help needed, carb problem

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Dec 17, 2005 | 06:48 PM

LS1BirdDRG

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From: Alvin, TX

help needed, carb problem

Installed a Holley 130gph mechanical fuel pump with adjustable regulator. I have a 4150 style 700dbl pmpr. Adjusted down to 6 psi but the fuel is just dumping like crazy. Adjusted the floats and pulled both needle and seats to see if they had trash. What can be done to fix this? Problem is primary and secondaries. Had no problems before pump install. I'm at a loss, what am I missing here?

Dec 18, 2005 | 10:45 PM

LS1SSII

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From: Peoria, IL

Where is the gas coming from? Vent tubes? Squirters?

Dec 21, 2005 | 02:27 AM

78TA

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From: zanesville, ohio

I would back the pressure down to about 5psi and try that, if it still does it, keep backing it down until it quits holding the needles open. I have had this problem before on a s-10 I put a carbed sbc in and used the factory electric fuel pump and a regulator before the carb. The s-10 was doing the same thing you are talking about and i had to turn fuel pressure down to 4.5psi to get it to quit.

Dec 21, 2005 | 06:10 PM

LS1SSII

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From: Peoria, IL

That is not a good fix. There is obviously a carb problem that needs to be addressed. If you back down the pressure to much you can cause a lean condition and wind up breaking parts. If you did not rebuild the carb I would suggest you do that first. Also, check the floats to see if they are still good.

Dec 22, 2005 | 03:09 AM

LS1BirdDRG

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From: Alvin, TX

The gas was coming from the vent tubes.
I swapped out both n/s and the power valve and it's driveable now. It's still not 100% right but getting closer. Seems I have to turn the n/s adj nut all the way down practically.

Sometimes when the secondaries kick in it backfires through the carb. I know the timings good. Is that from lack of fuel in secondaries or too much?
Sorry I didn't reply right away, been busy. Thanks for the help guys!

Dec 23, 2005 | 06:17 PM

78TA

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From: zanesville, ohio

Quote:

Had no problems before pump install.

This would lead me to believe it is a pressure problem.

There is only a couple things i can think of that would cause fuel to come out of vent tubes and they are: floats adjusted too high, something stuck in the needle and seats holding them open, too high fuel pressure causing needle and seats to stay open, leaking/bad floats that sink and hold needle open, and fuel boiling in the bowls.

you said you adjusted floats, where did you set them at? level with the bottom of the sight plugs is where it should be. Is this an intermitent problem or is it all the time?

I am no carb expert, but i have played with them a bit.

Hope this helps.

Dec 26, 2005 | 06:11 AM

LS1BirdDRG

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From: Alvin, TX

My fuel bowl problem is fixed. I'm not 100% sure what the issue was, but between some possible trash or faulty n/s it's good. Got both levels right at the bottom of the sights. Thanks for all the help. Now, on to other little gremlins!
Oh yea, I changed the acc pump cam and no more backfiring.