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Hooked up the battery backwards now it will not start

Tiny
MARY MAHER W
  • MEMBER
  • 1995 TOYOTA 4RUNNER
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
Had hooked up the battery backwards now it will not start. Trying to get spark while checking coil wires, I have two going to the coil on one plug one wire is hot and the other has no power. When I hook up the plug to the coil both become hot as I see it on the manual one is positive and the other is negative. Do I have a bad coil?
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Monday, March 13th, 2017 AT 7:54 AM

3 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Hooking the battery backwards would often result in blown fuses. Check them all, some are underdash.
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Monday, March 13th, 2017 AT 8:42 AM
Tiny
MARY MAHER W
  • MEMBER
  • 2 POSTS
Checked and replaced bad ones replaced computer, and ignition igniter, have power going to coil and igniter no power going to mass air flow sensor. Still no spark that is why I am at the coil. I am not sure if both sides should be hot when I connect the plug to the coil?
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Monday, March 13th, 2017 AT 10:00 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,935 POSTS
Hi Mary,

There is a EFI relay and a circuit opening relay that could have burned out when the battery was connected backwards, here is a wiring diagram and a guide so you can do some testing.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please run some tests and get back to us so we can continue helping you.

Best, Ken
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Monday, March 13th, 2017 AT 11:15 AM

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