Power (sometimes!) shuts off starting car! (2000 Ford Mustang) - please help!

repair
mustang

#1

My car sometimes shuts off when I attempt to start the car. I start the car, hear a loud click and the electricity to the entire car dies. No dome lights, no headlights, no radio.

I disconnect the negative terminal and re-connect and all power comes back.

The weird part is, sometimes it DOES start. Sometimes it starts on the first try, sometimes I have to disconnect/re-connect 9 or 10 times before it’ll eventually start. Once it starts it never loses power or has any issues.

What could it possibly be?!

I’ve ruled out the battery, as it’s literally brand new. The connections to the battery terminals seem VERY secure (I’ve re-done them a few times) and there’s no corrosion at all. I sandpapered to be sure. I’ve also ruled out the fuel pump (obviously).

Could an aftermarket alarm system inherited from a previous owner be doing this? Could there be an issue with the starter? A connection issue elsewhere? Is there any way I can track down the issue on my own? Any help would be appreciated. I’ve been trying to save money by working on my own car - if it’s too advanced a job I don’t mind taking it to a garage, but I’d like to at least figure out the issue so I don’t get ripped off!

Thanks in advance!

-Max


#2

The cables to the battery may be so corroded under the insulation that you cannot see the problem. This is common for a car this old.
Another place to check for a clean connection, is the connections on the far end of those cables.

BTW even a new battery can be bad.

Yosemite


#3

Check both the ground connection to the motor or chassis and the connection to the stud on the starter motor. Also look at the cables for any signs of corrosion at the termination points, or swelling indicating internal corrosion.


#4

This might require an experienced mechanic to solve, since there are a lot of things it could be. When you start the engine, a lot of current is needed all at once to go from the battery to the starter. One idea is that this current is heating some connection up, and the thermal effects on the metal in the wire or connector somewhere is causing a connection to open up in the wiring harness. It may be that simply waiting for it to cool down is all that is needed, and disconnecting the battery isn’t having any effect. That’s why sometimes disconnecting the battery once works, and other times it takes 9 times.

The fact that you have no headlights, dome lights, or radio is actually a good thing, as it will make it easier for the mechanic to figure out where the problem circuit is.

Here’s some possibilities where to look. Often the best way to rule them out one by one is to temporarily replace the part with a known good one.

  • Main circuit breaker, if applicable to your car
  • Broken an defective fuses can do this
  • Batteries will sometimes fail this way
  • The entire circuit path for which the starter motor gets its main battery power
  • The ignition switch
  • Various relays associated with the “start” function