Leaking Webers - Alfa Romeo Bulletin Board & Forums
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post #1 of 13 (permalink) Old 05-29-2019, 01:06 PM Thread Starter
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Question Leaking Webers

Hey guys, I have been having some issues trying to tune my dual webers.
I recently replaced my head gasket, now I am tuning the fuel system. Before I had to replace the head gasket, the carbs were leaking a bit of fuel out. Now, they are much worse.
Ive taken them off and synced the throttle bodies. Ive cleaned the jets in parts cleaner. I attempted to set the floats, but here lies my issue.
If I turn the key and prime the fuel pump and wait a minute, fuel dumps out of the carbs on the intake side-a lot. It will do this on both sets of carbs, but the left/rear most is the worst.
These are weber 40DCOE151 carbs. They do not appear in bad shape, I was going to adjust them with the uni-sun yesterday but it seemed like the fuel leak was only getting worse and worse.

What could be causing this leak?
When I attempt to test float bowl level, I start the car, idle for a few seconds, shut off, take out both main jets, then stick in my caliper for measurement. Correct bowl from the rim of the jet is 29mm +/- .5 correct?
To adjust the floats, I measured 12.5mm from the float to the gasket on the rim from the furthest point on the plastic float (end that travels the most). Then 25mm from the center of the float to the gasket for the most open point.

What did I miss? I am completely new to carbs, I understand the general aspect of how they work but this is my first go at setting them.

I did use a drill bit to measure the close position on the float.

I cleaned the little mesh filter in the caps.
If I test the floats off the car, I can close the float and blow through the tubes, and it will stop-no leaks from what i can find.

Aaron
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post #2 of 13 (permalink) Old 05-29-2019, 01:46 PM
Richard Jemison
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Webers leaking

Well, hopefully it`s as simple as too high a fuel level in the carbs. This can be caused by too high fuel pressure. Fuel pressure over 3 lbs will cause it.

Don`t rely on a pressure regulator as when fuel is "deadheaded (no outlet for fuel with the pump running and needle valves closed in the carbs) pressure WILL rise. Get a proper low pressure pump. I use Airex pumps, designed for Onan generators. (Ebay or Amazon) under $30.00

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post #3 of 13 (permalink) Old 05-29-2019, 08:17 PM Thread Starter
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I checked under my car to see what fuel pump is mounted, I found this generic from eBay-
https://www.ebay.com/itm/Universal-S...4383.l4275.c10

It says its rated 2.5-4 PSI, from what I can see its non adjustable, so who knows what pressure it is actually pushing out.
Looks like the fuel pump is a good place to start.
The pump looks brand new out of the box, so my bet is that the previous owner put it on not too long before I bought the car.

Aaron
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post #4 of 13 (permalink) Old 05-29-2019, 09:07 PM Thread Starter
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To correctly run webers, do I need to change the fuel pump to a pump that is 3.5 PSI at max?
Or do I need a fuel pressure regulator to bring down the pressure? Or both?

Currently the system is completely deadheaded, no tank return.

The issues that have made me jump into this are the leaking and when I was trying to adjust the mixture screws the other night, some screws changed the engine significantly and others did not seem to affect the idle at all. Thats what drove me to dive into checking float setup.
Then after adjusting the floats, my fuel dumps everywhere (worse)

Aaron
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post #5 of 13 (permalink) Old 05-30-2019, 06:09 AM
Richard Jemison
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Fuel level

Quote:
Then after adjusting the floats, my fuel dumps everywhere (worse)
Drop the fuel level 1/8 inch from where you have it now. That is 1/8" more space between the top of the floats and the top gasket.

Easy way to avoid the "deadhead" issue is to put a "T" in both the feed line and the output line close to the pump. Run a hose between the two, but put a restrictor in the line with only a .040 (1mm) hole in it to maintain pressure to the carbs. The tiny orifice will reduce the pressure spikes from the pumps delivery.

Excess fuel is not just running out of the carbs it`s running into the cylinders!
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Last edited by Alfar7; 05-30-2019 at 06:14 AM.
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post #6 of 13 (permalink) Old 05-30-2019, 08:01 AM
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Filter King regulators will hold the set pressure even when they are dead headed.

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post #7 of 13 (permalink) Old 05-30-2019, 09:29 AM Thread Starter
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Quote:
Originally Posted by alfaparticle View Post
Filter King regulators will hold the set pressure even when they are dead headed.
So I can plump in the filter king filter without a fuel tank return? Its a strong enough regulator to put back pressure on the pump instead of re-routing excess fuel?

Aaron
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post #8 of 13 (permalink) Old 05-30-2019, 09:39 AM Thread Starter
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Quote:
Originally Posted by Alfar7 View Post
Drop the fuel level 1/8 inch from where you have it now. That is 1/8" more space between the top of the floats and the top gasket.

Easy way to avoid the "deadhead" issue is to put a "T" in both the feed line and the output line close to the pump. Run a hose between the two, but put a restrictor in the line with only a .040 (1mm) hole in it to maintain pressure to the carbs. The tiny orifice will reduce the pressure spikes from the pumps delivery.

Excess fuel is not just running out of the carbs it`s running into the cylinders!
What could I use as a restrictor though??

Aaron
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post #9 of 13 (permalink) Old 05-30-2019, 10:27 AM
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You don’t need a return line. Just a proper pressure pump, or a pump and inline regulator. Dead-heading carbs isn’t a problem provided your pump setup is correct.

Before messing with your pump, make sure your float levels are actually correct and your needle valves aren’t leaking.

If you’re worried about pressure suggest also measuring what you’ve got with a gauge before swapping parts. Most car parts stores will rent you a gauge.

Tom

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post #10 of 13 (permalink) Old 05-30-2019, 10:27 AM Thread Starter
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It doesn't look like there are too many Filter King regulators available in USA, they are all UK?
Could I use a Holley adjustable Fuel regulator that does not have a fuel return?

Aaron
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post #11 of 13 (permalink) Old 05-30-2019, 10:32 AM Thread Starter
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Quote:
Originally Posted by Gubi View Post
You donít need a return line. Just a proper pressure pump, or a pump and inline regulator. Dead-heading carbs isnít a problem provided your pump setup is correct.

Before messing with your pump, make sure your float levels are actually correct and your needle valves arenít leaking.

If youíre worried about pressure suggest also measuring what youíve got with a gauge before swapping parts. Most car parts stores will rent you a gauge.
Thanks, ive done regulators and adjusted these sorts of things on cars before, just never a car that was A. Deadheaded and B. converted to carbs.

Thats what I was thinking, I can rent a gauge and check it.
I washed out the tops of the carbs where the float receives fuel, there was crud in there so I thought maybe that was pushing the float open. But when I tested the float off the car, it wouldn't leak past the needle valves and they looked to be in great shop-basically new(though it could be the issue).
These are spanish webers, so I doubt the parts are all that worn. They look close to new. (again, could still have broken parts, just wouldn't be my first guess).

Aaron
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post #12 of 13 (permalink) Old 05-30-2019, 10:46 AM
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Buy this Filter King on e-bay. Mount it up front by the Webers, adjust for 3#. Problem solved.
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post #13 of 13 (permalink) Old 05-30-2019, 12:05 PM Thread Starter
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Filter is on the way!

Aaron
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