Crankcase full of gas, carb question

windfish

'70 bug, '71 1600cc DP Engine, Carter electric fuel pump (pressure tested, right at 3psi at the engine).

It drove fine Monday and Tuesday, so I stopped and got her a full tank on my way home Tuesday. Wednesday morning (well, today) she goes thud when I turned the key, so I checked it and the crankcase was full of gas (again).

From what searching I've done this can be caused by a bad needle valve letting gas in.
Unfortunately I park on a hill, so unless I start backing in (which I can do) the tank is going to be higher than the carb inlet.

What I'm not clear on is that the float seemed to be at a good level when I popped the top off the carb -

Image may have been reduced in size. Click image to view fullscreen.

I kind of thought that if the needle valve was sticking the carb would be full to the top with gas?
Anything else I should replace?

Wolfgangdieter · Posted: Wed Oct 08, 2014 4:38 pm Post subject:

think you nailed it - hill and needle valve. Might add as lawn mower gas cut off valve - good anti-theft device too.
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busdaddy · Posted: Wed Oct 08, 2014 4:39 pm Post subject:

Manually fill the float bowl and see if the tide goes out by itself.
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jlex · Posted: Wed Oct 08, 2014 5:50 pm Post subject:

I hope you change that oil out before you burn out your bearings due to the gas dilution of the oil.
Sounds like a severe problem....
Maybe an electric shutoff valve will solve your problem:
http://www.dan-marc.com/rv-parts-12-volt-fuel-shut-off-valves.html
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windfish · Posted: Wed Oct 08, 2014 6:05 pm Post subject:

Sure.
Gas and oil didn't even get to mix any, pulled the plug and got clean oil followed by a cascade of gas.

Took the needle valve from my old carb, ran some carb cleaner through it, and put it on. Clean oil, she started right up. I'll drive her over to the gas station (~2 miles), fill her up, and I'll know by morning if she's fixed.

Thanks guys.

johnnypan · Posted: Wed Oct 08, 2014 6:16 pm Post subject:

Parking on a hill wont develop enough pressure to open your float valve..a bad float or a bad needle and seat is causing your issue,not where you park,or if the engine is running or not..

jlex · Posted: Wed Oct 08, 2014 6:29 pm Post subject:

Johnnypan's giving good advice on a potential float issue. As long as you're playing around, take the float out and put it in warm water. It'll cause the inside air to expand and will form bubbles if the float is bad.
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busdaddy · Posted: Wed Oct 08, 2014 6:50 pm Post subject:

That bowl sure looks low, I wonder if the carb has a misdrilled/overdrilled passage that allows the bowl to drain down the throat, wouldn't be the first time a Chinese or Brazilian carb didn't quite meet the standards (if that is one).
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windfish · Posted: Wed Oct 08, 2014 7:03 pm Post subject:

Heh, it's a rebuilt German Solex 34PICT-3, done early this year by Tim at volkzbitz.
Worst comes to worst I'll send it back, at this point I'm nearly positive it's something in the carb at fault. But I'd lose my bug for a few weeks and the weather is still halfway decent, so if I can fix it I'd rather start there.

Float seems to be fine; I took it out and held it up to the light, no sign of any liquid in 'er.

Just got back from the gas station, I'll have my answer by morning (assuming the needle valve from my old carb isn't screwed up as well).
If clean oil, fix'd. If full of gas again something is still amiss.

Edit - just a note, it started doing this after sitting for a month while I worked on other parts of the car. Prior to that she ran great.

HRVW · Posted: Wed Oct 08, 2014 7:19 pm Post subject:

A tank will hold about 10 gals of gas and I would NEVER fill it unless driving a long distance on the fwy.

A good habit would to just buy gas at the 1/4 mark up to the 3/4 maybe 5-6 gals approx. (Today maybe a $20 bill) Too many gas stations with the same price on the pump to have a FULL tank...would have saved a little headache here.

busdaddy · Posted: Wed Oct 08, 2014 7:29 pm Post subject:

kreemoweet · Posted: Wed Oct 08, 2014 8:06 pm Post subject:

It's really a shame that none of you guys that think a carb float/needle valve can prevent the OP's problem was around to clue
in the VW engineers back in the day. Those poor saps seem to have had the notion that a fuel cutoff valve was necessary "... to
prevent the gradual flow of fuel to the carburetor when the engine is not running", and wasted a bunch of money putting them in these cars.
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Juanito84 · Posted: Wed Oct 08, 2014 9:25 pm Post subject:

This is a problem I mentioned earlier in this thread.

http://www.thesamba.com/vw/forum/viewtopic.php?t=606078&highlight=
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busdaddy · Posted: Wed Oct 08, 2014 10:04 pm Post subject:

windfish · Posted: Thu Oct 09, 2014 8:44 am Post subject:

Well, that appears to be it.
Checked the oil this morning and it was the same level I left it at last night. Full tank of gas, nothing leaking into the crankcase. Joy.

Will keep a close eye on it for another week or so just to be sure, have to change the oil again soon anyways. Seems like it takes a good three changes to get most of the gas smell out, one drop infects the whole sump.

btw, the electric pump is pushing 3psi at the engine according to my mechanic's gauge. And that wasn't really the problem here, as it dumped two gallons into my crankcase overnight -- unless you think the electric pump pushing 3psi damaged the needle valve somehow.
But again, this only happened after the car sat for a month, so... /shrug.
Probably will go ahead and get a pressure reg to bring it down to 2psi anyways, this one looks decent.

I've never heard not to fill up the tank? Not topping it off (and thus filling the filler tube), sure, but till it clicks once should be fine? My entire fuel delivery system is new (tank, lines, hose, filler tube, pump, filter), the idea that VW would design a gas tank that couldn't tolerate being filled up seems a little odd to me.

The 34PICT-3 actually has an electric cutoff valve built in, but I was thinking that it was being bypassed by the misbehaving needle valve overfilling the carb... however, given the level in the float tank dropped down a bit, might be worth testing.

I'll keep an eye on her
Thanks guys.

Juanito84 · Posted: Thu Oct 09, 2014 2:11 pm Post subject:

I don't think 3psi damaged the needle valve. I wouldn't suspect the needle valve unless you start getting flooded while driving around. I just wouldn't trust the needle valve to keep gasoline from syphonning into the engine on a hill. VW didn't trust it either.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

jlex · Posted: Fri Oct 10, 2014 4:57 am Post subject:

johnnypan · Posted: Fri Oct 10, 2014 5:27 am Post subject:

JasonBaker · Posted: Fri Oct 10, 2014 11:27 am Post subject:

Have you taken the float out and checked to see if it has gas inside?

Maybe I missed it, was it was ruled out? My bet is still on the float.

lobsterlike · Posted: Sat Oct 11, 2014 12:33 pm Post subject:

The only way to know is to check. Test the needle and seat by blowing air through the fuel inlet while pushing gently on the needle part of the needle/seat. Remember that the needle and seat has a rubber (probably Viton) seal and any amount of ethanol will degrade it over time. Keep in mind that dirt in the fuel system or pieces of rubber from the inside of your hoses will get stuck in the needle and seat and prevent it from closing. I carry a spare needle and seat in the glovebox for this reason.


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