Autolite 4100 stalling issue

Autolite 4100 stalling issue

Joined: April 21st, 2010, 11:09 pm

March 29th, 2011, 10:21 pm #1

Good morning everybody.

I last winter I replaced the carb of my Ford Mustang GT 1966 with a rebuild Autolite 4100 from Pony Carburetors (I sent them an email too). I also replaced some fuel lines and filters. Everything worked perfect. I installed the carb with "factory" settings and I was ready to drive. The car was runing smooth and the fuel consumption was considerably lower.

Two weeks ago I woke up my pony from his winter sleep and suddenly I have the following problem (and it's getting worse):
When I drive the car on a flat and straight road at higher RPMs at about 40-50 mph and take the foot from the gas for 5-10 seconds and then press the gas pedal again the engine starts to stutter and almost dies. It's like a big "hole" - no power just a shaking.
When I keep the gas pedal pressed, the car will not accelerate. I have to take the foot from the gas and *gently, gently* press it again to speed up.
It only happens on a warm engine. The choke seems to work well. Outside temperature here is about 60°F at the moment.

First the problem only occurred 1-2 times every drive but now it seems it is getting worse. The stalling is longer and sometimes I have to depress and press the gas pedal 3-4 times to accelerate again. And today the engine died on a flat road!

Could this be a timing problem? (I have an Pertronix system installed). I didn't check the timing till now.
What could have changed over the winter time? Gaskets? Vacuum?

As everything was working marvelous last summer, I guess it can't be a floating level problem. The accelerator pump?
Is there a way to determine if the engine is getting to much or to less fuel?

As I am new to carburetors please excuse my (maybe) stupid questions.

TIA

Matthias
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Joined: January 1st, 1970, 12:00 am

March 29th, 2011, 11:20 pm #2

....the ethanol in the fuel at the pump often deteriorates accelerator pumps and power valves.
it also tends to clean the junk out of the fuel tank and this junk gets pushed into the carb and clogs stuff up.

If you have a warranty I'd purse it.

Other wise the carb will need to be removed, cleaned, and rebuilt.


Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a hipo 390, 780CFM 3310 holley, trick C6, Crites Aluminum radiator, California rear floor pan, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum athttp://network54.com/forum/88781
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Joined: April 21st, 2010, 11:09 pm

March 31st, 2011, 11:45 pm #3

Hi Ed

Thank you for your answer. I will try and do as you said.
Yesterday I did some bench and in-chassis adjustments (somehow one mixture screw was set very lean). At first glance, the engine runs way much better. But I didn't have time for a big test drive. I'll do a longer drive on Sunday and let you know, how it looks.

Matthias

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Joined: April 21st, 2010, 11:09 pm

April 17th, 2011, 7:38 pm #4

Hello Ed

I just cleaned my carb completely. But my problem did not disappear completely. At least the engine doesn't die any more. There is still a small but sensible acceleration-"hole". I double checked the floating levels. Could it be a problem of the vacuum advance unit? Where should I look next?

TIA

Matthias
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Joined: January 1st, 1970, 12:00 am

April 20th, 2011, 12:46 am #5

........the simple test is to pull the cap off (mark location of cap first), pull the vacuum line off the carb and suck on the line to see if it holds. or you can use a hand held vacuum pump. The diaphragm in these can rupture or leak.

It could also be accelerator pump related. you can try repositioning accel pump linkage in different holes on the throttle linkage. usually up or down from the current position.

Also the fuel we currently use is different from the fuel the carb was designed for, in a lot of cases the fuel contains ethanol so it takes more fuel to make the same power as regular old gasoline. I often set floats a bit higher then stock
(1/16") and increase jet sizes (one size up should do it).

It is really important to have the booster venturis as clean as possible on these carbs, lots of little holes to clog up.

Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a hipo 390, 780CFM 3310 holley, trick C6, Crites Aluminum radiator, California rear floor pan, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum athttp://network54.com/forum/88781
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Joined: April 21st, 2010, 11:09 pm

April 20th, 2011, 7:30 am #6

Good morning Ed.

Thank you very much for your answer.
Yesterday I gave it another try.... I readjusted the carb again according to the shop manual - BUT I set the floats higher and used a bigger jet). I noticed that the engine runs very smooth but the warmer it gets it starts to run very rich (much black smoke)! And in the end the RPM drops and the engine dies. I did the carb adjustments on a warm engine (10 minutes running on idle speed). The actual problem starts about 10 minutes later. Afterwards I decided to do a longer testdrive.... it's getting worse. I conclude my engine gets a way to rich mixture (the black/brown spark plugs seem to suppport my guess).
I also called a friend who owns a ford garage. He normally takes care of my Mustang but he's on holiday right now: He suspects a faulty motorblock gasket somewhere (intake manifold?). Would this explain the coherence with the temperature?

During the next days I'll do the tests and modifications you suggested in your last post.

I'm also thinking about testing my Mustang with my other (old) Autolite 4100.

I'll keep you updated.

Matthias

P.S. If some Pony Carb guy would read my post: thank you for NOT answering my emails!
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Joined: January 1st, 1970, 12:00 am

April 27th, 2011, 12:44 am #7

........might want to lean the mix out a small amount too. Sometimes its trial and error on this old cars

Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a hipo 390, 780CFM 3310 holley, trick C6, Crites Aluminum radiator, California rear floor pan, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum athttp://network54.com/forum/88781
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Joined: April 21st, 2010, 11:09 pm

April 27th, 2011, 10:17 am #8

Hello Ed

I gave my carb another try.... and I think I found something interesting:

When I opened the air horn, I immediately discovered that the primary fuel bowl was almost empty! (the car was parked for about 20 hours) Does this explain my problem? Whenever I start the car, I have a black and oily sauce comming out of both exhausts and I have to keep the pedal pressed to keep the engine running in the first 10-20 seconds.

My fuel seems to be leaking into the intake manifold(?)

Where should I start my search? Which one is th faulty component?

Would this fuel leak explain all my problems? Or do you expect more?

TIA

Matthias
Last edited by Quaksalber on April 27th, 2011, 10:18 am, edited 1 time in total.
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Joined: January 1st, 1970, 12:00 am

April 28th, 2011, 12:21 am #9

.........did you test the wet float level?

the fuel could have evaporated after 20 hours of sitting

Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a hipo 390, 780CFM 3310 holley, trick C6, Crites Aluminum radiator, California rear floor pan, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum ahttp://network54.com/forum/88781
Last edited by Galaxie on April 28th, 2011, 12:21 am, edited 1 time in total.
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Joined: January 1st, 1970, 12:00 am

May 4th, 2011, 5:04 pm #10

Good morning Ed.

Thank you very much for your answer.
Yesterday I gave it another try.... I readjusted the carb again according to the shop manual - BUT I set the floats higher and used a bigger jet). I noticed that the engine runs very smooth but the warmer it gets it starts to run very rich (much black smoke)! And in the end the RPM drops and the engine dies. I did the carb adjustments on a warm engine (10 minutes running on idle speed). The actual problem starts about 10 minutes later. Afterwards I decided to do a longer testdrive.... it's getting worse. I conclude my engine gets a way to rich mixture (the black/brown spark plugs seem to suppport my guess).
I also called a friend who owns a ford garage. He normally takes care of my Mustang but he's on holiday right now: He suspects a faulty motorblock gasket somewhere (intake manifold?). Would this explain the coherence with the temperature?

During the next days I'll do the tests and modifications you suggested in your last post.

I'm also thinking about testing my Mustang with my other (old) Autolite 4100.

I'll keep you updated.

Matthias

P.S. If some Pony Carb guy would read my post: thank you for NOT answering my emails!
.........as a ruptured power valve could cause a rich condition, and an empty float bowl.

Also check the power valve torque, sometimes the gasket does not seat correctly and will leak.

Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a hipo 390, 780CFM 3310 holley, trick C6, Crites Aluminum radiator, California rear floor pan, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum athttp://network54.com/forum/88781
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