starting problems

[synical]

hey guys, been having some starting problems lately. trying to figure out exactly wat the problem is and wat i should do. heres the story:

car has been sitting for about 3 months without starting. tried to start and didnt. so changed with a brand new battery and it would start sometimes. thought it was the starter motor, so got a replacement. car has been starting a little more often, but still wont start on the first turn of the key. trying to crank the engine, get a voltage of 5v, which isnt normal. battery voltage at ignition is about 12v. battery voltage while engine running is 14.2v. the only time it will start is when it wont start the first 3-4 times, then i just click it into high beam and wait till i see the headlights are brighter so i know theres enough charge to start the car. head unit is also turning on and off until i got enough charge to start the car.

any help is appreciated, and i do apologise about the long post.

 

[danny1987]

sounds like something is drawing curient get a clamp meter on the battury lead make sure everthing is off see what the reading is shouldnt be really high maybe a couple of amps for the ecu etc if more something is flating your batt. or else you have a faulty batt.

 

[synical]

is there a way to find out exactly on how to isolate the circuit?

 

[Chirpstr]

for the flashing, head unit earth might be making bad contact...

 

[Chirpstr]

has it been a bit better when you got the replacement starter motor? was it new?

 

[synical]

with the head unit, it would flash till i get enough power in the car. then it'll stop.
and yeh it has been a little better with the starter motor. its not new though, got it from the wreckers. (which may have been a bad thing)

 

[Chirpstr]

maybe you got the wiring mixed up with head unit...yeah check starter out try and get a reading from it when your turning it over...wreckers can be good in some ways but they can be dodgey aswell...

 

[synical]

im 100% sure that i got the wiring correct for my headunit. wat is the voltage of the starter motor when cranking the engine?

 

[commsirac]

If you are getting 5V across the battery when you activate the starter, either:
1. battery is in need of replacement, but youve already been there
2. there is a massive short happening somewhere when you crank the starter.
3. there is something stopping the motor from turning, do you hear anything happening at the starter......humming, clicking etc

In a healthy system, the voltage when cranking the starter should be ~10.5V.

It would be unlikely that your massive short is happening on anything inside the vehicle as there are no wires that could handle that sort of current going through the firewall.
I would be suspecting a short in the starting circuit/relay

 

[synical]

with ignition on, dont hear a thing from a starter. one of my friends think that the starter motor is sticking and suggests that i hit it with something to unstick it.
in regards to the starter circuit, i would need to look into that, and the relay has been replaced as well. would the starter circuit only consist of the negative and positive that sits on the solenoid?? i even changed my battery terminals with no luck.