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Fuel pump / carburetor fuel cutoff cut off valve when used?
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easy e
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PostPosted: Fri Jan 27, 2017 2:05 pm    Post subject: Fuel pump / carburetor fuel cutoff cut off valve when used? Reply with quote

Sometime the idle-cutoff solenoid was introduced on the side of the carb... and kept the engine from running on after shutoff.

There was also the anti-siphon valve... maybe the predecessor to the idle cutoff solenoid? Or, were there engines that ran both?

I don't know if the anti-siphon valve was used on beetle only or beetle, bus, ghia...

I think '66 came out with the square topped fuel pump with four screws... but not sure.... and I think that had some sort of modification that stopped engine run-on?
EDIT: found this poking around:
Eric&Barb wrote:
Round shape top is 40 HP thru early 1500.

Pentagon shaped top is late 1500 thru 1600.


So, for the round top, single screw on top (screw inlet) fuel pumps... when & on what... was the anti-siphon valve used? (40hp, 42hp, 44hp?) Part no. 113127405

I think the screw in anti-siphon valve ended (obviously with the end of the screw inlet fuel pumps).... totally disappeared for a while... and then a slip-fit one appeared in 1970.

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Last edited by easy e on Fri Jan 27, 2017 11:28 pm; edited 1 time in total
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busdaddy
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PostPosted: Fri Jan 27, 2017 4:26 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

It's an anti gravity feed valve, some pumps have it built in, others don't. It's not related to run on, it prevents flooding if the needle and seat weeps. Many engines used both.
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easy e
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PostPosted: Fri Jan 27, 2017 4:35 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

"... stops the flow of fuel to the carburetor when the engine is not running."
busdaddy wrote:
It's an anti gravity feed valve

I don't know if I believe in "anti gravity"... sounds like snake oil.
But, if you're selling... how much can I get a quarter oz. of anti gravity for?
I have a 'friend' that might be interested.
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PostPosted: Fri Jan 27, 2017 4:47 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

easy e wrote:
"... stops the flow of fuel to the carburetor when the engine is not running."
busdaddy wrote:
It's an anti gravity feed valve

I don't know if I believe in "anti gravity"... sounds like snake oil.
But, if you're selling... how much can I get a quarter oz. of anti gravity for?
I have a 'friend' that might be interested.

Sadly all the makers of good quality antigravity were driven out of business by the Chinese, now all you can get is the watered down knockoff stuff, and since it's from the other side of the world it works in reverse here.
I had one NOS can of the good stuff left and I poured it over my head hoping to make me look 20 again, unfortunately it must have been past it's expiry date since it had no perceptible effect Confused
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PostPosted: Fri Jan 27, 2017 8:54 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

Those VW things are called "fuel cutoff valves". They are not anti-siphon valves. They shut the flow of fuel off (gravity flow) unless
there's pressure coming from the fuel pump, i.e. unless the engine is running. Some VW engines from the early 60's had in-line F.C.V.'s,
and the VW/Pierburg "square-top" (aka pentagonal-top) had one built-in. Those pumps were used up thru 1970 models on Type I. The
71-72 Type I's again had an in-line F.C.V. (see Fig. 4-5, Fuel System chapter, in 70-79 Type I Bentley manual). The 73-74 Type I's went back to a
"non-rebuildable" fuel pump with a built-in F.C.V. (as illustrated in Fig. 4-4, i.b.i.d.). As far as I can tell, F.C.V.'s were never used in the bus
until the 72-74 Type 4 engines with mechanical fuel pumps, and that part of the pump seems to be identical with that of the old Pierburg
square-tops. [EDIT: just noticed that the same pump used on 72-74 Type I's was used on Non-US bus with 1600 engine, presumably from 72- on.]

The reason F.C.V.'s were used, is because the carb needle valve was designed as a flow control valve, not a cutoff valve. The
endless posts here on thesamba about gas filling up the crankcase where the stock cutoff valve has not been installed pretty well tells the
story. Those problems are frequently attributed to a leaky fuel pump diaphragm, but that is likely not the case 98% of the time.
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Last edited by kreemoweet on Fri Jan 27, 2017 9:49 pm; edited 1 time in total
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easy e
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PostPosted: Fri Jan 27, 2017 9:37 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

^^ most excellent reply!
So, just to clarify and summarize.... (please clarify inconsistency)
The FCV was used from whenever it was introduced.... to the end of the round top... and on ALL VW models?
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PostPosted: Fri Jan 27, 2017 10:06 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

Note Edit to my post above -

Not seeing any inconsistency ... unless you're wondering why VW put 'em on some vehicles but not on others ... I do not usually find it rewarding to
speculate on the motivations of the ancient VW organization that built these aircooled rigs.

I do not know the usage of F.C.V. except as I mentioned above. I cannot find any mention of their use in Type 2's except for those with carbed
Type 4 engine, and, as per my edit, on some later non-US late bay busses equipped with 1600 carb engines. It seems all those earlier Type 2's
had some variant of the Pierburg round-top pump (which of course has no F.C.V.), or the later "non-rebuildable" pump with no F.C.V. (as my '71 bus
was equipped with).
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easy e
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PostPosted: Fri Jan 27, 2017 10:42 pm    Post subject: Re: Fuel pump / carburetor anti-siphon valve when used? Idle cutoff Reply with quote

Hmmm... seems strange to have a Type 1 fuel pump/carb on a Type 2 (which is the case).... and use the FCV only on Type 1.

Absent of further input...
I'll try to look for some survivor Typ 2 40hp - early 1500 pics of fuel pumps.
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PostPosted: Sat Jan 28, 2017 11:05 am    Post subject: Re: Fuel pump / carburetor fuel cutoff cut off valve when used? Reply with quote

You can add type 3's into the mix as well.

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PostPosted: Sat Jan 28, 2017 6:13 pm    Post subject: Re: Fuel pump / carburetor fuel cutoff cut off valve when used? Reply with quote

Adding to what is already posted:
For Bugs and Type 3s the cutoff valves are 1965 only because in 1966 VW changed to the fuel pump with the 4 screws on top, which had this shut-off built into the pump.

I am not sure why Buses didn't use it or why they used the screw-in pump so much later.
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