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Carbs again?

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C

Crisis

Jedi Hopeful
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I have had a "wet" carb issue for some time now and the wife has banished the TR6 (73)to the backyard shed from the attached garage. Apparently some people don't like the smell of raw gas?
Took another stab at it yesterday; removed, cleaned, set floats, tested vent chamber valve,removed and cleaned choke,checked needle adjustment apparatus. Put everything back together, adjusted air and mixture. Thought I had it; no leaks in driveway, no misfires etc. Went for short drive and all of a sudden its a dog! Ok under acceleration, but not cruising or idling. Got home, popped the hood, and saw that body metal crease just under the carbs full of gas-pooling. Even after stopped for awhile it continued to drip. The I noticed it was dripping from the vent chamber hose which goes to the carbon canister. I detached the hose at the carb, lowered and turned upside down and gas poured out! BTW, the air filter on that carb was also soaked. When cleaning etc., I checked that at idle the valve from float chamber to air filter vent hole was plugged as it should be (sucking and blowing on hose fitted into vent hole).
My guess is gas was being sucked into canister hose at idle and into air filter vent off idle. Doesn't this only mean that the float and/or float valve are not working and the float chamber is full? Tested perfectly off the car?
Sorry for being so long winded, and appreciate any ideas you may have. Got to get this car back on the playing bench (attached garage) and out of the locker room (shed).
 
I would say from my experience that either the float has gas in it or the float valve is no seating properly. Since you have checked the float then I would look at replacing the float valve. It runs good under acceleration because the gas is being used up rather than floading the engine.
 
Yup, fuel in canister means the float chamber(s) overflowed for some reason.

Just a thought, since it was fine and went bad again ... How's your fuel filter ? Has the soft line between the filter and the carbs been changed in the last few years ? One possible explanation might be crud in the fuel blocking the float valves open. Don't know if you get gasahol up there or not, but even without it, the soft fuel lines need to be changed every 10 years or so.

Another thing to look at (if none of the above pans out) is fuel pressure. ZS carbs won't hold back much, so if it's too high for some reason ...
 
Randall,
I agree, the float chamber must be filling up. But why when I have the thing apart in my hands does it work perfectly? What would a LBC mechanic have done in the car's day? Replace the valve and see what happens? I guess that is what I'll have to do.
Thanks for your help.
 
Randall points to the many "usual suspects". Especially if its only one carb acting up.

Has any of these events coincided with a new fuel pump? I've seen three, in as many weeks, on Spitfires that were pumping 6psi! All had the same new aftermaket pumps.

I've seen some of the needle float valves stick open with ethanol "enhanced" fuel. The gross jets don't mind it though. It must have something to do with the type of plastic around the needles on some of them. This particular problem is one that I've seen on SU's more than ZS's though.
 
In my case, it turned out to be the little connector lines at the carbs, that although they looked fine outside, were shedding bits into the fuel. First time I just pulled over and cleaned the float valves (really easy on SU carbs). Second time I did it again, then changed all the soft lines when I got home. That cured it.

But the ZS float valves don't come apart (at least the ones on my Stag didn't), so I had to change them when they started acting up. Likely still crud that got in somehow, but I couldn't get it out of there.
 
swift6 said:
Has any of these events coincided with a new fuel pump? I've seen three, in as many weeks, on Spitfires that were pumping 6psi! All had the same new aftermaket pumps.


Swift6, I just installed a new pump on my 78 Spit. Is there anything I need to look for re: pressure being too high?
I took her for a test run last night and she ran great.

Also I was advised not to re-use the spacers so I ditched them, then the problem was no enough thread on the studs for the nut to tighten it all down. I improvised by adding 4 flat washers on the other side of the pump thus keeping the nuts on good thread.
Click to expand...
 
Your best bet is to actually measure the PSI the new pump is putting out. Should definitely be under 3psi.
 
Just wanted to close off this thread by reporting that I seem to have solved my leak problem (touch wood). The float chamber was indeed flooding due to what appears to have been a stuck pin in the valve. It appeared to work fine when I had it apart, however, by replacing it with a new gross jet (all I could find locally) I now have dry carbs. I also lightly sanded the choke body as it didn't seal too well with the carb body.
Thanks for all your help.
 
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