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Truck dies out when step on brake

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Old 10-02-2009, 09:14 PM
Brock_Samson Brock_Samson is offline
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Thumbs down Truck dies out when step on brake

My '68 F250 Camp-Sp. dies out when I step on the brake.
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Old 10-03-2009, 04:07 AM
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could be that the idle is low to begin with.
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Old 10-03-2009, 07:21 AM
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Check your carb float level. If float is set too high, you can get fuel slosh out the vent tube and it goes down the carb and floods the engine. At least that can happen on a Holley, not sure about Ford carbs.

Another possibility is if you have a dashpot to slow the carb return to idle rate down, it could be shot. Try it in the driveway. Momentarily open the throttle by hand with the engine running, and then let it go. It should return to almost idle quickly, then slow down and the proper idle will come on slowly.
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Old 10-03-2009, 10:20 PM
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Dash Pot shot ? If it has one the diaphragm may have gone to greener pastures letting the throttle arm slam closed rather than easing to it's seat.

http://www.allfordmustangs.com/forum...lp-dashpot.jpg


Whoopser! I see Argess covered that already.
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Old 10-03-2009, 10:28 PM
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Do you have power brakes? If you do you could have a bad diaphragm in it. Then your float setting could be too high too.
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Old 10-03-2009, 10:28 PM
Brock_Samson Brock_Samson is offline
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Quote:
Originally Posted by Argess View Post
Check your carb float level. If float is set too high, you can get fuel slosh out the vent tube and it goes down the carb and floods the engine. At least that can happen on a Holley, not sure about Ford carbs.

Another possibility is if you have a dashpot to slow the carb return to idle rate down, it could be shot. Try it in the driveway. Momentarily open the throttle by hand with the engine running, and then let it go. It should return to almost idle quickly, then slow down and the proper idle will come on slowly.
The carb is brand new, holly 2300. its strait bolt up out of the box.
Could it be the brake booster?
the booster looks like its the OEM same with the master cylinder.
it seems like the motor looses vacuum when i step on the brake also.
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Old 10-13-2009, 02:09 AM
deejaytee deejaytee is offline
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I had that issue on my 73 F-250. When the brake boost went out the engine would run badly and die. I also had a terrible time trying to stop it. Are you having any braking issues? If you are replace both the master cylinder and brake boost at the same time. They usually go out relative close to one another.
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Old 10-13-2009, 03:24 AM
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Don't replace that booster just yet...there may be nothing wrong with it.

1968/72 F100/250 power boosters have a replaceable vacuum check valve. This valve fits into the booster using a rubber grommet.

What happens: The rubber grommet hardens up, then cracks apart...now you have a vacuum leak.

The valve may have failed as well.

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MSRP: $10.67 // FTE sponsor Y2KFORDPARTS.COM price: $5.76.
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C9AZ2B176A .. Check Valve Rubber Grommet / Obsolete

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GREEN SALES CO. in Cincinnati OH has THREE = 800-543-4959.
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