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Old 10-19-2012, 04:03 AM
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Why does it die when I apply brakes?

my 74 El Camino- stock 350/TH350 (not TH350C) has been running tip top. All of a sudden it dies when I apply the brake during idle- like at a stoplight.

I thought vacuum leak: Disconnected the brake booster hose at the intake and plugged the intake there... same deal!?

Anything else I can look at?

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Old 10-19-2012, 04:51 AM
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Your first troubleshooting sounds reasonable, so I'm surprised you did not find a bad brake booster that was screwing up the vacuum.

However, if its not vacuum, then maybe its electrical. Something may be grounding out when you press the pedal, or a sudden electrical load may be causing such a draw on the alternator that it pulls the idle down very quickly and it dies.

- Hold the brake pedal down and start the car. Try this in several positions of the pedal travel. What you are looking for is a point where something grounds out and causes an electrical problem. If you have an aftermarket tach, take a close look at the wiring to the HEI to make sure you don't have a wire running next to the brake pedal arm that is grounding out the ignition.

- Try pulling the fuse for the brake lights to see if it resolves the problem. I don't think the lights could put enough load on the alternator to pull the idle down significantly, but maybe something else (add-on 3rd brake light?) is drawing excessive power. Check for any relays that might be connected to the brake light circuit. If someone has added any aftermarket security devices, that would also be a good place to start.

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Old 10-19-2012, 07:05 AM

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look for a pinched wire under dash thats getting pinched when your on the brake..

or a loose ign switch on the column at the base..
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Old 10-19-2012, 11:05 AM
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Does it sputter some times or go off like a switch. Could be low fuel level in the float bowls. was a common issue back in the day. You would slam on the breaks or break for a few seconds and the motor would sputter right out. Could aslo be same problem in reverse with too much fuel.

Hope this helps.
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Old 10-19-2012, 01:41 PM
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Got cruise on it?

When you touch the brake, cruise will come off normally. If switch is screwed, it could kill the engine by backfeeding to ground.

Also, check the electric solenoid that sets up the carb idle, when ignition is turned on the solenoid will pull the linkage and add a couple hundred rpms to start engine and when turning the engine off, it will disengage solenoid and linkage to avoid run-on of engine. Engaging A/C also adds rpm.

Last edited by alittle1; 10-19-2012 at 01:51 PM.
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Old 10-20-2012, 02:42 PM
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I am certain that the condition exists even when the brake booster is taken off-line. I will search under the dash to have a look at the brake pedal switch. I am not certain that the switch could be the cause of the problem- not sure where or how the switch could cause a ground strong enough to kill the engine... any other ideas are welcomed.

Thanks in advance.
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