A month or so ago I commented that I was seeing some hesitation coming out
of turns when I was autocrossing. Jerry Mouton suggested the mixture may be
rich. Well, not only is it rich, the car is actually running gas out the
bottom of the air filter canister.
It appears the rear zenith has a problem shutting off the gas flow and I’m
having a problem figuring out a solution. When I turn the key on but don’t
start the car, the pump clicks and then stops as it should. If I raise the
cylinder in the carb, gas rushed up out of the hole the needle moves up out of.
After I do this the first time, the gas continues to leak, even when I lower
the cylinder.
I thought that replacing the float valve would take care of the problem.
Nope. A new valve, as a matter of fact, two new valves, and it still kept
leaking. I then thought maybe my float is leaking and not raising up to shut
off the gas. Nope. I replaced the float with two other float assemblies and
the carb still wants to leak. What can I do next? I may actually remove the
bowl and turn the key on so I can manually raise and lower the float to see
if there might be another reason the darn thing keeps leaking. I’ve checked
the float level and it appears to be correct. I do know it is identical to
the front carb that does not appear to be leaking.
At least I’ve apparently determined why the car has a richness problem. I
just don’t seem to know how to solve it.
Help, please. I wanna go autocrossing again next weekend.
Dave,
Barring something bizzare like a cracked carb casting, which is
exceedingly unlikely, it can only be a leaking or mis-adjusted
float valve, or a bad float. If fuel continues to pour out of the
carb jet when the piston and needle are removed, and the fuel pump
turned on, is a positive indication that the fuel level is too
high. Fuel should not flow out the jet when the piston and
needle are removed. So, I would first make sure the new float
valves actually seal properly by simply inverting bolw covers, and
blowing into the fuel inlet fitting. If they are sealing OK then
your float levels are off, and I’d just adjust them down in 1/16’’
increments until the fuel stops pouring in.–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
It can only be a leaking float valve or bad float, unless it’s a
punctured diaphragm. Take the carb off and disassemble it.
Mike Frank
How about a punctured diaphragm?At 06:09 PM 6/4/2005, you wrote:
Barring something bizzare like a cracked carb casting, which is
exceedingly unlikely, it can only be a leaking or mis-adjusted
float valve, or a bad float.
In reply to a message from Mike Frank sent Sun 5 Jun 2005:
I had this very same annoying , dangerous, knuckle scraping problem
with the front left carb on my V-12. After removing the carbs 15
or 16 times, fiddling with the floats, valves, etc., I decided to
test them on my workbench before re-installing them.
This is what I did and it eventually worked for me. Let me say
first, that you cannot use the factory float settings as set in
stone. I say this because I found the the height of the needle
shutoff valve {that I replaced} was not the same height as the
original one.
remove carb, drain the fuel, remove float cover. Since the carb
is still leaking fuel, I would re-adjust the float height ever so
slightly as Ray suggested.
I would then attach an electric fuel pump with a benign fluid {I
used windshield washer fluid} to the inlet side of the carb. I
used a 5 psi pump [which is slightly higher psi that needed} and
let the pump run for a 1/2 hour or so. If you still ar experiencing
leakage, you again need to re-adjust the float height so it closes
earlier. If after all this is not successful, I would most likely
ship off the carb to someone professional like Joe Curto. If you
want to just test whether or not the float valve is even shutting
off the fuel, you can performe a similar bench test as follows:
Remove the float cover. Turn the carb upside down. Turn on the
fuel pump with the same windhsield washser fluid, and observe if
the needle valve is allowing any fluid past it’s seat. The carb
must be level.
In reply to a message from Mike Frank sent Sun 5 Jun 2005:
Mike,
I don’t see how a leaking diaphragm can cause fuel to pour
through the jet as he described. Cause a leak? Sure. But not
pour fuel through the jet? I don’t see it.–
The original message included these comments:
It can only be a leaking float valve or bad float, unless it’s a
punctured diaphragm. Take the carb off and disassemble it.
Mike Frank
–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Ray Livingston sent Sun 5 Jun 2005:
While on the subject of bad diaphrams, I had to replace 2 ‘‘new’’
diaprhams on my ZS carbs. The pistons simply would not elevate
correctly. It is also important the the rubber ‘‘tab’’ be properly
indexed on the carb body.
It seems the floats are letting to much gas into the chamber.
The gas has no place to go but come out somewhere, like the
needle jet assembly, which is located in the middle of the
float bowl.
Walter--
The original message included these comments:
start the car, the pump clicks and then stops as it should. If I raise the
cylinder in the carb, gas rushed up out of the hole the needle moves up out of.
After I do this the first time, the gas continues to leak, even when I lower
the cylinder.
–
Walter Schuster 78XJ6LFI Ser.II, 69Eser.II 2+2
Albuquerque/New Mexico, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Ray and others suggested a solution to my gushing gas problem - set the
float level a bit lower than the manual. I’ve tried to set the floats per the
manual over the years. Apparently something has changed that has made it
necessary to set the float a bit lower than what I have done previously. I dropped
the float level by 0.063" and no more gas running out of the carb. I went
ahead and set the front carb lower as well. I hope that’s all it takes to
solve the flooding issue.
Thanks to all that sent suggestions. What a great list!!!
Now it’s back to getting ready for the autocross this coming weekend.
