Strange Acceleration
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Elder User
Joined: Jul 2004
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From: Westminster, Colorado
Strange Acceleration
I've been having an interesting thing happen in the ol' truck.....1967 F-250 4x4 390/4bbl Edelbrock 1406.....When really "giving it the gas" to tear away from a stop light of pass another car, I'm noticing a "flat spot" slightly after I stop "gassing it"....the engine has the power to pass the car, but then runs sorta flat, like the gas running out......then resumes after a second of two....Could I be depleting the gas from the carb faster than my new Electric fuel pump can refill it? Or do I have dirt somewhere? (how with 3 filters?)
Lead Driver
Joined: Jan 2003
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From: Ohio
So, you are actually "lifting" slightly and it seems to lay down?
I'd say it's closing the secondaries..and then as you press into it again it takes a moment for them to reopen again(since you remove the vacuum signal by closing throttle slightly).
That's one scenario. I would bet it's NOT running out of fuel. Can't even imagine you're using that much fuel...not even close to max'ing the pump.
I'd say it's closing the secondaries..and then as you press into it again it takes a moment for them to reopen again(since you remove the vacuum signal by closing throttle slightly).
That's one scenario. I would bet it's NOT running out of fuel. Can't even imagine you're using that much fuel...not even close to max'ing the pump.
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From: Westminster, Colorado
Yeah....It happens a feww second after I get back into regular throttle...I give it the "big gas" when the light turns green and get through my turn, shift and then accel normally and that's when it happens.....like you're running on half the engine so to speak....you can tell there is gas, but not enough....like it's ready to dive into a stall, but if I keep giving it the gas and maybe pump it a little it stays running ans straightens out.....feels like momentary dirt clogs......but I have 2 new filters (one on elec fuel pump one in line before carb)....
I was wondering if the electric fuel pump simply couldn't pump the "extra gas" that the mechanical one did under rev......but that can't be it.
I was wondering if the electric fuel pump simply couldn't pump the "extra gas" that the mechanical one did under rev......but that can't be it.
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Joined: Mar 2004
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From: SOUTH CAROLINA
you could have a weak spring in the accelerator pump also. some carbs (im assuming you have a four barrel) have a variety of springs that come with the carb. when you put the gas to it and use whats in the accelerator housing the spring may not be pushing out as it should so its not drawing fuel back into itself fast enough giving you a flat spot in the throttle. just a thought. good luck.
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Elder User
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From: Westminster, Colorado
This carb is practically brand new....I bought it and installed it in February. Could this "spring" you speak of be too weak from the factory? Keep in mind, I never had this problem before I added the electric fuel pump....
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From: Westminster, Colorado
Well....the truck started doing this little thing while driving......sorta getting a jitter every now and then....I started thinking dirt in the carb.....then when I stopped at a light, I heard a whistling sound.....looked under the hood and the PCV valve had come out of the Valve cover....I don't know if this is the problem, but I'll keep driving and see.
As for the heat......I bought a new starter and a heat blanket for it....but have not yet installed it.....I'm still doing the "lift the hood and remover the top of the air cleaner thing" every time I stop if it's over 80 degrees outside. The starter did seem weak and I figured I'd replace it right this time to eliminate that as a potential source of the problem.
As for the heat......I bought a new starter and a heat blanket for it....but have not yet installed it.....I'm still doing the "lift the hood and remover the top of the air cleaner thing" every time I stop if it's over 80 degrees outside. The starter did seem weak and I figured I'd replace it right this time to eliminate that as a potential source of the problem.
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Elder User
Joined: Jan 2002
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From: Mansfield, Texas
what ever you find as the source of the problem.... do all of us a favor and reply in the original post the fix for that problem. It will help for future readers to solve their problems.
I realize you haven't found it yet, but keep us up to date when you do. Or even what you have tried. (on the original post).
Good luck with both.
Robert P.
I realize you haven't found it yet, but keep us up to date when you do. Or even what you have tried. (on the original post).
Good luck with both.
Robert P.
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Elder User
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From: Westminster, Colorado
I have a new fuel pump.....just put a new electric one in.....and changed the fuel filter and chacked the carb bowls for dirt.....still getting the slight jitter every now and then.....I think I may need to clean out the tank.....as I have never done that...Perhaps the strainer is getting blocked in there?