1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck
Sponsored by:
Sponsored by: Moser

carb poops out? why i ask. 300 6 cyl.

  #1  
Old 03-07-2011, 08:59 PM
79str8six's Avatar
79str8six
79str8six is offline
Junior User
Thread Starter
Join Date: Mar 2011
Posts: 66
Likes: 0
Received 0 Likes on 0 Posts
carb poops out? why i ask. 300 6 cyl.

i have a 1979 ford f250..
just figured out charging issue thanks to FMC400.

anyway....here goes...

my truck will idle fine or even drive(if your light..super light on gas pedal)..but when you give it gas fast i will stall out..makes for very diffuclt start being i have a manual 4 speed,it does have a manual choke...the only way i found works better is to have choke half open all the time. This cant be right..it still will wanna bog/stall with choke at half its just a whole lot better than with choke off.

recent carb kit thrown in it (carter 1barrel)....stil does it.
could or is there an adjustment on carb that may be out of wack??
300 cyl.

need advice
 
  #2  
Old 03-07-2011, 09:43 PM
wyckedcombo17's Avatar
wyckedcombo17
wyckedcombo17 is offline
Posting Guru
Join Date: Sep 2009
Location: Suburbs of Chicago
Posts: 1,159
Likes: 0
Received 0 Likes on 0 Posts
Is the engine fully warmed up and only operating on 1/2 choke? The engine still might be a little cold. My engine runs like a turd when its cold (0* and below) until it warms up.

Otherwise it could be a mixture adjustment. Are you sure your float is adjusted right? Mixture screws adjusted right? Power valve ruptured?

How much vacuum are you getting at idle?

Also, what color are your plugs?
 
  #3  
Old 03-07-2011, 10:34 PM
fmc400's Avatar
fmc400
fmc400 is offline
MSEE
Join Date: Apr 2004
Location: Austin, TX
Posts: 10,386
Likes: 0
Received 22 Likes on 18 Posts
This is due to a lean condition, either because of a vacuum leak, or faulty accelerator pump.

With the engine off, look down the throat of the carburetor and actuate the throttle. You should see a nice stream of gas shoot against the venturi. If not, check that the accelerator pump and lifter link are properly assembled inside the carburetor.

Check for a vacuum leak by idling the engine and spraying for suspect areas with a can of carb cleaner spray, and listening for a jump in the idle speed. If this happens, the area you sprayed is leaking vacuum. Common areas include the carburetor base gasket, cracked vacuum hoses, and the brake booster. Sometimes you have to lean out the engine such that it just barely idles so that you can hear the jump. A vacuum leak will also be revealed by measuring the vacuum level at idle as wyckedcombo has suggested.

The reason choking the engine improves the problem is because it enriches the combustion mixture, which helps compensate the lean condition caused by the weak accelerator pump or vacuum leak.

Originally Posted by wyckedcombo17
Otherwise it could be a mixture adjustment. Are you sure your float is adjusted right? Mixture screws adjusted right? Power valve ruptured?
Just a side note: Carter 1-barrel carburetors do not have a power valve; instead they have a single metering rod.
 
  #4  
Old 03-08-2011, 04:44 AM
Talltruck's Avatar
Talltruck
Talltruck is offline
Senior User
Join Date: Dec 2002
Location: SW Florida
Posts: 473
Likes: 0
Received 0 Likes on 0 Posts
Another possibility is that something is blocking your main jet or the passageway to it. Especially with a 1 barrel, if any trash/dirt/piece of old gasket, etc. blocks or partially blocks it will make the motor go lean.

You really have to make sure all the passages in the carb are clean. Today's gas is really bad about gelling if it sits for very long, so when the carb is apart you have to make sure you clean everything using compressed air to blow out all the little ports to make sure it's absolutely clean inside.
 
  #5  
Old 03-08-2011, 08:47 AM
fmc400's Avatar
fmc400
fmc400 is offline
MSEE
Join Date: Apr 2004
Location: Austin, TX
Posts: 10,386
Likes: 0
Received 22 Likes on 18 Posts
Originally Posted by Talltruck
You really have to make sure all the passages in the carb are clean. Today's gas is really bad about gelling if it sits for very long, so when the carb is apart you have to make sure you clean everything using compressed air to blow out all the little ports to make sure it's absolutely clean inside.
Great advice. When you rebuilt the carburetor, did you do the full job (completely disassembling the carburetor, soaking metal parts in Chem Dip, spraying them clean, and blowing out the internal passageways with compressed air once dry)?

Anything short of that will often cause more issues than there were to begin with. The reason I ask is because when I hear the term "throw a kit in it," I think of the carb simply being sprayed down with a can of spray cleaner and closed back up with new seals. That won't work.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bfricks
1973 - 1979 F-100 & Larger F-Series Trucks
10
12-20-2016 02:33 PM
xtal_01
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
2
12-05-2016 09:53 AM
Bozworth
Ford Inline Six, 200, 250, 4.9L / 300
12
11-04-2013 01:41 PM
86rustbucket
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
5
03-13-2008 06:41 PM
pbuffing
1973 - 1979 F-100 & Larger F-Series Trucks
8
10-03-2005 02:13 AM


Thread Tools
Search this Thread
Quick Reply: carb poops out? why i ask. 300 6 cyl.



All times are GMT -5. The time now is 06:48 PM.