1990 ls400 no crank

[@pdxslideways33]

Hi guys I'm new here. I've been having problems with my ls400 for about five months now. The car will not crank over at all, all of the lights and fuses come on and click in but as soon as I turn the key to crank the car all the lights go off and I here a clicking comjng from ecu I've replaced that and still doing the same thing and I've tried 2 brand-new batteries any help I'm close to giving up on the car I love

 

[gloverman]

Have you done any testing of the starter circuit?

 

[ivan129]

Should be an easy fix.
You should hear the solenoid on the starter motor click when the ignition keys is turned to start? sign the starter is being powered, no click, blown fuse starter relay or starter motor.
Are the battery terminals, +ve and earth cables clean and not corroded at connections. ensure now resistive connections, ie voltage drops
Can you turn over the engine by hand (use a long bar on the harmonic balance bolt) sign the engine isn't seized
Put a multi-meter across the battery terminals, should read about 12 - 12.5V for a good SLA, when you turn the key to start the voltage should not drop below 11V. Tells you the battery is ok.