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jfh
05-07-2007, 07:11 AM
Just rebuilt my 4 barrel Carter AFB. On start up I could not keep it running. My mechanic says that the injection pumpseal(the leather one at the bottom of pump)made contact with fuel and curled up thus not creating a seal. He said I should have prepped it with vasoline. Is this normal? He also suggests finding an injector pump with rubber seal, does anyone know if one is available?

DEEPNHOCK
05-07-2007, 08:42 AM
The correct term is 'accelerator pump'.
It is usually supplied in a carburetor rebild kit.
A carb rebuilder will probably have them in bulk.
Vaseline might not be the best choice if the seal is leather.
Neatsfoot oil might be better, but only to supple up a dried out leather seal. A nitrile rubber seal might be better than leather, and Vaseline might be bad for that, too..
I wonder about the 'making contact with the fuel' statement.
The accellerator pump should be wet with fuel 'all the time' (at least on one side of the piston seal)...
Allowing it to 'dry out' (setting a long time) would cause problems, but they would/should disappear after the fuel pump pushes fuel up into the carb, and into the accelerator pump area.
Now, saying that....
Pumping the accelerator pedal a whole bunch of times on a dry carb (stored a long time) may be real hard on the accelerator pump piston, as you are now dragging a dry piston up and down in a dry bore.
Allowing the fuel pump to pump some fuel up into the carb is a good idea.
Then pump the pedal.
(If your starter and battery can stand it).
Hope the info helps..
Jeff[8D]


quote:Originally posted by jfh

Just rebuilt my 4 barrel Carter AFB. On start up I could not keep it running. My mechanic says that the injection pumpseal(the leather one at the bottom of pump)made contact with fuel and curled up thus not creating a seal. He said I should have prepped it with vasoline. Is this normal? He also suggests finding an injector pump with rubber seal, does anyone know if one is available?


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jfh
05-07-2007, 09:10 AM
Jeff, Thanks for the info..your right the correct term is accelerator pump. The rebuild kit I bought supplied the pump unit, and the gas evidently caused it to curl. The old one I removed was also of leather and it sat for 30 yrs and did not curl, could I have a defective pump?
Thanks Joe

John Kirchhoff
05-07-2007, 10:26 AM
Having an inoperative accelerator pump shouldn't keep the car from continuing to run. The only time it plays an active role is when you stomp on the gas pedal. When you do, the vacuum drops, the carb doesn't suck enough gas and the engine stumbles. The accerator pump squirts a shot of gas into the carb, which richens up the mixture and prevents the momentary stumble. Even without an accerator pump, the engine would eventually regain vacuum appropriate to the throttle opening and run fine. Incidently, the 225 and 318 Chrysler engines on my combines don't have accerator pumps on the carbs and they run fine.

If you can't keep the engine running, I'd be looking at something other than the accelerator pump. A quick way to find out if it's starving for fuel is to get it going and squirt little shots of starting fluid into the carb. If it smooths out, it's running too lean. If it runs worse, it's likely running too rich. If it doesn't act much different, better start looking at other possibilities.

John Kirchhoff
05-07-2007, 10:33 AM
Oh, no offense intended, but I think your "mechanic" either jumped to conclusions, isn't trained or experienced with "old fashioned" carbs or just plain doesn't understand how such things actually work. Without the the latter, troubleshooting and repairing problems is a shot in the dark affair.

jfh
05-07-2007, 02:16 PM
John,
I can keep the car running only if I give her a shot of starting fluid, Then I have to keep the throttle up until she warms, up then she will idle on her own. I just examined the old accelorator pump and it was leather and sealed fine.Think I could have installed it wrong? Maybe I didnt quite get it seated and gas was pumped in , leather swelled and it rolled outward on the first few pumps.

showbizkid
05-07-2007, 07:52 PM
IMHO, sounds like the choke plate is not set correctly. If the plate closes too tightly when the choke is set and does not allow enough air to enter the carb, you'll get the symptom you're describing. I'd double-check the cold clearance for the choke plate and reset if needed.


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Dick Steinkamp
05-07-2007, 08:30 PM
quote:Originally posted by jfh

John,
I can keep the car running only if I give her a shot of starting fluid, Then I have to keep the throttle up until she warms, up then she will idle on her own.


As mentioned, this symptom has nothing to do with the accelerator pump. I'd say your choke is not adjusted correctly or is not working correctly.

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John Kirchhoff
05-07-2007, 10:17 PM
As the other folks said, I'd check the choke. You might make sure the choke plate closes completely when the engine is cold. Don't forget that after having been warmed up and fully open and then cooling off, some carbs need to have the throttle opened up just a bit to allow the choke to close completely. While you have the air cleaner off, get it going and observe the choke plate. Very shortly after the engine starts running, the choke should open up a bit as the little vacuum diaphram does it's duty (never worked on an AFB, so I assume it has one). If the choke is running too rich, the engine will be fine immediately at starting but then start loping and chuffing out black smoke. Take our finger and push the choke open some and see it it starts running better and if so, it's not opening up quickly enough. However, from the symptoms you describe, it sounds as though it's not getting enough fuel when cold. Try pushing the choke plate nearly but not completely shut with your finger and see it things improve. If so, it would lead me to think the choke is simply out of adjustment unlike a rich mixture which could be one of several reasons. Just remember that as the engine warms up, lean conditions run better and rich conditions run worse.

If the choke is closing all the way and seems to be doing what it's supposed to be doing, there's the possibility that an idle circuit is plugged up. I've had that happen a couple of times with combines. They have a manual choke and it was required to use lots of it until the engine got warmed up and then they'd seem to run fine. Each time I disassembled the carb and it was the fuzz off of soybeans. As fuel was pulled from the tank, dirty air was pulled in and I suspect that's how it got in there. That nasty stuff can make it past a sediment bowl AND inline filter and end up in the carb. No wonder it makes me wheeze.

In the 70's, certain Chrysler carbs (Holleys?) used a phenolic resin in carb body parts. That stuff was good about distorting and then cause the choke shaft to bind up. Sometimes they'd run rich or lean, it all depended upon the position when they got stuck. You might make sure the choke shaft turns freely.

Something else I just though of, check the throttle shaft (the one that's connected to the gas pedal) for play. When worn enough, they'll suck enough air to really lean out the mixture. When that's the case, the engine will usually run pretty good at high speeds but badly at idle.

showbizkid
05-08-2007, 07:18 PM
quote:Originally posted by John Kirchhoff

In the 70's, certain Chrysler carbs (Holleys?) used a phenolic resin in carb body parts.

I think you're thinking of the Carter Thermoquad.


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John Kirchhoff
05-08-2007, 09:45 PM
jfh, you might keep in mind that sometimes carburation problems are actually ignition related. A powerful ignition with a wide plug gap can ignite some pretty messed up mixtures while a weak ignition needs everything perfect. If it's a tad rich or lean, problems arise. If fiddling with the carb doesn't make any difference or only marginal improvment, you might look at the ignition.