commander_47

I have run across a very very weird problem in my opinion.

My car (74 LS4, 454, with TH 400 trans) developed a dangerous condition that has me perplexed.

If the ignition is on, not running, but just to on, and you move the shift lever into Reverse, Neutral or drive, the CAR WILL START!!!

If the car is already running, and I shift to reverse, the starter will engage, but will shut off if I jiggle the shifter.

At first I suspected the neutral safety switch, but I just replaced it last year. Could it be defective?

In my experience the opposite is normally true if the NSS is inop, the car won't start.

Any ideas?

carriljc

Take some continuity readings with the NSS installed. Should only read in Park and Neutral. If it's iffy, then I'd remove the NSS, clean it, put some dielectric grease in there, and reinstall it...ensuring that it installed appropriately.
Worth a shot anyway

Mdbirk

Ever see that movie Christine? I'd be careful, it might be haunted.... just saying.

vbgod1

Might also check the ignition switch. There should be no power signal to the starter unless the key is turned to start. Yes, the safety switch should prevent starting unless you are in neutral or park, but there should be no signal to start unless the key is turned that far.

C

Peterbuilt

Try adjusting the NSS switch.


Still not working:

Maymyvetteliveforevr

I'm having as similar problem (75, TH400) in that I needed to replace my NSS due to a seat belt light issue. Now when I shift into drive my starter engages, but will disengage once I'm actually in drive (in other words, jiggle the shifter).. Now the started won't engage at all (no clicking sound, full battery charge). It's still in storage, therefore I'd like to subscribe to your post and see how you trouble shoot and fix the problem.

My issue started with the NSS, not sure if that's a coincident.

Good Luck.

commander_47

Wow, great information, especially Peterbilt.

An update:

a. I took apart the console and got to the shifter and NSS.

b. Removed and took apart the NSS. I immediately noticed a little spring mashed and flat against the contacts. I wish had taken a picture but didn't think of it at the time. This switch is kind of complicated. If you look at it from the outside, you see where the 5 wires connect. Inside, there are bars of brass that run along for various lengths of the wires. The slider part, has three barrel tubes of brass in slots that make contact between the stationary contacts when it moves. There is a little spring under each barrel tube to keep pressure on the contacts. I have no idea where the fourth mashed spring came from.

c. Lubed and replaced the switch and ran tests. Now I have a weirder problem. All works well except for neutral. back up lights, seatbelt interface, everything. In park neither Purple, or the Purple with white stripe is energized until I turn the key to start. After letting go of the key the engine runs and idles fine, no power to either purple wire.

d. Put it in reverse, reverse lights come on, engine shifts to reverse, all is fine.

e. Put it in neutral now, and most of the time, nothing happens, except you can't start the car in neutral. In other words, shut the car off in neutral. Then try to crank it, and it won't crank at all. I have constant power to the PURPLE wire from the starter, but nothing coming from the ignition switch on.

f. On a few occasions after the clean up, the car starter would engage when put in neutral, but way way less than before.

Any ideas why the starter would send 12v to the NSS, and the ignition switch doesn't? But only in neutral. If I shut the car off in neutral, then the purple wire is not hot. If I turn on the key and try to start to in neutral, power shows up on the purple wire but not the Purple WWS. If I put it in park, then all works normally.

I'm suspecting a bad switch. Mainly because it seems to me if there was an issue with the ignition it wouldn't work in Park. I can help but think one of those barrels is misaligned somehow in the switch.

Dang switch cost nearly $100 and I just put this one in last year.

Buccaneer

It sounds like your NSS is not adjusted correctly, but it could also be bad as well. Get your meter out and do some checking. It should ONLY work in Park and Neutral, no other gear should the motor start. What ever you do, DO NOT use dielectric grease on it. Dielectric grease IS an insulator, not for conductivity. You will degrade the conductivity of the switch by doing that. Dielectric grease is for things like your spark boots to make them come off easier. I hope this and what has already been presented helps you out. GL

commander_47

Well, the problem appears to be fixed. I was able to get a new switch at Summit today. With my discount and Summit Bucks it was only 71.00 including tax. Not too bad considering what I paid for the first one.

I am attaching some pics for all to see as I went ahead and took the bad one apart again.

The first one shows the switch split apart. You can see the three barrel pins and springs.

The second one shows how those pins and springs go in. There are three little recesses the springs fit in, and the barrel pins lay on top. On the bottom of the pic two, you can see an additional spring. One of them was mashed and shorting across the barrel pins somehow. The other spring just fell out when I took it apart. I have absolutely no idea what they do.

Third picture simply shows you the rails the barrel pins arc across, and also the four pins you bend out to take the switch apart.

Pic Four is the replacement I bought.

Pic five is simply what it looks like sitting in the car. The switch is aligned and working, I will test and finish the job tomorrow.