Engine will not turn.

Gmcrider

New member
Jun 4, 2020
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Champlin, Mn
Hi everybody. I'm a new member and proud owner of a 1975. I have done lots of work on the gmc over the last 6 years, one ton front end, six wheel disk brakes, headers with stainless exhaust, full paint job, all myself. But I'm not good with electrical. Here's my problem. She has always started like a champ until about to hours ago after I fill the tank will gas at a local station. And now turn the key and the starter will not engage. Battery is good and everything else is fine. The generator light is on but that has been on for a couple years and it has started fine. My guess is starter silinoid to look at first? All help is appreciated. I'm writing this as I wait for aaa to arive.
 

JSanford

Active member
Oct 4, 2019
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Sacramento, CA
Did you try wiggling the transmission selector, or putting it in Neutral? The neutral safety switch can get out of alignment sometimes.
 

Gmcrider

New member
Jun 4, 2020
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41
Champlin, Mn
I did go through the gears putting it in neutral to pull it back 50 ft so I had a safe place to look at it. I then tightened the positive cable on the starting solenoid, which know was getting power as it sparked as I accidentally hit the block with my wrench. I tried to start it and same thing no go. I then went into the gas station bought a six pack of beer and sat to think. After 2 hours of sitting and no tow truck showing up yet I turned the key again and the SOB fired right up! I drove it home and will dig into it this weekend. I will look into the neutral safety switch and make sure it is all good. Any other ideas? Thank you.
 
Last edited:

RF_Burns

Member
Oct 3, 2019
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Ontario Canada
A couple of things I would check... of course if it now will start again you can't troubleshoot something that is working.

-When it would not start, did to hear a loud click when you turned the key to start? The starter solenoid does make a pronounced bang as the contacts pull in and it pushes out the starter gear into the flywheel.
-If you heard the solenoid then either the solenoid contacts to the starter are burned and giving an intermittent connection. Check this with a voltmeter or test light on the output connections to the starter.
- Or the starter motor has an open or intermittent winding.

-If you did not hear the solenoid click, then check for power at the solenoid key terminal (#12 Purple wire I believe) If you have power when the key is turned, you have an open solenoid coil, replace the solenoid.

-If you have no power on the purple wire, then check the Neutral Safety Switch at the bottom of the steering column. It could be out of alignment or the contacts worn. If you don't have power on either purple wire at the safety switch, then suspect the Ignition switch which is just above it on the steering column. It could also be out of alignment or worn.

A trick to see if you have good power to the Ignition switch is to turn ON the dome light over your head and then watch it as you turn the key to Start. If you have good power, the dome light will stay lit. If it goes out when you switch to start, you have a bad connection at the battery or in the wiring to the ignition switch. The dome lights run off the same wire as powers the Ignition switch.

Interestingly in the past 15 years most of my vehicle battery failures have been sudden without warning. In 2005 I bought 2 new trucks and a car on the same day. Four years later, all three vehicles had sudden failures of the batteries within 2 months. With the car, my wife went to a friend's place and when she came out 15 minutes later, the battery was dead. Several years later it happened to the replacement battery when she stopped at convenience store.
 

Matt Colie

Active member
Oct 25, 2019
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South East Michigan near DTW
GMCider
When you answer Bruce's questions, I bet we can help.
Just so you know, at about 120~150K, that 10MT starter will become unreliable. Take it down and either rebuild it yourself or get it done at a good shop.
Oh, and when you can, build a sigfile. It helps everybody a lot.
Matt
 

tmsnyder

Active member
Oct 7, 2019
511
105
43
Buffalo NY
I had an intermittent no-crank, it was the brushes worn out or stuck.

If you give the starter a whack or two with a rubber mallet and it cranks then it may be the brushes.

I would also second the advice to have your original starter rebuilt by a good local old fashioned starter/alternator shop. Give them the money, don't get a new/rebuilt one from an auto chain and end up trading your good starter for a POS.
 

Gmcrider

New member
Jun 4, 2020
4
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41
Champlin, Mn
Thanks so much for all your advice. It turns out it was the neutral safety switch. JSandford hit the nail on the head. The neutral safety switch was out of alignment. Not allowing power to the starter. She is back up and running. Thanks again everyone!
 
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s trout

New member
Feb 17, 2020
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1
Might be time for a started/solenoid rebuild, but I see you have headers so you might be heat soaking the starter as you said it started after waiting for the wredker. might try a heat shield if the other fixes don't work.