2004 acura tsx cranks but start sometimes or not at all. have seen a green key light stay on ( not flashing) on dash. read that usually is fuel pump relay. bought one . before putting it in took battery to get tested. had to small of a battery (500 cca/400 of which it was only at 374 amps) when it calls for a 625cca/500. put a slight bigger battery 650cca/500 in it left old fuel pump relay in but put new fuel pump relay in main relay slot car started right up. turned off , WONT START AGAIN.

 

The problem could be more than a fuel pump relay requiring proper diagnostics and not arm chair guessing and throwing parts at it. If you don't have a proper fuel pressure tester and other diagnostic equipment, suggest you do your best to get vehicle to dealer for diagnostics.

 

your in the wrong forum id mov this elsewhere

 

The green key light means there's an issue with the immobilizer. It should go off when you're in the on position. It should only come on for a second or 2 before going off.
if the key light is lit then it's not going to start because it's not recognizing the key. You shld be diagnosing the immobilizer rather than starting system.