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scoryell21

1969 Mustang 428 hesitation

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I have just finished restoring a 1969 GT 428CJ and took it out for its first big road trip this past weekend. I had ran it up and down the highway before the trip a few times the and had over 100 miles on it and everything seemed fine, I put over 200 miles on it on this trip and I started to notice a bog right during acceleration in any gear. Most noticeably from a stop, it almost dies going through an intersection but then picks up and runs fine. Even at 70mph and in 4th gear if I let off the gas and get back on it quickly the bog is there but not so much if I roll through the acceleration. I did not notice this when first running it in the days prior but after getting on it and really running it for a day it showed up. I have checked the vacuum lines and all seems well. I have read some information that it could be the accelerator pump or even the squirters? Any thoughts or information would be great.

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Start with the easy stuff. My timing is set at 14 degrees and actual is 34. Pull a couple plugs to see how they look. Check your fuel mixture screws. If you think it is the carb. see about borrowing one and switch it. Hey the car is running and you just need to dial it in. You'll get it. Brian

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Is the carb fresh? Sounds like an accelerator pump issue to me. With engine off, look down the throat of the carb while opening the throttle . You should see two steady streams of fuel in each of the primary venturi.

 

If not you have a problem. You may have a ruptured/torn accelerator pump gasket.

 

Any signs of fuel weeping at the front of the carb?

 

John

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I had similar problems with my CJ. A combination of two things were discovered.

1. The fuel line from the pump to carb had an inline glass bulb fuel filter. The car ran fine with it before the rebuild but after, it caused stalling problems. Removed the inline filter solved the problem. Even though I removed the filter it was still causing vapor lock.

2. The second performance issue occurred from a fuel pump issue. I finally tore it down to find the diaphram had dry rotted along one part of the outer edge.

 

Hope this helps

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Thank you for the help everyone. I found and fixed the problem! The previous owner had done some modifications and it has a '70 spacer plate with a 1/2 hose coming from the PCV valve into the spacer plate, the plastic nipple on the spacer plate was broken, I fixed that and took it down the road and the problem seems to have gone away.

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