Was driving thru Las Vegas today and the old girl decided to not start after 4 hours of highway cruising.

Always start fine cold. However, it started doing that a day ago, turn the key, lights all on, click and nothing. I would do it several times and disconnect the battery, bam it would start. But when it does start hot it would die down just a little before it runs normally.

But today it didn't, I waited an hour and went back to try still nothing. I thought it was the neutral safety switch? Do they even have those for 1989 740? I mean one time it started in reverse... but I still wiggled the shifter around PRND21, no result. Eventually, a kind samaritan helped me jump-start it and it started. The battery is a year old (have been disconnected and sitting for 6 months tho)

I will test the voltage tomorrow but I am just curious, how can I make sure this is a battery problem or a starter problem, as I am not in a position to change everything lol (I say that but I have already done soooo much work on this car, heater core, drivetrain, etc)

thx for your help~