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EFV-8 Club Forum / General Ford Discussion / Hesitation on acceleration

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Discussion Topic: Hesitation on acceleration

TomO

07-04-2012 @ 9:16 AM

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Pete, have you found your problem?

Tom

TomO

06-28-2012 @ 8:10 AM

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Pete,

There is a write up in the 49-51 Mercury Overhaul Manual on your carburetor. There is a column and a half on just checking the accelerator pump.

These are too long to type in and right now my scanner is out of service. I am in the process of upgrading to a more modern computer and along with my other work, I don't have time to copy this for you copy this for you. See if you can find some info locally on this.

One thing to check is do you have the nylon ball in the vacuum passage for the distributor advance?

To check the accelerator pump, use an allen wrench to press down on the pump discharge needle and then push down on the accelerator pump piston. If fuel is forced past the needle clean the needle seat. If bubbles appear from the pump intake hole or the fuel level in the bowl increases, clean the check valve ball and seat.

Here is a link to a diagram and specifications of your carburetor.

http://www.oldcarmanualproject.com/manuals/Carbs/Holley/885/index.htm

Tom

pnyce

06-27-2012 @ 10:23 AM

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All,

Thanks for your ideas. I'll check them out at my earliest opportunity, especially the check valve.

Pete

Thanks, Pete

supereal

06-27-2012 @ 9:02 AM

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Check to see what stroke the accelerator pump linkage is set. I set them on the longest stroke with the link in the hole farthest from the pivot point. On the coincentric carb, it is on the throttle linkage side, and fits into a rod leading up to the pump. There are two springs on the accelerator pump controls, one on the actuating rod, and another on the shaft of the pump, itself. If either of these springs is broken or weak, the pump will not have a full stroke. As said above, if the check ball in the bottom of the pump well is missing or not seating, there will be little or no fuel expelled from the discharge jets. If you need a diagram of the carb, I can post one.

TomO

06-27-2012 @ 7:32 AM

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The Holley Carburetor on your Mercury is different than the carburetor on the Fords.

Old Henry gave you good advice about checking the accelerator pump, but you will have to remove the air horn in order to see the squirt of gas. I would do this before dissembling the carburetor again.

Another common cause of the hesitation that you have is the distributor advance. Use your timing light to see if it is actually working. The Loadamatic distributor uses a combination of springs and vacuum to advance the spark.

I would also check for vacuum leaks.

Tom

This message was edited by TomO on 6-27-12 @ 7:40 AM

Old Henry

06-27-2012 @ 6:48 AM

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It's easy to check the acceleration pump by looking down into the carburetor while deflecting the throttle mechanism a little and look for the squirt of gas in the carburator throat. Saves guessing and wondering whether it's working.

Old Henry
(The older I get, the better old looks.)

oldford2

06-27-2012 @ 5:34 AM

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When you "rebuilt" the carb what did you do to the power valve? Replace/test it. On acceleration I believe the acc pump only gives a momentary squirt of fuel while the power valve opens to provide a steady stream of fuel. John

ford38v8

06-26-2012 @ 10:50 PM

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Pete, I think you nailed it. The fuel we get these days has caused many problems, one of which is sticky varnish. I think your pump ball is stuck. Did you remove and clean it and the passages when you rebuilt?

When cleaning those passages, never use wire, always bristle, as wire can easily scuff up a burr, which would block the passageway. Be sure that the bristle is still whole whe you are done, and blow through with compressed air to be sure of a free passageway.

You might also pull the leather piston and work it with oil. Leather is always the best choice, but oil can soften it up to insure a good seal against the wall. I doubt that the cylinder wall could be at fault.

Alan

This message was edited by ford38v8 on 6-26-12 @ 10:52 PM

pnyce

06-26-2012 @ 9:39 PM

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Hi,

I have a '51 Merc but I would think that my problem could effect any carburetored Ford product. I have a hesitation in my throttle from idle to about 800 RPM. If I'm careful to feather the accelerator, I can get by from a standing stop. It's a bit difficult when going into overdrive without a lurch though. Once I'm past that point the car really goes, nice and smooth too. The fuel pressure is good and so is the vacuum advance. I recently rebuilt the carb (needle, seat, gaskets and acc. pump) hoping to get rid of the problem but it didn't help.

I really think it's the acc. pump but the new one didn't make any difference. Could the first 1/8" or so of the carb casting be worn to the point where the leather piston no longer seals? The carb probably has a 100K on it. Could it be the check ball at the bottom of the pump?

Any ideas would be appreciated.

Thanks guys,
Pete

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