If it isn't one thing it is something else PLEASE HELP

[kerls72]

I have a very strange situation with my 72 c10 big block.
Truck runs great and is a blast to drive.
But I am very hesitant to drive it anywhere because sometimes it won't start.
I have full power from battery (dash lights work, headlights work and radio works) but truck doesn't turnover of make any noise.
Does the old c10's have something to do with trans not being all the way in park even though it is?
I only ask because yesterday when it would not start in driveway I put it in drive then back in park and it started.
it is so strange happened 2 times in last week and then it will turn over and start with no issue.
I dont remember what I did 2 weeks ago when it started so i can't confirm it has something to do wit transmission.
advice please
kerley

[leftybass209]

Check your neutral safety switch. It's the half circle on the bottom of the column. It's held in place by two screws and is adjustable left to right a little. That's where I'd start.

[68350]

Could be your neutral safety switch on the top of your steering column. If it doesn't register its in park, it won't crank

[Wrcampbell]

When it doesnt start? Can you wait alil and then it will start?

Either way you need start checking for loose or broke wires or connectors.
Make sure all are tight and clean. Check all grounds also!
Could be a starter solenoid or neutral safety switch. Have you tried shaking the wire harness when you have the starting issue?

Reading what you wrote makes me lean toward a possible neutral safety switch. Most gm have two wires goin to switch. unplug wire and put a jumper in them. If this seems to stop issue switch could be bad or out of adjustment!

Good Luck !!

[kerls72]

thanks anyone have a pic of the switch so I know what I am looking for

[leftybass209]

It's impossible to miss. It's the ONLY thing on the lower column shaft half circle shaped with wires plugged into it. It's on the top side (same positioning as the gearshift indicator) just before the column exits the firewall.

[Andy4639]

Here you go!

[hugger6933]

Just for testings sake, you can jump the two purple wires and see what the truck does. That will eliminate the switch or its adjustment beig off some. They have a condition that that wear where the tab[or tang depending] that comes from the switch to the shifter tube gets worn real bad making them go bad. Jim

[RustyBucket]

Yesterday I got in the Blazer at the grocery store, turned the key and NOTHING happened. I sat there a minute and cussed it good. I wiggled the key up and down while I turned it and it fired right up. It's done it a few times before and I think the switch is failing. Not sure if it starts because I wiggle the key up and down or because I cuss it so good. I don't have a neutral safety switch,.... std. trans. and it will start in gear.

[briank]

I have same problem in my 68 suburban. So far too lazy to adjust everything ,I just push the selector lever to make sure its in park when it wont turn over and it fires right up.

[WIDESIDE72]

in my 72, when I first reinstalled the column, I had to pick up on the shift lever a little while cranking it. I started to leave it as a "theft deterrent", but decided if my wife ever had to drive it, it would be best to have everything as functionally correct as possible.

I hate to admit it, but I used a 3/8 extension and a hammer to tap the switch from underneath on the left side to adjust it. ( I didn't have to wail on it, just a couple of love taps.) Those little mounting screws on the NSS are a bear to get to on an installed column

[Longhorn 70]

My truck used to do the same thing. I noticed the Ammeter would deflect when I turned the key and return to center when I let go. IF I'd tap the starter when someone else turned the key, it'd start. I replaced the wiring from the connector to the starter...that worked for a few months then it started again. Replaced the craptastic solenoid on the starter with a U.S.A. made solenoid....still works to this day! All solenoids are not created equally. The one on there is a Standard Ignition Parts piece. Also the points they had were great! Blue Streak points...

Next time it happens, see if the ammeter moves when you turn the key.

P.S. I just checked and the Standard Motor Parts solenoids are now made in Mexico....I don't know if that will affect the performance of the part. Just get a good quality solenoid. Yours could be heat soaking.

[davepl]

The purple wire that fires the solenoid. Resistance in this wire, normally from people cutting it to install an ammeter or something similar, will cause this problem.

If this is the cause, it will also be worse when hot and almost never happen on a cold start. That usually distinguishes it from the NSS (unless it's working but with marginal contacts).

If it's the same cold, ignore my post. But if its worse when hot, there you go.

You cannot measure resistance in the wire because it will be too low anyway. Really the only way to know would be to get it into a no-start situation, measure voltage present at the solenoid -during- a crank attempt, and see where you're at. Only voltage drop will tell you this, not a simple resistance test.