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I just bought a 66 Mustang, 289, with a 750 Holly and msd ignition. I had it shipped over from michigan. When I start it it will run for about 20 seconds and then starve and die. I can have it at idle or revved to 3 grand and it will still die. It does better in neutral or park but as soon as I try to get it into gear the idle has gone top low and it dies. After it dies I have to let it sit or it is hard to start or only sputters. Give it a minute and it will start and run for another 20 seconds. It is a manual fuel pump. The clear horizontal fuel filter looks fine at 2/3 full the whole time the car is running and after, there is a sound of liquid trickling for maybe 7-10 seconds after the car dies(maybe fuel returning to lines or air escaping lines??). Could this be a vacuum leak, carb issue or fuel pump? what order/how should I go about testing these issues. Thanks!
 

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It sounds like the float is set too low in carb or vacuum leaks.
On the side of the float bowel is a plug, remove plug, start engine and adjust float at the screw jam nut on the top of the bowel until fuel comes out the plug you removed. With the engine off, can you see a stream of fuel go into the carb when you hit the gas? You may have to have the carb rebuilt but it sounds like a carb problem if you can see fuel in the filter at all times.
 

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First off the carb can't suck fuel out of the fuel filter, Some tests should be performed, fuel pump capacity test is by grounding the high voltage coil wire, remove the fuel line from the carb, put on a piece of rubber fuel line on it and the other in a metal can at least a quart size, crank the engine for 20 seconds, you should have at least a pint of fuel in the can, if you don't then, you could have a clogged sock filter in the tank, bad rubber hose from the tank, crimped fuel line under the car, bad fuel pump, bad fuel pump eccentric, clogged clear fuel filter. If you had enough fuel in the can, then you need to open the fuel adjustment site holes, and see if fuel is getting into the carb, Holly's are great carbs, but if they have had gas in them, and then allowed to set and dry out the cork gaskets inside them crack and shrink and cause alot of problems. Post your results. Good Luck.
 

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First off the carb can't suck fuel out of the fuel filter, Some tests should be performed, fuel pump capacity test is by grounding the high voltage coil wire,

To ground it just take it out of the dist cap and ground it to the car? Thanks!
 

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You want to ground it to keep the engine from starting, and second so a spark is not produced, since you will have gas in an open can.
 

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First off the carb can't suck fuel out of the fuel filter, Some tests should be performed, fuel pump capacity test is by grounding the high voltage coil wire, remove the fuel line from the carb, put on a piece of rubber fuel line on it and the other in a metal can at least a quart size, crank the engine for 20 seconds, you should have at least a pint of fuel in the can, if you don't then, you could have a clogged sock filter in the tank, bad rubber hose from the tank, crimped fuel line under the car, bad fuel pump, bad fuel pump eccentric, clogged clear fuel filter. If you had enough fuel in the can, then you need to open the fuel adjustment site holes, and see if fuel is getting into the carb, Holly's are great carbs, but if they have had gas in them, and then allowed to set and dry out the cork gaskets inside them crack and shrink and cause alot of problems. Post your results. Good Luck.

OK fuel is getting past the fuel filter at a good rate/pressure. I got it put back together and will dig into the carb tomorrow.

It is a Holly and was told a 750. The numbers I was able to pul off it are as follows:

on the side of the throat: 80506-3
1396

another number lower down: 10569

and on the top is the number 90 inside of a circle.

I do have a vacuum pressure gauge. What should I look at first? I have never done carb adjustments before. I have not looked at the float yet either. If you can spell out a checklist that would be great. Thanks again!
 

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The first thing I would check on the carb is the float setting, there is a brass screw-in plug on the side of the float bowls on the front and back of the carb, take one out (start with the front float), fuel should just trickle out of the hole with the engine running, if not the the adjustment is on top of the float housing, it takes a screwdriver and an open end wrench, you barely have to loosen the brass stop on top with a screwdriver, and turn the wrench on the nut a little, I think that clockwise will decrease the level and counter-clockwise will increase the level, then tighten the screw stop down there is a gasket under the stop, it will spew a little gas while running, or you can turn the engine off or dies, then make a small adjustment and start it back up, once you have done the front do the back one, I suspect the front float is stuck or not working properly, you can remove the needle and seat assembly from the float bowl thru that adjustment on the top, with the motor off, you can remove the stop, then use the wrench to back it out of the float bowl, there are thin gaskets here so pay attention to how they come off so you can put them back. There are other adjustments, but try this first. Post your results. Good Luck.
 
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