Electrical problems

Tiny
FIREBIRDFAN87
  • MEMBER
  • 1991 PONTIAC FIREBIRD
  • 3.1L
  • V6
  • RWD
  • AUTOMATIC
  • 138,961 MILES
I cannot check my engine codes by paper clipping a and b on the all or obd, before it worked fine, the motor fan would kick on and it would show codes, now it does nothing. Also my fuel pump is not turning on when I turn the key, I just installed a new tank sending unit and pump recently. I could use some help!
Saturday, June 11th, 2016 AT 12:10 PM

3 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
If the battery is down, we are just spinning our wheels, trying to test anything. I have seen older vehicles where the mil no longer worked. If that is the case, you cannot check codes. When the mil would not work for whatever reason, I used a scanner that showed live engine data, plugged it into the data-link connector, it worked fine on that vehicle, so I did not think the computer was the problem. You might turn on the key, battery has a full charge, correct. Then check any sensor that uses a ref voltage, If no ref voltage have to start testing at computer, voltage and grounds.

The computer sends voltage to control side of fuel pump relay for initial prime, key on engine off, no rpm needed unless cranking.
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Saturday, June 11th, 2016 AT 12:52 PM
Tiny
FIREBIRDFAN87
  • MEMBER
  • 2 POSTS
I have a multi-meter, but I am not sure how to use it, where should I start with checking for the correct voltages? I will be home after eight o'clock tonight so I cannot do anything with it until then, but thanks for the information so far!
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Saturday, June 11th, 2016 AT 1:05 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Read through this article it give you an idea on how to use a voltmeter, we are going to be making a better guide soon but this will get you started.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

check the battery with this test,

https://www.2carpros.com/articles/how-to-check-a-car-battery

Let us know how it goes

Best, Ken

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Tuesday, June 14th, 2016 AT 7:46 AM

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