I had the exact same problem,i managed to get the spray once into time, but the second time the light bulb didnt go green.But the solution is quite simple,
1) just remove the cleanser spray form the delorean.
2) click on the delorean, and watch the lightbulb is green
3) now put in the cleanser and continue the story..
if you put in the cleanser spray BEFORE you looked into the delorean you wont see a green light bulb. try it.