), and is buried in that little channel. You can't get a straight shot with a pin or bit of fuse wire to rod it out, even with the airhorn removed. The only real way to get at it is to pull the carb apart, soak in thinners and blow it with compressed air. You may be lucky and get it to clear with the "hand over the carb throat" trick, but it's unlikely (it tends to just suck harder on the idle tube rather than clearing the idle bleed). You could drill out the plug and rod it out from the outside, but there is a big risk of getting swarf into the carb (and noone sells the plug to replace ithe drilled out one with anyway).
Cheers,
Harv (deputy apprentice Stromberg fiddler).
I'm guessing
a) that you've had the air horn off the carb after it's sat for a few days, and can see the bowl is dry, and
b) that the carb doesn't dry out immediately (say 1-2 hours) after a run, which would indicate percolation (boil out from engine heat).
The BXOV Strommie carb is atmospherically vented - the fuel bowl is connected to the carb throat, which can then breathe via the air cleaner. If they sit for an extended period of time, they will evaporate out (mine typically does it after about a fortnight of sitting). 2-3 days is quick though.
Most of the time a dry bowl is caused by an external leak - either of the two bowl plugs is usually the culprit. It will evaporate quick, but you can normally see (and smell) it.
The carb will normally not leak down the throat, as most of the "outlets" are above the height of the fuel bowl level (ie fuel would have to flow uphill). The exception to this is the idle system, where the idle discharge holes are lower down in the carb throat than the fuel bowl. This means that the carb can syphon the fuel bowl via the idle holes. They are down low in the throat, and can be hard to see if they are slowly syphoning. The carb design uses the idle air bleed as a syphon breaker to stop this syphoning. The idle air bleed is located at the joint between the air horn and throttle body. You can see a little channel if you look down the throat (see p44 of the Guide for a photo with lots of red arrows). If the idle air bleed is blocked with carbon, it will allow syphoning (and hence an empty bowl).
The painful bit is that the idle air bleed is fine (#52 drill or 0.0635”), and is buried in that little channel. You can't get a straight shot with a pin or bit of fuse wire to rod it out, even with the airhorn removed. The only real way to get at it is to pull the carb apart, soak in thinners and blow it with compressed air. You may be lucky and get it to clear with the "hand over the carb throat" trick, but it's unlikely (it tends to just suck harder on the idle tube rather than clearing the idle bleed). You could drill out the plug and rod it out from the outside, but there is a big risk of getting swarf into the carb (and noone sells the plug to replace ithe drilled out one with anyway).
Cheers,
Harv (deputy apprentice Stromberg fiddler).
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.
Re: Bowl Evaporation Help
Thanks Guys this has given my some food for thought
the fuel level is droping way lower than the inlet valve, the idle air bleed sounds likely the closest cause of the problem
i'll arm myself with the strommy guide and do some pokin around
Rob.
the fuel level is droping way lower than the inlet valve, the idle air bleed sounds likely the closest cause of the problem
i'll arm myself with the strommy guide and do some pokin around
Rob.