Serious problem: fuel shoots out of the vent tube on the carb. - Chevelle Tech

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post #1 of 6 (permalink) Old Apr 2nd, 07, 12:46 PM Thread Starter
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Dave
 
Join Date: Mar 2004
Location: Goldsboro, NC
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Serious problem: fuel shoots out of the vent tube on the carb.

I got a serious problem and am not sure where to start.

Today I went to go fire up the Chevelle to pull it out of the garage and snap some pics of it. It fired up right away (after not being ran for a good week to two weeks) but quickly died.

Went to restart it, this time it doesn't want to fire....it tried a few times but didn't. Then I heard fluid running all over the floor so i stopped cranking.

Popped the hood and discovered the intake manifold has gas puddled all over it. Didn't know where it was coming from so I wiped it all up and then asked my wife to come crank the engine to see what was up.

She starts cranking and the engine gets a few rpms, then gas starts shooting out of the front vent tube on my 750 Holley. This is a part number 0-82750 carb.

Now up to today this carb has never done this, I'm wondering if this is what happens when the float sticks on a Holley?

I do have a Summit inline fuel filter as well as the filters that came with the carb. Is it still possible to get crap in the carb even with two filters?

Another thing I'm wondering....I just also recently replaced the mechanical fuel pump (Carter 120 gph 6.5 PSI) with a Holley mech. pump that is a 130 gph and the PSI is set at 9.....I did run the engine like this for a day until I was able to get myself a fuel pressure regulator, then I set the pressure for 7 1/2 PSI and haven't had any problems with it. Is it possible that short brief period of 9 PSI damaged something inside the carb?

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #2 of 6 (permalink) Old Apr 2nd, 07, 12:58 PM
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Keith
 
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Re: Serious problem: fuel shoots out of the vent tube on the carb.

If it was working fine before, then you probably have dirt in the needle and seat assembly. Remove the assembly, blow it out and re-install. You are running at the limit on fuel pressure and that can cause problems too.
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post #3 of 6 (permalink) Old Apr 2nd, 07, 1:01 PM
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Mike
 
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Re: Serious problem: fuel shoots out of the vent tube on the carb.

You have some debris in the needle and seat. It has happened to me a couple times on my Camaro and I have a couple of filters inline also.

I ended up taking the needle and seat apart, blowing it out and when I put it back together, no fuel coming from the vent.

Mike
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post #4 of 6 (permalink) Old Apr 2nd, 07, 1:03 PM
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Mike
 
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Re: Serious problem: fuel shoots out of the vent tube on the carb.

Beat me too it Keith.
Great minds think alike.

Mike
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post #5 of 6 (permalink) Old Apr 2nd, 07, 1:09 PM
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norval
 
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Re: Serious problem: fuel shoots out of the vent tube on the carb.

I agree with the dirt in the needle. Using a 5/8th wrench you can loosen the nut on the needle and screw it out the top. Plow it out and reinstall. You do not need to take the carb apart. You will have to start the motor to reset the float level and you want it just barely trickling out the front float bowl.
Also to start with try and get it about the same height as when you took it out to get close.
You can remove the screw from the top and look at the height.
Also I feel the pressure is too high. Set it around 6 psi.
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post #6 of 6 (permalink) Old Apr 2nd, 07, 3:02 PM Thread Starter
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Dave
 
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Re: Serious problem: fuel shoots out of the vent tube on the carb.

Thank you I will definitely do this, though I also need to replace the 4.5 power valve with a 3.5 as the vacuum signal in idle is very low (6 hg due to the 240/246 duration cam) so I'll probably just remove the bowl.

The instructions recommend 5-7 PSI, I may bump it down half a PSI. Funny thing is the fuel pressure gauge reads up and down differently for some reason....

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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