Car won't start until you tow it to the mechanic

2000 Chrysler 300M won’t start until you tow it to the mechanic. The moment it is off the hook at the mechanic the car immediately turns over. Minutes before going on the hook, nothing. This has happened twice. Battery and starter have been replaced and connections double checked. Any help or suggestions are appreciated.

Gary, About That "The moment it is off the hook at the mechanic the car immediately turns over.

By “turns over” do you mean the engine starts ?

Some folks say “turns over” and they mean it starts running. Others use the term “turns over” to mean that the engine cranks over, but doesn’t necessarily run.

When it’s not starting (before towing) and you’re turning the key does it do nothing, cranks over, or make a clicking noise ? What does it do/not do ?

CSA

I’ve seen similar on other Chrysler products. The one that drove me crazy was a Plymouth Breeze. The primary cable connected to the main panel box before connecting to the starter. A corroded connection right at the panel box was causing all the trouble.

@common sense answer: Thank you for your response. I should have been more clear. The car does start once off of the hook(and 20 successive times since). Before going on the hook not even one click. Tried to jump it and got one click. Again starter and battery replaced.

Sure it will fail again at the worst possible time if we don’t get to the root.

Thanks again for your thoughts.

@BustedKnuckles Thank you for your reply. I am going to have my mechanic check for that main panel box connection immediately. Sounds like it could be a Chrysler design flaw.

With no starter motor operation or click sound I would suspect a faulty neutral safety switch. Chrysler may or may not refer to them as range selector switches.

That’s the switch that allows an engine to start in park or neutral only and failure of this part on many makes of cars is not that rare.
Next time it acts up try shifting into neutral or wiggling the shift lever around. If it fires up then the switch is probably the cause.

The first thing to check is the voltage at both starter terminal connections during attempted cranking. Both wires should remain connected when you do this. If the voltage at both is above 10.5 volts during attempted cranking, and the starter motor doesn’t turn on and crank the engine, it is probably a defective starter motor (or the connector). Measure the voltages between the terminal and the starter case.

There’s some slight possiblity the engine is locked up for some reason and isn’t being allowed to turn also. This could be proved/disproved by manually turning the crankshaft pulley to make sure the engine is free to turn.

I expect you’ll find that the big thick wire to the starter motor’s voltage is ok, but the thin wire isn’t being energized (it will read zero volts instead of above 10.5 volts). In that case, something upstream is the cause. The starter motor won’t turn on if it doesn’t receive the start signal on this thin wire. Could be the ignition key, neutral start switch, or often there are relays in the ciruit which sometimes fail.

This problem turned out to be the range selector switch/neutral start switch. Thank you again to all that replied. This is an outstanding forum with quality commenters.

Great! glad you got it resolved. Thanks for coming back and letting us know what the problem was. It may help out someone with a similar problem.

We Have A Winner !

Congratulations And Hats Off To OK4450 ! Awesome.

CSA