Hard to start

i’m having a hard time starting my 2000 chevy impala. it orginal had a security plug on it. i had it removed. to start when i turn on the turn signal there was a noise, the odometer when blank, the air bag symbol appeared. the next time i tried to start the car it would do the same thing but wouldn’t even turn over. sometimes you can turn the key on and wait 30 seconds, step on the brake and it may start. i have continued to try for up to 3 minutes. if you put on jumper cables sometime it will start. what is the problem? drmarty

No noises at all when you start it? If you turn the dome light on and start it, does the dome light dim at all?
If it dims, clean the battery terminals.
If not, I’d check the connections to the starter or the inhibitor switch that’s attached your your shifter. Maybe move it to N to see what happens.

Stepping the brake makes a difference? If you have an automatic, the brake is probably part of the transmission shift safety mechanism. Makes it difficult for a child to shift the car to D when it is in P. So maybe this has somethng to do with the transmission safety interlock. Have you tried starting in N instead of P? Wiggling the transmission shifter a bit, to and fro?

If that doesn’t work, to get to the bottom of this problem straight-away, ask your mechanic to measure the voltage on both terminals of the starter motor during attempted cranking. Both should be 10-10.5 volts (or above) during attempted cranking. If either is significally less than 10 volts, the problem in in the electrical system. If both are well above 10 volts, the problem is most likely the starter motor, usually the selenoid contacts.