'74 bus, carb leaking

Carbs & F.I.

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whc03grady
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Re: Carb Leaking

Post by whc03grady » Sun Nov 04, 2012 4:51 pm

Aaaaaand it's leaking again. Gas all over.
Ludwig--1974 Westfalia, 2.0L (GD035193), Solex 34PDSIT-2/3 carburetors.
Gertie--1971 Squareback, 1600cc with Bosch D-Jetronic fuel injection from a '72 (E brain).
Read about their adventures:
http://www.ludwigandgertie.blogspot.com

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Amskeptic
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Re: Carb Leaking

Post by Amskeptic » Sun Nov 04, 2012 7:47 pm

whc03grady wrote:Aaaaaand it's leaking again. Gas all over.
Technical Forum here. Either add this update to the original thread, or state the vehicle in the subject header with a little history for continuity's sake.

See, I think I remember that you had a little springy float retainer under the pin, which you corrected. OK, good, did you check the float level after re-positioning it? Because if you changed the height of the pivot point (you did), you *must* recheck the float level. It should be 13mm under the edge of the carburetor.

Also, were these carbs rebuilt by Others?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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whc03grady
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Re: '74 bus, carb leaking

Post by whc03grady » Sun Nov 04, 2012 9:37 pm

No I didn't check the float level. I'm afraid the Bentley isn't especially helpful either. What if it's off? Fit a different washer to the float valve? Okay, then what? Fill the case with gas again if it's wrong? I don't understand what, exactly, I'm to do. It's a bit like belling the cat.

These carbs were rebuilt by keifernet.

Any truth behind the suspicion that an electric fuel pump can put out too much psi for the float valves--which some say can be wrecked by as little as 2 psi? Where do you get an adjustable pressure regulator that goes down to 1.5 psi anyway?
Ludwig--1974 Westfalia, 2.0L (GD035193), Solex 34PDSIT-2/3 carburetors.
Gertie--1971 Squareback, 1600cc with Bosch D-Jetronic fuel injection from a '72 (E brain).
Read about their adventures:
http://www.ludwigandgertie.blogspot.com

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SlowLane
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Re: '74 bus, carb leaking

Post by SlowLane » Mon Nov 05, 2012 1:57 pm

Any truth behind the suspicion that an electric fuel pump can put out too much psi for the float valves--which some say can be wrecked by as little as 2 psi?

Don't know about "wrecked", though if some have had that experience, I'm not about to argue. Certainly the needle valve can be overcome by excessive pressure and flood the float chamber, but I don't know about long-term damage. I rather suspect that age and fuel composition would have a larger role in needle material wear or decomposition.
Where do you get an adjustable pressure regulator that goes down to 1.5 psi anyway?
Here's one such: http://www.holley.com/12-804.asp.

And here's another that is commonly sold to the aftermarket VW "kiddies": http://www2.cip1.com/ProductDetails.asp ... C-C10-5622

The Holley is probably your better bet, for quality.

Keep in mind that this type of regulator is a "deadhead" type, as opposed to a "bypass" type. The chief difference is that the deadhead type doesn't provide absolute regulation, but rather simply provides an adjustable pressure load between the fuel pump and carburetors. As such it serves to reduce the pressure being supplied from the pump by the amount you set it to, not to the amount. Your success with this type of regulator is dependent on the consistency of pressure supplied by the pump itself over the expected range of delivery volume.

Example: say your pump provides 2 psi of pressure at the maximum flow you require. You set your deadhead regulator to "resist" the pump's efforts to the tune of 0.5 psi, thereby making your needle valves happy with 1.5 psi. But if the pump's pressure goes up to maybe 3 psi as the required flow decreases, like at idle, then the pressure seen by the needle valves would also rise, to 2.5 psi. So you really need to find out how well your pump regulates pressure by itself before slapping on a reducing regulator.

A bypass regulator is one that has a return line to the fuel tank, and is therefore able to regulate to an absolute reference (typically either atmosphere or manifold vacuum). The L-Jet and D-Jet FI systems employ this type of regulator, albeit at higher pressures than any carb would want, but Holley also makes bypass regulators for carb applications. The problem in using one on your bus, of course, would be in plumbing in the return line to your tank.

It also sounds as if you could benefit from the electric fuel shut-off that Colin and some other fellows were chatting about a couple of months back.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Amskeptic
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Re: '74 bus, carb leaking

Post by Amskeptic » Mon Nov 05, 2012 8:37 pm

whc03grady wrote:No I didn't check the float level. I'm afraid the Bentley isn't especially helpful either. What if it's off? Fit a different washer to the float valve? Okay, then what? Fill the case with gas again if it's wrong? I don't understand what, exactly, I'm to do. It's a bit like belling the cat.

These carbs were rebuilt by keifernet.

Any truth behind the suspicion that an electric fuel pump can put out too much psi for the float valves--which some say can be wrecked by as little as 2 psi? Where do you get an adjustable pressure regulator that goes down to 1.5 psi anyway?
It is in the Bentley, idle the engine, take off the top, measure from carb body to fuel level, I just did it to Chloe three hours ago.

I think you might want new needle valves. They are so over the map as far as quality. I just replaced mine to get rid of all of my rich cylinder-wall-wrecking rich starts and fuel drool off the carbs at hot engine shutdown. My new needle valve from the kit I used last October has been leaking under heatsoak since May. I refused to believe it was not working correctly, so I have been crabbing and looking for "fuel shut-offs". Well, new parts have bitten me again, to which I say, " !*@#$&%".

Now Slow Lane cannot be expected to know that the dual carb buses call for 3-5 psi, right in the range of your electric pump. If both of your carbs were/are leaking, OK check fuel pressure mitigation strategies, but if only one carb is the bane of your existence, it suggests a specific individual part failure.
ColinChloeStillKicksMyAssEveryDay
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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