Weber IDF carbs leaking fuel when hot

[riverside66]

So I'm dealing with a couple of issues with my new rebuilt T4.

One of them is that, when the carbs get hot, they leak fuel. It seems that the leak may be from the throttle shaft in the middle. I can reach around the side and touch a shop towel to the accelerator pump shaft, and it will be lightly wet with fuel. I've already checked the accel. pump diaphragm and it's not leaking from there.

I noticed this a couple of weeks back, when I first started driving around the neighborhood while getting the carbs dialed in. I added phenolic spacers and that seemed to do the trick, however yesterday I took the bus on the highway for the first time and the engine got hotter than it had before.

While driving, the carbs don't get hot. But after a drive, and then parked, the heat travels up the intake manifolds and that's when the carbs get hot and the issue happens.

I've searched quite a bit, and can't seem to find anyone else with this issue. Does anyone else experience this? Are these carbs defective, or is there a solution for this problem?

I got 1/4" spacers. I guess I could get thicker spacers, but before I go ordering anything else I just wanted to see if any of you have any input.

Thanks!
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1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-

[aeromech]

Alcohol in the fuel probably
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[riverside66]

[busman78]

Are they actually heat resistant phenolic? The good ones will set you back about $35 per intake (pair). Is the fuel line touching the engine or other hot source?

[riverside66]

[riverside66]

I'm thinking maybe adding the thick intake manifold gaskets (between the intake and the head) will help. Like these: http://www.jbugs.com/product/022129707F.html. Right now I'm only using the thin paper ones.
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1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-

[busman78]

Have you removed the air cleaners to actually look down the bore? Can you see the fuel drip out? Boiling fuel also gurgles, the intake gets hot enough so the dripping fuel vaporizes on contact which will hiss, does the intake feel hot enough to do that? Can you hear a hiss?

If the fuel is 10% Ethanol it has a 20-30 degree lower boiling point than regular unleaded, but if the carbs are getting hot enough so you can not touch them after shut down you will probably boil or heat up enough the regular unleaded fuel to push out of the bowl.

Try some 100% unleaded, if available where you live. Cheap test.

[aeromech]

[riverside66]

Thanks for the link and info Gary.

My carbs are new, but either way this just reinforces the idea to use ethanol free gas. Luckily I have many options for that around town here, and I'll try that with my next fill up.
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1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-

[aeromech]

Let's see some pictures

_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[richparker]

Athough I do not get very much carb soak, it is a problem pretty much everyone deals with. After a long hot run I’ll let my bus idle for a minute or so, my theory this gives the heads some time to cool a bit before shutting it down. Is my theory correct? Probably not but it has been working for me. I’m using ethanol gas and I do not have the spacers.

Since your engine is new it will run hotter until it breaks in. Good luck.
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[busman78]

I always use a thick manifold to head gasket, they are a little over 1/16", the one I have here measures at .067" thick.

[riverside66]

I added thick gaskets at the bottom of the intake manifolds, like these --> eBay this morning. They're a bit thicker than 1/4". Went for a drive today, and roughly 20 minutes after parking I went out to see if there was fuel leaking from the carbs. There was.

So I shot this video to show what is happening:

Link


Anyone seen anything like this? What can I do to stop this from happening?

The outside of the carbs doesn't feel that hot. I certainly wouldn't think they are hot enough to boil fuel.

I did recently add ethanol free fuel, however I was only about 1/2 empty (filled up 8.84 gal) so I suppose this test is still in progress...

This is pretty frustrating (and unsettling).
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1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-

[Lil Lulu]

How long since new gaskets were installed? Have the floats been set properly? Could the throttle bushings be worn out?

Just a few thoughts.
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'72 Deluxe - Niagara Blue w/pastelwiess Camper Special 2L dual 40 Webers 002

'74 Hightop Weekender "Dixie" 1800 34 Del singles

[aeromech]

You know, you actually want those manifolds to warm up. That’s a big cause of rough running is carbs without preheat.

What’s up with that brake booster vacuum line? I see the fitting on the intake manifold and the hose connected to it but the routing to the hard plastic line with the check valve seems off. Also, I’d ditch the hard line and install gates brake booster vacuum line instead.

Your fuel leak does seem like it’s coming from the throttle bushing but your carbs look new so that’s a mystery
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[aeromech]

So you have a facet electric pump installed on your firewall instead of up underneath the bus where it’s safer. Then you have have the fuel line running to a glass bowl strainer (not safe) and then going to the carbs without any fuel pressure regulator. I see a clean looking installation that’s poorly conceived.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[riverside66]

[riverside66]

[riverside66]

Gary,

I appreciate the feedback, and after thinking about what you said, I realized that from the pump to the carbs (I guess more specifically, from the FPR) fuel travels downhill. Perhaps this has nothing to do with fuel boiling over, but maybe the bowls are just being over filled aftert the pump shuts off and it loses vacuum?

I'm going to install the Carter pump, and redo the fuel lines. Do you have any photos of how you've run fuel lines on a similar build?
_________________
1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-

[riverside66]

It's been over a year since my last post, and at long last, I have an update. I really began to doubt my fuel delivery setup after Gary's feedback. So I decided to finally scrap the old Facet pump, hook up the Carter rotary pump, and design a new route for the fuel lines, using mostly 5/16 hard line, and AN fittings for connections (and getting rid of the fuel shutoff valve/s). I mounted the Carter pump (not shown) in the factory FI pump location, and was even able to make use of the old FI hard line mounting clips under the bus for the new line I installed.

Here are a few of the photos I took along the way:

Firewall repainted, and new Holley regulator installed.

Firewall back in the bus.

Hard line connected. 5/16 line, and -6AN fittings. About 6" of Gate Barricade hose from the carbs to the hard line that you can't see (to absorb engine vibrations).

Closer shot.

Everything back in, and in its place.

As nice as the new lines are, my fuel leak issue persisted (fuel leak from the carb, around where the acc pump spring is). This time however, I realized that it wasn't just when they were hot. They leaked after the engine shut off from testing, before the engine had a chance to get that hot. I could hear a faint gurgle sound coming from the leaking carb after turning the engine off. But, shouldn't the float stop the fuel?

So I took the carbs off, and measured the floats. One was at 10mm (juuust resting against the needle), and the other was at 12mm. I made the mistake of not checking these measurements myself when I first got them (I wrongly assumed they had already been set). Using the instructions I received from a Weber Redline gasket/rebuild kit, I set the upper float position to 14mm. I set the lower at 21mm (FYI: this is a deviation from their instructions. They advise for a 2mm needle drop). I'm happy to report that after reinstalling the carbs, taking a thorough driving test, and checking for fuel leaks after letting the engine park/rest, I no longer have any fuel leaks.

I really wanted to make sure I posted this update, as there are many threads started with similar issues, but so so many of them never have any resolution updates.

So, all said and done, it looks like the leak issue had little to do with my fuel routing, and much to do with poor float settings. But hey, I like the new fuel delivery setup much more. The Carter pump is way quieter than the Facet, the hard line and Holley regulator look dang nice, and I also took the time to install a proper pump shutoff module (this one: https://revolutionelectronics.com/Products/Fuel_Pump.html.
_________________
1977 Standard Beetle -Sold-
1979 Transporter - "Wheatbread" -Sold-