Carb Problems, Help Please :]
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From: Phoenix
Carb Problems, Help Please :]
my truck is a 1976 Ford f100 engine swapped to a 1978 351m with a motorcraft 2150 2 barrel carburetor.
i just finished cleaning it, rebuilding it, and adjusting it to specification (the dry float level, the pump stroke, choke valve pulldown, fast idle cam linkage, automatic choke, choke unloader, and slow idle).
when i step on the gas, the engine acts like it dies for less than a second, and then acts normal. when the engine is cold its even worse; sometimes it shuts off! but its only in a certain area of the pedal that it does it which is just at the beginning... after that it runs very smooth! help please?
i just finished cleaning it, rebuilding it, and adjusting it to specification (the dry float level, the pump stroke, choke valve pulldown, fast idle cam linkage, automatic choke, choke unloader, and slow idle).
when i step on the gas, the engine acts like it dies for less than a second, and then acts normal. when the engine is cold its even worse; sometimes it shuts off! but its only in a certain area of the pedal that it does it which is just at the beginning... after that it runs very smooth! help please?
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From: Phoenix
gas does not shoot down the boosters :[
Laughing Gas
Joined: May 2006
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From: Port Orchard Wa
check to make sure you have the linkage on the front installed correctly. Throttle should activate the pump lever on the front. If that is ok, I would remove the pump lever/cover assembly from the front of the carb and make sure the diaphram is installed correctly/ not torn. There should also be a little rubber check valve in the front of the carb under the cover and diaphram.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I'm sure you have figured out that this is not desired behavior 
For whatever reason, the accelerator pump is not actuating. This causes a lean condition during a sudden change in throttle position because fuel is heavier than air per unit volume. This goes away after a brief moment once the fuel catches up.
The following pieces are necessary for the accelerator pump to function, many of which are described above:
* Linkage on the outside
* Pump diaphragm
* Pump spring (under the diaphragm)
* Umbrella check valve (under the spring)
* Check ball (inside the throttle body)
* Check weight (inside the throttle body)
Missing any of these pieces will cause the behavior you describe. Go through and check your work again.
For whatever reason, the accelerator pump is not actuating. This causes a lean condition during a sudden change in throttle position because fuel is heavier than air per unit volume. This goes away after a brief moment once the fuel catches up.
The following pieces are necessary for the accelerator pump to function, many of which are described above:
* Linkage on the outside
* Pump diaphragm
* Pump spring (under the diaphragm)
* Umbrella check valve (under the spring)
* Check ball (inside the throttle body)
* Check weight (inside the throttle body)
Missing any of these pieces will cause the behavior you describe. Go through and check your work again.
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New User
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From: Phoenix
turns out the umbrella check valve was torn... i am going to try to look for it by itself online since i dont want to pay another 30 dollars just for that piece! thanks guys 
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Ford Parts Specialist
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From: Simi Valley, CA
C4AZ-9576-A .. Accelerator Pump Check Valve (Motorcraft CM-825).
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I would be curious to know if you find it, as I've never seen it sold individually at a parts store (the only time it gets replaced is during a carburetor rebuild). I do see Holley ones on Summit that look the same, no idea if they are the same size: Search Results for umbrella check valve - SummitRacing.com
The next time you install it, be sure to lubricate the "shaft" with WD-40 so that it pulls through more easily.
The next time you install it, be sure to lubricate the "shaft" with WD-40 so that it pulls through more easily.
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New User
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From: Phoenix
im looking on the orielly and napa websites for the check valve and cant seem to find it... what stores sell them? ford dealership?
Postmaster
Joined: Aug 2005
Posts: 2,760
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From: Gadsden Purchase
Mike's Carburetor Parts
Carburetor Kits & Parts | High Quality
$1.95 each. :)
Thanks for the numbers and the idea to look for the parts separately, Bill. :)
Alvin in AZ
ps- Three of each of these...
a) pump diaphragm
b) umbrella valve
c) power valve
...should do me for a lifetime since they are the only things I've found that
actually wear out. I soak the new gaskets in silicone spray and/or silicone
grease. Hmm... anti-seize would work too I betcha. ;)
pps- http://www.panix.com/~alvinj/file12/choke1.jpg
dohn need no steen keen choke
Carburetor Kits & Parts | High Quality
$1.95 each. :)
Thanks for the numbers and the idea to look for the parts separately, Bill. :)
Alvin in AZ
ps- Three of each of these...
a) pump diaphragm
b) umbrella valve
c) power valve
...should do me for a lifetime since they are the only things I've found that
actually wear out. I soak the new gaskets in silicone spray and/or silicone
grease. Hmm... anti-seize would work too I betcha. ;)
pps- http://www.panix.com/~alvinj/file12/choke1.jpg
dohn need no steen keen choke
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New User
Joined: Oct 2012
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From: Phoenix
Mike's Carburetor Parts
Carburetor Kits & Parts | High Quality
$1.95 each.
Thanks for the numbers and the idea to look for the parts separately, Bill.
Alvin in AZ
Carburetor Kits & Parts | High Quality
$1.95 each.
Thanks for the numbers and the idea to look for the parts separately, Bill.
Alvin in AZ
DON SANDERSON FORD in Glendale AZ has 16 = 623-842-8643.
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New User
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From: Phoenix
thanks NumberDummy :] ill drop by and get it monday!
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