Starts (and runs) only when gas poured in carburetor

[manxome]

I'm trying to figure out a cold start problem on my 1966 Type3 (Dual Carburetors).

The car will crank just fine and will do so for quite a while before getting tired. While it sometimes would start if I pumped the gas or held the gas pedal to the floor, it now won't catch anymore.

If it has been sitting, it sounds as if it will just about catch and I will hold the pedal to the floor - but it gives up and just keeps cranking.

If I put about a tablespoon of gas in each carburetor, the car will crank a bit, then catch and start up. After this point, it runs OK - doesn't immediately stall and I can leave it idle as long as I'd like.

Given what I've observed, I'm feeling the spark and air are OK, the fuel line is not clogged, nor are the jets.

I'm not entirely sure where this leaves me. It seems to me if the fuel pump were under pressure, or if the jets were partially clogged, I'd have problems after it started, such as stalling out.

Any thoughts? I'm not sure where to focus my troubleshooting and attention just now...

Thanks!

[Tram]

With the engine cold and the chokes open/ air cleaner removed, activate the linkage and see if you observe any fuel squirting down into the carburetors when you do this. If you don't, remove the carb tops. Do you have gas?

I'm thinking one or both accelerator pumps are shot or a passage is plugged. If it hesitates on acceleration once it's running that's your second clue for bad accel pumps.
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[KTPhil]

Didn't some of the dual carb cars require the anti-siphon valve? Maybe that's bad or missing, and it is running dry when it sits. Then once started it burps the air out and runs ok.

(upper left in photo below):

Hard to see, I know. Maybe kinda like this one?:

Check out this thread about the Bug anti-siphon valve:
http://www.thesamba.com/vw/forum/viewtopic.php?t=568271

[andrewvwclassic]

[ataraxia]

[manxome]

Thanks!

Will update when I have some results...

[manxome]

So I've determined the following:

- When the engine is cold and I hold open the air valve and shine a light down each carb and then actuate the accelerator linkage, I do NOT see any gas squirting in. I do hear puffs though.

- At each carb, when I disconnect the fuel line to the carb and collect the fuel, I get about a tablespoon+ of fuel glugging out at what looks to be a good force in about 3 rotations (let's say about 1/2 Tablespoon of fuel per pump).

I'm taking a look at how to clean the jets.


Some other responses to the replies:

- I have to get it started and on the road to know if I'm having pauses when accelerating. I want to say that when I did have it on the road last year, it paused when cold, but that went away when it was up to temperature.

- I do NOT have an anti-siphon valve. From the fuel pump, it goes right into a clear housing showing the filter. (When the engine is cranking, it looks as if fuel is passing through this by the way...)



Please feel free to comment further. I certainly don't mind if someone calls me out on a bad assumption -- I'm new to this engine and era!

[Tram]

[sima112]

Hi Manxome,

Could you write me what was your problem, please? I have exactly the same symptoms and would help me a lot to narrow down my searching.

Many Thanks Sima