Neutral safety switch or something else?

[Bob67Barracuda]

For several years my 1967 Barracuda will occasionally do nothing with key crank. This car has ‘71 340 and 904 auto 3-speed from the early ‘70s. Problem was happening even before the 340 went in a few years ago. When it happens, headlights work and it’s not the battery. No crank in neutral or other gears. Didn’t take long to figure out that if I jiggle the floor shifter while it’s in park it will more often than not fire right up. Sometimes I’ve had to open the door and push the car a bit with my foot while jiggling the shifter. It’s never been more than a minor inconvenience and never left me stranded. Usually I can hear the click when I know the shifter has seated properly and/or triggered the switch. Today in the garage it was worse. I had to really shake the car to get it cranking. After that went for a drive with multiple shut offs and it was fine. I find that if I shift into park as I’m still barely rolling it’s less prone to happen.

I always figured there was a switch in the floor console but apparently not.

After reading a bunch of previous threads, I’m thinking NSS switch. But could it be the shift linkage? That’s where I’d be fuzzy on how to realign or even know what to look for.

Any input greatly appreciated!

 

[4spdragtop]

67 here as well. Yep switch or loose linkage. Console shift? I've never had to push/rock car thankfully.

 

[67Dart273]

Here is how this works. Locate the start relay. I believe yours should be on the fender apron behind the firewall. The large stud/ nut is a junction as well as 1/2 the set of contacts. The big "square" terminal goes down to the starter solenoid. The two small "push on" flag terminals are the relay coil. The yellow one is the 12V "start" signal from the key switch. the remaining wire goes down to the neutral switch on the transmission.

With the shifter in P or N, the neutral switch is grounded and so that grounds the coil in the relay. This allows the relay to activate when the key is twisted, as the yellow will feed 12V to the coil. The contacts in the relay close, the "big stud" is direct to the battery, and that will power the solenoid wire leading down to the starter.

You are fighting an intermittent, so it might take some time. The neutrals switch must be grounded (in N or P) to allow the relay to fire. Could be a problem there, loose, corroded wire connection, bad switch, or out of adjustment linkage.

Same with the yellow coming from the key switch. bad connection, or even a bad ignition switch.

The relay itself could be bad/ intermittent. AND the wire from the relay down to the solenoid could be intermittent, or the starter / starter solenoid

This is going to take time, because it is "sometimes." What I'd do............

CAUTION: Bear in mind that some tests will negate the safety of the neutral start switch, so make SURE the transmission is in N or P before doing so!!!

1....I'd wire a temporary push button between the big stud and the square terminal, route into the car and even if you just tape it up "safe" and let it hang, next time the key won't work, try the push button and see if it cranks. If so, try the key again to make sure.

If the push button works but the key does not, you have eliminated the starter.

2...Next time it fails, have an alligator clip jumper wire. Disconnect the small flag terminal that is NOT the yellow, and clip to the relay terminal and to ground. THIS WILL BYPASS the neutral switch. Now see if it cranks, using the key. If so, the trouble is in the wire to the neutral switch, the switch itself, or something is wrong or mis-adjusted with the linkage.

3....If the above test, with the jumper lead connected does NOT crank, try leaving the jumper connected, take a second one, and clip to the big stud on the relay. BE CAREFUL this is DIRECT to BATTERY.. making sure the trans is in P or N, take the jumper and jumper to the terminal on the relay connected to the yellow "start" wire. If it does not crank, likely is a bad relay.

THIS IS A SIMPLE CIRCUIT but an intermittent can complicate and frustrate.

 

[grjammer]

Playing with the shifter and rolling the car to make it start indicates a bad NSS on the trans or the linkage requires adjustment. As you can hear it click and then it starts, I would set the linkage according to the manual. it's a single bolt on a rod going from the torque shaft arm to the gear selector arm on the transmission.

 

[Bob67Barracuda]

Thanks, everyone! Great info to tackle this.

 

[moparlvr166]

One thing I have seen many times is the ground strap from back of Cyl head to fire wall is missing, loose or bad contact causing this problem, very simple repair and if it still acting up now you know what it's not and continue on with diagnosis.

 

[Dana67Dart]

Check the NSS on the trans to be sure it is snug. Also check for oil in and around the terminal.

I have heard of people slightly tightening the NSS and its function coming back

If it has not been changed it should only have 1 post for the NSS wire that leads up to the Starter relay. 67Dart273 has great trouble shooting advice for you

I always figured there was a switch in the floor console but apparently not.

there is a switch in the floor console but it is for backup lights only