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Old 08-15-2008, 06:59 AM
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Could This Be A Fuel Pump Issue?

My car has a 350 Chevy engine with an Edelbrock 1406 Performer (600 cfm.) carb. and a mechanical fuel pump. The car starts and runs fine with the exception of after it's sat for 6 hours or more. About 5 minutes after a cold start the car acts as if it's running out of gas. If it's idling, it may die. If I'm driving it, it will cough and sputter like I'm running out of gas. I have to put it into neutral and keep stepping on the gas to keep it running. This starts about 5 minutes after a cold start and will continue for anywhere from 10 to 15 minutes. I thought I had a carburetor/choke problem, but everything is set properly and that doesn't appear to be the problem. Could this be a fuel delivery issue? Is there a possibility I'm using up the fuel in the in the carburetor bowl and fuel pump and then having problems until the fuel is replenished in the fuel line between the gas tank and the carburetor?

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Old 08-15-2008, 07:30 AM
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not sure

the only way to tell is to watch your fuel with a pressure gauge or in a clear filter my money is on carb issues edlebrock carbs are known for baffeling fuel issues
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Old 08-15-2008, 01:02 PM
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Quote:
Originally Posted by 10mikeymike
My car has a 350 Chevy engine with an Edelbrock 1406 Performer (600 cfm.) carb. and a mechanical fuel pump. The car starts and runs fine with the exception of after it's sat for 6 hours or more. About 5 minutes after a cold start the car acts as if it's running out of gas. If it's idling, it may die. If I'm driving it, it will cough and sputter like I'm running out of gas. I have to put it into neutral and keep stepping on the gas to keep it running. This starts about 5 minutes after a cold start and will continue for anywhere from 10 to 15 minutes. I thought I had a carburetor/choke problem, but everything is set properly and that doesn't appear to be the problem. Could this be a fuel delivery issue? Is there a possibility I'm using up the fuel in the in the carburetor bowl and fuel pump and then having problems until the fuel is replenished in the fuel line between the gas tank and the carburetor?
Yes it could be.

Bogie
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Old 08-16-2008, 07:12 AM
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crack the gas cap open just a bit to know for sure it's not a lack of venting causing a vacuum in the tank....

mount a $5? clear plastic Purolator filter on the tank line at the pump inlet to know that it's not a fuel pick up issue...

test your fuel pump pressure, 3.0psi minumum, 5.5psi max allowed for the Edelbrock....
if the floats needles and pump check valve are sealing it will hold the pressure for roughly 15minutes after you turn off the motor.....

the carb has a independent idle circuit, the 2 tiny brass tubes next to the rods caps are the idle air bleeds....
with air or spray carb cleaner give them a squirt to be sure they are open.....

my $.02:
on the Edie, if it has been working fine and starts acting "whacko" for no apparent reason it is very very likely because dirt got into one or more of the many fuel channels...
the re-build gasket kit is about $10 and it's not rocket science at all to tear it all the way down, clean all, re-assemble....

your syptom can be a sticking centrifugal advance plate

does it work ok after the 5 minute epileptic episode when the motor gets to full temp?
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Old 08-16-2008, 03:54 PM
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The car has a fuel regulator on it. I thought these were primarily for use with electric fuel pumps. Aren't mechanical fuel pumps pretty much consistent? I think I'll bypass the regulator and see if that makes a difference. Even though I haven't done anything to determine the cause yet, I have difficulty believing it's the carburetor since the car starts and runs fine once it's past the initial start after sitting for an extended period.
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Old 08-17-2008, 08:13 AM
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I agree,
that's why I wrote my post starting at the very beginning of supply line and mentioned the carb last....

(all that a mech pump is,,, is the rubber diaphram pushes gas past a check valve with a specific psi rated bypass spring so it will build only so much psi)

different mech pump models do have different springs for different psi....
many carbs do want 7psi which will flood a Edelbrock....

when you do the pump psi test:
check the psi with the motor and pump cold, compare to the psi when the pump and motor are at full temp (a pump close to the end of it's life will show up to 2psi less hot due to a weakened spring and/or worn check valve bore)
also keep a watch for air bubbles in the clear filter after you turn off the motor (indicating the check valve may have dirt in it allowing it to leak)

(small chance but only takes 2 minutes) loosen the rods caps screws and rotate to free the rods, remove and clean and spray the vac plungers and springs with WD40....
(your symptom can be the rods sticking in the up (rich) position as the motor warms up)...
CAUTION: the caps screws are soft,,,retighten gently to just past snug,,,or you will twist the heads off...

while you've got the WD40 out do spray the crap out of the dist cent advance assembly...

it does sound like "something" is hanging up as it warms???

Last edited by red65mustang; 08-17-2008 at 08:45 AM.
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Old 08-17-2008, 12:13 PM
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carburetor icing
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