1979 mb 300cd

I recently acquired my parents 1979 Mercedes-Benz 300CD, which was sitting in my parents’ garage for at least 3 years. My husband and I are trying to restore it to a good drivable condition. However, the same issue keep plaguing us. Sometimes when we attempt to turn the car on, it won’t start. My husband and uncle don’t believe it’s the starter and we recently replaced the alternator and battery. The weird thing is that when I put the car in neutral, it will start up. My husband thinks it might be an electrical issue or loose wire. Any advice would be great. I love this car and can’t wait to start driving it again.

The neutral safety switch (NSS) is bad or mis-adjusted. This switch prevents the starter from working unless the shifter is in ‘Park’ or ‘Neutral’. You’ll need a manual to get this car restored right, and it will have instructions to adjust the NSS if adjustable. If this doesn’t fix it, replace it.