carb troubles on an 8BA

banjoQ

banjoQ

Senior Member
I have an 8BA with a Ford 94 carb marked 8BA on the left side. This carb was rebuilt 10 mos. ago. It has developed a bad stumble right off idle that has me puzzled. Up until yesterdays drive the carb and motor have been running smoothly. Some background on my setup, new tank, fuel supply line and fuel pump and the rebuild on the carb. I have gone through the electrical, have spark in all holes. Truck starts fine, idles fine and revs up when you stab the throttle. When you move the throttle linkage by hand you can see that it problem develops right off idle. Further movement, more gas and it powers through it. Difficulty holding a steady, moderate speed. Accelerator pump is giving a good squirt, fuel pump bowl is clean and pump provides good pressure. Are there any components inside the carb that could have failed that would cause these symptoms? I must admit, I have been procrastinating about putting in an inline fuel filter. I will do it now that I have to dig into this problem. I did not do the rebuild on the carb, farmed it out to a highly regarded shop here in the Bay Area. Any thoughts on where I might look to fix this or should I start thinking about another rebuild. Thanks-Q
 
Banjo, a stumble or hesitation right off idle sounds like a partial blockage of one of the main jets. Not having a fuel filter lends to this theory also. Try checking the jets for debris and you may get away without a rebuild. If you remove a jet for inspection, take care that the bowl is clean prior, to avoid allowing debris into the fuel passage.
 
Ford38V8- Thanks for the reply. That is as good a place as any to start. I am guessing that I will have to remove the carb for this one. Do I need to dis-assemble to get to these main jets? Any special tools required? Afraid I am not to experienced with carbs, but willing to learn. In the meantime, I will break out the books and see what I can come up with. Thnx-Q
 
Is there any slop in the accel pump linkage? You say it has a good squirt, but if you have to move the throttle a while before it starts to squirt, that's no good.

What RPM do you have it idling at? If it's too slow, it can cause a situation like you describe.

Was yesterday's drive the first since the weather turned? It could be you had adequate squirt for warmer weather, but not enough for cold weather. There are three holes for the accel pump linkage; summer, Normal, and Winter. See which hole the rod is in.
 

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Ross- I went out and checked the setting on the linkage for the accelerator pump. Currently it is in the middle position. We don't really get real cold weather here. There is no slop in the linkage to the accel.pump, pretty good actually. The truck gets driven several times a week, often 40mi. or so. The stumbling came on in the middle of my trip. Can't help but think that the ten bucks worth of gas might be a contributing factor. Believe me, I will be putting an inline filter in. I will try moving to the winter position and see if that changes things. Can anyone talk me through removing and inspecting the main jets?
 
A main jet problem wouldn't have the symptoms you describe. It would be more evident at higher fuel flow rates.

It's very common for problems after a fuel fill, as it stirs up crap in the tank.
 
Banjo, the removal of the main jets in your case, to inspect for debris, should not be done while the air horn is in place, for the reason that the debris may migrate beyond the main jets upon their removal. So.... , for this reason, start by removing the air horn, taking care to salvage the gasket if you have no replacement. No need to remove the carb from the engine.

The air horn carefully set aside, the fuel bowl will be exposed, along with the debris at the bottom. The two brass plugs removed from the exterior of the bowl will drain and flush the bowl, exposing the main jets, accessible from the drain holes.

After flushing the bowl through the plug holes, a screwdriver with narrow shoulders will remove the jets, or, just confirm that they are clear with a fine bristle of a broomstraw. The use of wire is not a good idea, as it could bring up a burr on the casting.

Replace as removed (with the forethought of filling the fuel bowl first), with care for the integrity of the gasket and plug washers. If the gasket is damaged, it must be replaced. Do not use sealant or teflon tape anywhere. Test all fuel connections before your test drive by starting the engine, and shutting down, observing the connection between pump and carb for fuel leaks. None found, your test drive can begin.
 
Ross F-1 said:
A main jet problem wouldn't have the symptoms you describe. It would be more evident at higher fuel flow rates.

It's very common for problems after a fuel fill, as it stirs up crap in the tank.
Click to expand...

Ross, with due respect, you contradict yourself. Debris in the fuel bowl is the suspected cause of the stumble, at relative rest while at idle, at the bottom next to the jets.
 
Thanks guys, good ideas and very helpful information. I will get on this tomorrow and report back. I feel better already. Q
 
You could have a leaky power valve,rubber accelerator pump and or faulty inlet needle [rubber tipped]. Depends what kind of kit was used on the rebuild?? An 8BA engine comes with a glass bowl and a modern paper filter can be fitted in it. It could be the pump or and the carb both. Call me i'll see if I can help. ken ct 1-203-260-5945 cell.
 
Banjo,
While the carb is off be sure to remove the squirter between the two
nozzle bars. Beneath the squirter is a brass pin which is removed by flipping the
carb over. The pointed end of this pin goes into its bore first and males a check
valve of sorts on a machined face at the base of its bore. Any dirt or deep nicks
that keeps this thing from sealing will cause your problem. After a clean up reinstall
the pin and with a small punch and a TINY hammer give the pin a boink to insure it
is seated. The pin must seal but also work freely in the bore.
While the squirter is in your hand make sure both orifices are open fully. My
scientific way of doing this is to attach a piece of small diameter hose to the stem
and with lung power blow into the other end of the hose while the squirter is
submerged in some non lethal liquid. The volume of bubbles should be the same from
each orifice.
The last item I'll drag you thru is the ball check at the bottom of the acc pump
bore. If dirt has found its way beneath this tiny ball it will not seal fully. The ball
when working properly keeps fuel from escaping when the acc pump is actuated.
When this ball is not sealing as it should fuel is pushed back into the bowl and not
100% thru the squirter.
In most cases the middle hole is where you want the link.
Charlie ny
 
Charlie ny said:
Banjo,
While the carb is off be sure to remove the squirter between the two
nozzle bars. Beneath the squirter is a brass pin which is removed by flipping the
carb over. The pointed end of this pin goes into its bore first and males a check
valve of sorts on a machined face at the base of its bore. Any dirt or deep nicks
that keeps this thing from sealing will cause your problem. After a clean up reinstall
the pin and with a small punch and a TINY hammer give the pin a boink to insure it
is seated. The pin must seal but also work freely in the bore.
While the squirter is in your hand make sure both orifices are open fully. My
scientific way of doing this is to attach a piece of small diameter hose to the stem
and with lung power blow into the other end of the hose while the squirter is
submerged in some non lethal liquid. The volume of bubbles should be the same from
each orifice.
The last item I'll drag you thru is the ball check at the bottom of the acc pump
bore. If dirt has found its way beneath this tiny ball it will not seal fully. The ball
when working properly keeps fuel from escaping when the acc pump is actuated.
When this ball is not sealing as it should fuel is pushed back into the bowl and not
100% thru the squirter.
In most cases the middle hole is where you want the link.
Charlie ny
Click to expand...
All good points Charlie,but he admits hes not too carb savy maybe he shouldn't mess with it,i'll help him over the phone as much as I can and I know you will too,hope he finds whats wrong. ken ct.
 
Charlie ny said:
Banjo,
While the carb is off be sure to remove the squirter between the two
nozzle bars. Beneath the squirter is a brass pin which is removed by flipping the
carb over. The pointed end of this pin goes into its bore first and males a check
valve of sorts on a machined face at the base of its bore. Any dirt or deep nicks
that keeps this thing from sealing will cause your problem. After a clean up reinstall
the pin and with a small punch and a TINY hammer give the pin a boink to insure it
is seated. The pin must seal but also work freely in the bore.
While the squirter is in your hand make sure both orifices are open fully. My
scientific way of doing this is to attach a piece of small diameter hose to the stem
and with lung power blow into the other end of the hose while the squirter is
submerged in some non lethal liquid. The volume of bubbles should be the same from
each orifice.
The last item I'll drag you thru is the ball check at the bottom of the acc pump
bore. If dirt has found its way beneath this tiny ball it will not seal fully. The ball
when working properly keeps fuel from escaping when the acc pump is actuated.
When this ball is not sealing as it should fuel is pushed back into the bowl and not
100% thru the squirter.
In most cases the middle hole is where you want the link.
Charlie ny
Click to expand...
I had to LOL on how you test the squirter,i inserta needle blowgun tip and blow 175# air pressure through it you can feel the air stream coming out real good at that pressure, only my way of doing things. More snow coming Charlie be careful out there. ken ct.
 
I just stick the nozzle of a carb cleaner can in the bottom of the squirter and give it a shot. You can easily tell if the shooters are clear and equal.
 
Guys,
The non lethal liquid I prefer....sometimes frequently....is Jamesons 12 year
old unblended whiskey. The carb cleaner just tastes horrid and doesn't mix well with
a dash of water.
Charlie ny
 
This is how I would do it .Your problem sounds like its in the idle circuit , remove the top and all the jets squitter and idle mixture screws ,get a compressor with a air gun and blow through all the holes with 100 psi compressed air,
 
Hey, one thing at a time, guys! It's not rocket science, but the guy is a newbie with carbs, so you don't want to overwhelm him right off the bat. Let him do the simple bowl flush before you entice him to get in over his head.

Charlie, good idea on the boink to the squirt valve, which points up the vulnerability of the casting to damage from tools and mishandling, the reason I shy away from using wire to verify passages. Once Banjo gets that far, however, he'll be a carburetor guru himself! :D
 
Alan you cant get a wire through that passage in the first place it makes a rt angle turn to the accel pump passage [the other hole in the bottom of the pump hole w/o the ball in it] All you can do with that one is blow it out w/lots of air pressure.
 
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