Starter motor not engaging unless battery booster is connected. (NEW Battery)

[NSX_NA1]

Hi...

I know there are several threads about starting issues.

I've tried most of the suggestions but because my issue is a little unique i thought it is worth creating a new thread.]

I have tried different batteries including a battery that is brand new 60amp and 550cca.

The fuel pump primes and the car clicks, sounds like it's coming from the starter motor.

Connect a battery booster in jump mode and it fires no problem.


What i've tried:

• removed the 3 main earths and cleaned contact points both ends. (behind battery, gearbox and rear bulk head.)
• Swapped main relay with a spare, it's not new but i don't have any reason to believe it not to be working.
• Replaced the Ignition fuses as suggesting in another recent post.
• Cleaned battery terminals.
• Cleaned Alternator earth.

Next steps:

• check the ignition switch, clean the terminals but i'm doubtful as it does start, but only with a booster.
• I'm going to remove the starter motor terminals and clean them, am i correct in thinking there is only 2? one from the harness and another from the solnoid? There doesn't appear to be a earth for the starter unless i am mistaken?

What else can i check?

The reason why i believe my issue to be different is mostly because it does start when i connect a booster which raises the Volts on the dash.

Thanks.