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  #1 (permalink)  
Old 12-24-2008, 08:26 PM
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Default Fuel leak question

I have been fighting a problem for a while and need someone's help. I have 48 IDAs on a big block with the 10 deg canted intake. Whenever I stop the car after a drive, the heat seems to percolate the fuel and I get dripping out of the accelerator pump jet. It collects in the throat and eventually leaks out of the throttle shaft onto the manifold.

I have a return line on the fuel so it should be immediately dropping pressure when the car is turned off and I have the phenolic gaskets under the carbs.

Any suggestions? Has anyone else seen this problem and can you explain it to me and the solution???

Very frustrated!


Thanks.
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Old 12-24-2008, 10:12 PM
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I also have a BBFE and IDA's and had heat also percolating the sh$t out of them. problem... too much heat under the hood flowing through hood opening heating the bodies of the carbs. The heat is not coming up through intake its the air passing by the carb bodies. Carbs were so hot I could not hold my hand on them. I wrapped my headers, and added angled shroud to back side of rad to through heat down. Really helped out . I have a straight up (not canted) intake with a large opening in the hood, no scoope. So I really had air flow up and alongside carbs. I also plan on shrouding the top of the Rad because alot of air is still flowing up past carbs but fan angled down and wrapping headers really helped
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Old 12-25-2008, 04:15 AM
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Zimmy,
Quote:
I have been fighting a problem for a while and need someone's help. I have 48 IDAs on a big block with the 10 deg canted intake. Whenever I stop the car after a drive, the heat seems to percolate the fuel and I get dripping out of the accelerator pump jet. It collects in the throat and eventually leaks out of the throttle shaft onto the manifold.

I have a return line on the fuel so it should be immediately dropping pressure when the car is turned off and I have the phenolic gaskets under the carbs.
I have exactly the same problem. The biggest problem is that the fuel also drips into the engine and will end up wearing your rings prematurely.
The fact is that the carbs are absolutely cool when I arrive at my garage, even after hard driving, but after about 10 minutes they are hot as hell and and I can hear a boiling noise and gasoline dripping out of the pump jets.
The phenolic spacers help, the return line also, the smallest pump bypass did not, but the problem seems to be the heat emanating from the engine after shutdown and rising around the carbs which heats them up. Also keeping the hood open does not help.
I did build myself a heatshield for one carb in order to see if it would help, but it did not. I am seriously thinking of installing a fan to get the heat out of the engine with a timing device so it will come on when I shut of the engine off and stay on for about 15 minutes. Where to install the fan is what I am thinking about now.
I read somewhere Rick Lake suggesting to install two fans, one behind each side vent. That could be an elegant solution and would also help during hot days and slow trafic to keep things cool.
I am thinking of some type of 5 inch computer fan with low consumption, because if necessary it could stay on longer without draining the battery.

This is right now my only problem with the webers.
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Old 12-25-2008, 08:34 AM
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Eljaro:

I am at least glad to know that I am not alone. I know it isn't heat from running. When I saw this problem again this week after the engine was back in the car (long story) and I went for the first drive. It was 45 deg F outside and the trip was fairly short. I also think that it is heat sink after it is parked a few minutes. I'll keep looking for a solution and will let you know if I find anything.

Happy Holidays.
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Old 12-25-2008, 05:04 PM
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Default try this

if you run an electric fuel pump only turn pump off before you turn your car off, hit the gas pedal a few times to empty some of the fuel out of the webbers.
This used to work for me on a 289 with IDA's I had a few years back.
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Old 12-26-2008, 07:38 AM
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The problem is the fuel trapped inside the pump conducts in the carb body. The carb heats up and the fuel inside the pump conduct has probably some air trapped along the way, which expands with the heat and pushes the gasoline out the pump jet. The pump draws the gasoline from the bottom of the bowl, so a lower bowl level should not be of much help.
I think only shielding or some type of evacuation of the hot air should help.
I am going to try a pair of Muffin type fans mounted behind each side vent and improve the heat-shields I have already made.
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Old 12-26-2008, 09:46 AM
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Starting instructions after hot shutdown of webers. Push gas pedal half way to the floor and hold that position , then turn the ignition key and she will start right up.

May sound to easy a fix but works every time.

The extra fuel that has dribbled and perculated out of your carbs and down the manifold is not enough to hurt your engine or rings if you give the engine more air during these start up conditions.

Buy holding the pedal half way to the floor the throttle plate is half way open allowing the engine to suck in the nesessary amount of air to lean out the hot, rich and vapourised condition found in intake manifold, carbs and heads.

These conditions mainly found after first hour of engine shut-down.

Getting into this habit of start up can be used in all conditions.
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Old 01-27-2009, 10:46 AM
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Any news to resolve this problem?
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Old 02-05-2009, 06:29 PM
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I think that if you set the float levels with the carbs setting FLAT on a workbench and then install them on the engine (angle mount) that the fuel will be level but higher inside the float chamber towards the centerline of the engine because the float fulcrum is on the low side of the carb when it's mounted on the manifold. I don't have the answer but believe a lower float setting is the solution. I think also the fuel would drip from the auxiliary venturis before the accelerator pump jets.
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Last edited by Rick Parker; 02-05-2009 at 08:27 PM..
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Old 02-06-2009, 05:16 AM
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Now that I think of it.. I never had this problem before until I had the carbs off the motor. At that time I readjust the floats. I usually adjust the floats on the motor and never had that problem.

Rick, I do believe you might be right
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Old 02-07-2009, 12:07 AM
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Acknowleging the above, it is also possible that by lowering the fuel level to eliminate the drip issue that the emulsion tube selection may be effected a minor amount. As John Passini the author of 2 great Weber Tuning Guides from the 60's once said about jetting choices... "Suck it and see".

Good luck
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Old 02-23-2009, 01:45 PM
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has anyone any update to resolve this problem?
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Old 02-24-2009, 06:23 AM
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Did those of you experiencing this problem alway have the problem of fuel pouring from the pump jets?

What changed?

Please respond.
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Old 02-24-2009, 05:50 PM
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bump......
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Old 02-25-2009, 09:17 AM
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Yes always dripped after shut down.
Only way i could see it not dripping is if you are running to cold of a thermostat eg) 160 deg.
Maybe thats what changed. Where you running a 160 and then changed to a 180 or 190.
Webers love heat.
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Old 02-25-2009, 09:54 AM
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The carbs are ment to sit level! If they are on an incline with the pump squirter (now lower) towards the inside of the engine the fuel level will be further up in the pump well and may be leaking as you describe. Lower the fuel level.
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Old 02-25-2009, 10:24 AM
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I dont recall my pump jets ever leaking. I have tried shutting down my pump to lower the level a block before shutdown. It still leaks

The only thing in my situation that changed was new pump jets( which I replaced back to the old) and float level (which I lowered before shutdown.

The carb bodies themself are cool to the touch.

Zimmy,

Has your system always leaked?

Eljaro,

Has your system always leaked?

I dont recall other complaining about the leaking from the pump jets.

Rick,
I am not saying you are not correct but it seems something changed to cause the pump jets to start leaking. Or I never noticed it.

One thing, if you block the by pass all hell breaks loose through the pump jets.

Maybe its the fuel?

Just when I think I am moving forwad with these carbs I go 1 step back.
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Old 02-25-2009, 12:13 PM
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A zero bypass valve will most defanetly biuld up fuel pressure in the pump chamber caused buy heating up of the carb body and expanding the fuel which has no place to escape except out the pump jets.

The larger the bypass valve # the more of the pressure biuld up will divert back to the main float chamber, Thus allowing less fuel out the pump jets during pressure build up from shut down heat sink of carb body.

Yes your carb body will be cool to the touch after shut down.
Check how hot they are 10 minutes later.

The pump Jets are not affected by the angle the carbs are on because they are fed by an inlet located at the bottom of the main float chamber.
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Old 02-25-2009, 12:18 PM
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Quote:
Originally Posted by carmine View Post

The pump Jets are not affected by the angle the carbs are on because they are fed by an inlet located at the bottom of the main float chamber.
Is there anyone that has a 10 degree intake that does not leak.

"This thing is driving me nuts!!! I dont ever remember mine leaking"
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Old 02-25-2009, 12:24 PM
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I think they always leaked and you never noticed it.
More so now that you have a #0 bypass valve.
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