Autolite 1100 - PULLING MY HAIR OUT!!!

[matthewfrance]

I have a 1966 Mustang with an Autolite 1100. I sent the carb and had it rebuilt by a reputable company in Washington state. No real issues before the rebuild except a "flat spot" I'd sometimes notice when accelerating and it was very stained. The carb came back looking great as expected. I installed the carb and at the same time changed plugs (gapped to .034) plug wires, dist. cap and rotor, and oil/filter (as the car had been siting in the garage for a few months.) The car started fine, and idled well - I then noticed the fuel pump was leaking, so I shut the car off (before it warmed up) and replaced the pump as well. Restarted the car and idles great cold and warm.
My problem is:
When I quickly open the throttle from idle when the engine is warm and choke is open, the car stumbles and stalls - if I let off as it begins to stumble, it will return to idle. I can slowly open the throttle and the engine will smoothly rev without stalling. If the choke is closed, it will rev quickly just as you'd expect - it only begins to stumble after its at normal operating temp.
Things I've tried:
Checked/adjusted float level +-1/16" from specs - no change - went back to original 1 3/32"
Checked accelerator pump diaphragm and confirmed correct measurement between roll pin and diaphragm cover (3/16" if I remember correctly)
Tried moving roll pin to "lo" position on accelerator pump lever
Adjusted vent valve rod so notch lines up with valve port
Confirmed suggested mixture screw setting (1 1/2 turns out from lightly seated) and experimented turning it both ways Confirmed check balls and weight were installed and used compressed air to clean passages
Confirmed dashpot setting (lightly seated plus 3 1/2 turns in)
Changed jet from 69 to Ford manual suggested 67
Checked for vacuum leaks at bottom of carb
Checked timing and experimented from +12 to +16 with no noticeable change
Ran brand new fuel from gas cam straight to fuel pump
Changed plugs again (ones that came out were covered in black carbon)

I've had the carb on and off the car and opened up probably 10 times - I checked/recheckedfloat level and smooth needle operation several times- I've even changed the accelerator pump diaphragm (even though the one that came out was brand new and looked fine)

I'm stumped....I need some help from all you guys that are way smarter with more experience!
Thank You in advance!

 

[wsa111]

First welcome aboard. I approved your post since you seem to have a urgent response.
Are you seeing a visible shot of fuel when you open the throttle??
If so lets look at your loadamatic distributor vacuum advance.
If you put a timing light on the tab do you see any movement of advance when opening the throttle??
You say it stumbles, do you have another coil to see if its an ignition related condition.
Advance the initial 6 degrees above factory settings & see if that helps?
Keep in touch.

 

[matthewfrance]

Thank you for the quick help!
The timing definitely advances when revved....to somewhere about 12:00 on the balancer...I went ahead and set it at 16degrees at idle.

As for the squirt...I let the engine idle for 30 seconds or so, killed it, and then pushed the accelerator pump while holding the choke open and looking down into the carb... I'm not sure which orifice I'm looking for the squirt to come from, but if it's supposed to be very noticeable, then I have no squirt! Should I take it apart and check for blockages?

Thank you again!

 

[matthewfrance]

I removed the carb and took the air horn off - I removed the check balls and weight and blew compressed air through every orifice, especially around the accelerator pump - all seemed clean and passed air. Put the carb back on the car and I'm still having the same problem...I've looked again for the squirt from the small orifice near the top of the air horn and I still don't see a squirt - air was definitely passing through, though. Any other ideas?
Thanks again!

 

[wsa111]

You have a problem with the accerator pump circuit. You need to make to be sure the gasket between the top cover & bowl is allowing the pump shot from the body to the top cover has an orifice allowing the fuel to exit from the pump orifice??

 

[B RON CO]

Hi, X2 on the accelerator pump malfunction. On any carb, when you pump the gas, engine off, hot or cold, there should be a very noticeable squirt down the center of the carb. This richens the mixture so the engine doesn't stumble. Why don't you talk to the guy who rebuilt the carb and tell him what you see? A lot of us would just rebuild it ourselves. The rebuild kit comes with clear instructions on settings and reassembly. As mentioned, something on your accelerator pump is out of whack. Good luck

 

[ledslinger29]

Are 1100s supposed to leak around that plastic rod that operates the accelerator pump?

 

[chad]

choke operation correctly?
deff too rich w/those sooty plugs.
My YF has steps or fingers on the linkage (external to the carb) that U can observe as engine temp rises.
Should go frm 1 or the other step to next to 'free' of them all when warmed up (@ 7 min mark).

No, acc pump rod bushings do not leak unless aged and worn - a very typical prob.

 

[B RON CO]

Hi, if fuel is leaking out the top of the carb you should not run the engine at all. There is no way fuel should get "up there" It could be, excessive fuel pressure, bad or dirty needle and seat, bad or wrong adjustment on the float. Maybe you got debris from somewhere in there. Is it possible the top gasket is on upside down? I'm really reaching with that question. I would talk to the guy who rebuilt it for you. Maybe they will exchange it for you. Carbs need to be treated with a gentle touch. Good luck