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Old 02/09/2019, 10:26 AM   #1

Location: Quebec, Canada
Joined: Jun 06
Posts: 332

Advice/help on carb hesitation, Vert 1973 351 Cleveland 2V


Need avice on my carb. This is a 1973 351 Cleveland 2V Auto.

In regular acceleration or drive, at about 40-45 mph, there is an hesitation, where it kind of stall and engine won't go faster unless I press hard on pedal.

Normally, I would just release a bit the pedal and accelerate further then it goes above this zone OK.

If I was to press very hard acceleration right from the start, I may avoid this stall, but in regular smooth accel or drive in the 40-50 mph cruise it is there every time I pass up this 40-45 mph, where then i release and re-accelerate pass this 40 mph barrier.

In looking for solutions, I read about potential "carb pump diaphragm" cause. Before I start to get parts, any advice on this, for causes and fixes.

Thanks so much.

Pierre gtcs1

1968 GT/CS - Highland Green - C Code 289
1973 Mustang Convertible - Bright Green Gold Metallic - H Code 351-2V
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Old 02/09/2019, 10:56 AM   #2
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GT/CS 8R01C150245

Location: Victoria, BC Canada
Joined: Jun 12
Posts: 1,519

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Might be too simple, but this sounds exactly like a 68 Coupe I used to own. It had a bad stumble when I was leaning into the accelerator coming off an idle. I put a bottle of gas treatment in the gas tank and sprayed carb cleaner into the carb a couple of days apart and the problem disappeared. I suspect it was a bit of gunk in one of the jets.

Steve Cracknell
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Old 02/09/2019, 01:04 PM   #3
robert campbell
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Location: Bremerton Washington
Joined: Apr 07
Posts: 4,055

My Garage
This sounds totally like accelerator pump failure. You are already going in that direction. Your accelerator pump diaphragm has a hole in it, is full of gunk, or the passages from the accelerator pump to the shooters in the venture may be plugged.

First thing is to take the air cleaner off and get a flashlight. Get something to lay on either over the massive fenders, or the long long nose of your Stang. Now climb up so you can look right down the throat of the carb with the choke flap open. Either have you lovely wife sit in the car and stab the throttle open, or work it with your third hand. One hand on the flashlight, one hand on the choke flap, and your foot opening the throttle in some sort of very weird yoga position.

You should see a strong shot of raw gas coming out of two small holes in what is called the "shooter". Down both throats. It should spray out in a nice thin solid line and not dribble out like an 80 year old guys "weiner".

Do this test and if you see just drips or nothing, you have found the problem. Post your results and we will go from there.

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Old 02/12/2019, 05:50 PM   #4

Location: Quebec, Canada
Joined: Jun 06
Posts: 332


Thanks for the good advice. Look forward to test that. My car is currently in storage till 2nd of april. As soon as I bring it back home, I'll test that and advise. I was just getting ready to know which way to go for when I have access to it.

Winter is here and not likely to go away. One of the worst winter for few decades. Like if itsn't enough, tonight a snow storm has started and we expect 18" of snow till tomorrow afternoon.

1968 GT/CS - Highland Green - C Code 289
1973 Mustang Convertible - Bright Green Gold Metallic - H Code 351-2V
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