backfiring in carb?
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New User
Joined: May 2007
Posts: 10
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backfiring in carb?
i have a 1979 ford f-250
its got a 351w in it
its been sitting 4 about 3 years doing nothing and i just inharited it form my dad. he dident want it any more
i cleaned the carb up and it dident iddl but could rev up
now it iddles but dosent rev up with out it dieing and some times a back fire comes out of the carb with about a 4 inch flame
also when it runs it sounds like air is leaking out, its a soft hissing sound kind of
it also dies or trys to when u try to rev it up by pushing the peddl in slowly
if u pump it it will rev up but then the flame will come
also i need a diagram of the vacume sysytem because my dad monkied around and took off the system
now the vacume advance isnt hooked up.
but it ran good with out it before
im confused so i need your guys brain power
thanx
Dave
its got a 351w in it
its been sitting 4 about 3 years doing nothing and i just inharited it form my dad. he dident want it any more
i cleaned the carb up and it dident iddl but could rev up
now it iddles but dosent rev up with out it dieing and some times a back fire comes out of the carb with about a 4 inch flame
also when it runs it sounds like air is leaking out, its a soft hissing sound kind of
it also dies or trys to when u try to rev it up by pushing the peddl in slowly
if u pump it it will rev up but then the flame will come
also i need a diagram of the vacume sysytem because my dad monkied around and took off the system
now the vacume advance isnt hooked up.
but it ran good with out it before
im confused so i need your guys brain power
thanx
Dave
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
The problem is most likely an accelerator pump not working or retarded timing.
Start by shutting off the engine and removing the air filter. With a light, look down in the primary bores of the throttle plate and snap the throttle open while watching for streams of gas. If there are no streams of fuel when you snap the throttle open, then the accelerator pump is not working.
If there ARE streams of fuel, then set the initial timing. If the initial timing is okay, then see if you can slowly increase RPM while watching the timing mark with the light to see if it advances with speed. If it does, then the centrifugal advance is working.
By the time you get through all that, you should have found the problem.
Good luck,
Start by shutting off the engine and removing the air filter. With a light, look down in the primary bores of the throttle plate and snap the throttle open while watching for streams of gas. If there are no streams of fuel when you snap the throttle open, then the accelerator pump is not working.
If there ARE streams of fuel, then set the initial timing. If the initial timing is okay, then see if you can slowly increase RPM while watching the timing mark with the light to see if it advances with speed. If it does, then the centrifugal advance is working.
By the time you get through all that, you should have found the problem.
Good luck,
Elder User
Joined: May 2007
Posts: 514
Likes: 0
From: Northern Colorado
Also if you're hearing a loud hissing that you don't think is coming from the carb itself, look for vacuum leaks. Check any of the remaining lines carefully for cracking, but also inspect the back of the carb, base plate and manifold area for ports that should have lines or plugs - if you find plugs, at the very least look at them for integrity, or replace them with the appropriate vacuum line.
