Lately I’ve noticed that our cars sometimes won’t start in Park, but will start up fine in Neutral. What could cause that, and should I be worried about it? FTR they are both Nissans–one is an old Infiniti G20, and the other is a 2000 Altima.
Bad safety switch. There is a switch to sense both neutral and park positions and allow the starter to engage only when these positions are selected. Depending on the design, it could be one switch with two positions, one of which is bad; or two separate switches possibly with a loose connection, or a bad contact. In any case, you should be fine until you can get the car in to have the switch replaced.
Q.E.D. is probably dead on right, but I wanted to mention there is an outside shot that it is flywheel related. The starter won’t mesh with the flywheel. A hard click would be heard when starting in park, but the engine wouldn’t crank.
One other possibility is the adjustment of the shift linkage to the transmission. If worn, it may not be driving the switch actuator far enough to ‘make’ in park.
Exact same thing happened to an old corolla of mine.
'twas the safety switch.
The first time I replaced it, until I realized that it could be adjusted when I was putting the new one in.