Stalling when accelerating
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New User
Joined: Apr 2005
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Stalling when accelerating
I'm the new owner of a 1976 F250 with a 460 and a motorcraft 4 barrel carburetor. I've changed the plugs, wires, rotor, air filter and a few other minor things. The main engine trouble I'm having is this, the engine stalls, it doesn't die, when I accelerate quickly. Slow steady acceloration happens without problems, but as soon as I stomp the pedal, she stalls.
I've sprayed some carb cleaner in the top and ran some cleaner through the gas tank. I'm hoping that my carb just needs to be adjusted. I've also tried adjusting what I beleive is an accelorator pump adjustment, but it hasn't helped.
What next? Any other threads I can read?
thanks
I've sprayed some carb cleaner in the top and ran some cleaner through the gas tank. I'm hoping that my carb just needs to be adjusted. I've also tried adjusting what I beleive is an accelorator pump adjustment, but it hasn't helped.
What next? Any other threads I can read?
thanks
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Sounds like either the accelerator pump in the carb is bad or the secondaries are opening too fast. Does it have the spreadbore carb with the small front barrels and really large rear ones? If so, these carbs has a vacuum diaphram that holds the secondary air flap to keep it from flopping open and causing a lean bog. It could be bad.
Also check to make sure that the vacuum advance is working properly on the distributor.
Also check to make sure that the vacuum advance is working properly on the distributor.
Senior User
Joined: Dec 2002
Posts: 177
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From: Escondido Ca.
I agree with lxman1, sounds like an accelerator pump going out. If you can accelerate slowly then i would guess that most likely the pump is bad. Extremly cheap and easy fix, even if it isnt bad, it doesnt hurt to replace it...
Infidel
Joined: Aug 2003
Posts: 1,115
Likes: 2
From: Elkhorn WI
Originally Posted by LxMan1
Sounds like either the accelerator pump in the carb is bad or the secondaries are opening too fast. Does it have the spreadbore carb with the small front barrels and really large rear ones? If so, these carbs has a vacuum diaphram that holds the secondary air flap to keep it from flopping open and causing a lean bog. It could be bad.
Also check to make sure that the vacuum advance is working properly on the distributor.
Also check to make sure that the vacuum advance is working properly on the distributor.
Ive got the same problem but mine is a 2bbl 360 FE. How do you check to see if the vacuum advance is working on the distributor? The accelerator pump is brand new.
Senior User
Joined: Dec 2002
Posts: 177
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From: Escondido Ca.
I think to check if the advance is working, first check if theres vacuum at the line. Then, when you unplug it from the distributor, your engine idle should change cause the timing is changing. If you got a timing light, hook it up and look at what your timing is with the advance pluged in, and then unplug the line and the timing will change. I know that it will change if the advance is working. Anyone feel free to correct me if im wrong though 
Postmaster
Joined: Feb 2003
Posts: 4,043
Likes: 4
That works if you have manifold vacuum at the distributor advance. If you have ported vacuum then the idle won't change. If it is ported vacuum (there is no vacuum in the line at idle) you could simply tap into a maifold vacuum source temporarily to test it. When you plug the vacuum into the distributor, the engine idle speed should increase.
Posting Guru
Joined: Sep 2003
Posts: 1,192
Likes: 1
From: lino lakes, mn
you can also pull the dist. cap and either suck on the vacum hose or use a vacum pump on it and watch the base plate in the dist. it dhould move when vacum is applied and you should feel resistance if you are sucking on it
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Logistics Pro
Joined: May 2004
Posts: 4,998
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From: Maryville
The power valve in the carb will also cause this condition, if it has back fired through the carb, it blows the power valve. Check to see if the accelerator pump is leaking, it's mounted either on the front or under the carb, if it leaks, it's bad, if it's old, I'd replace it for safety sake, leaking fuel on a hot engine is a fire waiting to happen.
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Fleet Mechanic
Joined: Feb 2005
Posts: 1,782
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From: Lower Mainland B.C.
Sounds like a plugged fuel filter, just enough flow to accelerate slowly but not enough flow to accelerate quickly.
This happened to me 2 months ago, I changed the fuel filter at front of carb, no pmore problems.
Check the simple things first before ripping your carb apart or buying parts you don't need.
This happened to me 2 months ago, I changed the fuel filter at front of carb, no pmore problems.
Check the simple things first before ripping your carb apart or buying parts you don't need.
