Truck stalls when you push on brakes

Tiny
JIM LEAVITT
  • MEMBER
  • 1994 DODGE RAM
  • 5.9L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
Truck stalls when bake pedal is pushed, in any gear, even park. Disconnected vacuum line to brake buster, still stalls. Plug vacuum line, and stalls. Will run with vacuum line unplugged, but still stalls when brakes are pushed.
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Wednesday, November 30th, 2016 AT 12:18 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
Was the battery recently disconnected or run dead? Will the engine stay running if you hold the accelerator pedal down 1/4"? If it will not, unplug the brake light switch under the dash, If the stalling no longer occurs, the problem is likely related to the current the brake lights are drawing and a good place to start is with a charging system test. You can start that yourself with an inexpensive digital voltmeter. Measure the battery voltage with the engine running. You should find between 13.75 and 14.75 volts. If it is low, we'll need to check further for the cause. If it is okay, that only means it is okay to perform the second half of the test. That is "full-load output current" and "ripple" voltage. A professional load tester is needed for that.

If the charging system can't keep up with the little current brake lights draw, it won't keep up with the higher current the heater fan draws, and running that should also lead to stalling. Making these observations will tell us if there is an electrical problem or a vacuum-related problem.

Also observe if you get a nice strong "idle flare-up" to 1500 rpm for a couple of seconds when you start the engine.
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Wednesday, November 30th, 2016 AT 5:09 PM
Tiny
JIM LEAVITT
  • MEMBER
Get 14.3 volts with engine running. Heater seems to have no effect. Stalls with or without heater on. In idle engine runs between 600-800 rpm's. Get idle up to 2000 rpm's on start up. Disconnected trailer plug. Seems to have helped a little. Still stalls, now lights are all messed up.
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Thursday, December 1st, 2016 AT 8:44 AM
Tiny
CARADIODOC
  • EXPERT
What does "messed up" mean? What are the symptoms, and can I assume you mean on the truck, not the trailer?
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Friday, December 2nd, 2016 AT 9:22 PM

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