Starter switch wiring

[Sinfulsaint24]

just bought a 69. It was supposed to start and run. It doesn't turn over and it isn't the battery. The guy said it had a new harness on it and, well, look at the back of the ignition. I've gotten it to crank and start once, and used the clutch the other time. However, the key won't turn it off. Any help?

[Andy4639]

Time to start chasing wires!

[ray_mcavoy]

Welcome!

I'd recommend using a 12V test light or multimeter (set to DC Volts) to check for power on the various wires. And check to make sure they're connected to the correct terminals on the switch.

The red wire is a power feed to the ignition switch. It should be connected to the "BAT" terminal and be live all the time.

The purple wire is used to energize the starter solenoid. It should be connected to the "SOL" terminal and only have power with the key in the "start" position. Since your truck has a manual transmission, there won't be a neutral safety switch inline with that purple wire like there would be with an automatic. And these years didn't use a clutch safety switch either.

The pink wire feeds the ignition. It should be connected to the "IGN" terminal and have power with the key in both the "run" and "start" positions.

So if the wires are connected correctly and you don't have power on the purple wire in "start" and/or the pink wire remains powered even with the key off, you are probably looking at a bad ignition switch.

[VetteVet]

Well this one should be fun.

Given that you don't know much about the truck's history, we'll have to sort it out as we go along. The one thing we have to have you do first and most importantly is to work safely. I'm sure you are aware that the truck will start in gear if it's a standard shift.I would like you to be certain it's out of gear and the rear wheels are blocked up off the ground before you start troubleshooting .You can also pull the coil wire if it has the points distributor,or the Bat wire if it's been converted to an HEI distributor.

Does it have the original alternator and external regulator or has it been converted to the internally regulated alternator?

Do you have the idiot light dash cluster. or the gauge cluster?

Now you realize that the starter circuits are different between the wiring harnesses, depending on whether the vehicle is a standard shift or an automatic. The standard harness does not have the neutral safety switch wiring, and has no feature to keep the starter from turning if the vehicle is in gear. The later years had a clutch safety switch installed that prevented the starter from engaging unless the clutch pedal was pushed in all the way. I think maybe 74 was the first year.

Do you have a multimeter and know how to use it? It will be really helpful but not absolutely necessary.

Anytime there is a starting problem on the truck where the starter won't crank the engine over, I always like to isolate the starter and solenoid from the rest of the truck wiring.

I do this by jumping the large terminal on the solenoid to the small terminal on the inside of the solenoid next to the engine block where the purple wire is connected. This is called the S terminal. You need a fully charged battery, a good positive cable and good ground connections in order for the starter to turn.

This may create some sparks especially if you short the large cable to a ground, so I like to use a remote starter button to make the connection.It's nothing more than a couple of wires with alligator clips on the ends and a switch to connect them together.

Either way, jump the two terminals and you should get the engine to crank over. If you didn't pull the coil wire the engine may start because the outside terminal on the solenoid will carry 12 volts to the coil during starting even if the key switch is off. Normally the key switch will carry the ignition voltage to the coil after the starter disengages. Jumping it like I described only carries voltage to the coil while the starter is engaged. The outside terminal on the starter with a small yellow(usually) wire accomplishes this task.

So,--- if the starter turns the engine over with this test, we know that the starter and the battery and cable and the grounds are good and the problem is most likely in the ignition switch or the wiring to the starter.

looking at your picture you can see that the wires and the terminal plug appear to be in good condition in fact the wires look new.

Next thing to check is the large red wire in the ignition plug for 12 volts. That's where the multimeter comes in handy. This is the main power wire to the cab harness. It supplies the horn relay, the headlight switch, the fuse panel, and the ignition switch. It should be hot even with the key off, and it should connect to the terminal marked Bat.

Now check the rest of the wires for their correct connections to the key switch plug.
Pink to IGN, Purple to ST., Brown 12 gauge and smaller brown with white stripe to the ACC terminal.

You should have a couple of smaller brown or tan wires connected to GND terminal and if you have the idiot light dash cluster you should have a set of dark green wires connected to another GND terminal. The brown/tan wires are for checking the brake warning light and the green wires are for checking the
temperature light in the idiot light cluster. These wires are not connected to the hot wires in the IGN switch at all and they just ground to the chassis when the key is turned to the start position.

OK to check the starter circuit at the key switch, the easiest way is to jump the large red and Purple wires with the key off and look for the solenoid to engage and the starter to turn the engine over. If it does then we can conclude that the key switch is not making the connection between the two wires and it is bad. If it doesn't turn over then the purple wire is not connected to the starter solenoid.

Here is where the difference between the two harness styles comes into play.
The automatic harness will have a break in the 12 gauge purple wire just above the steering column. This allows the use of the neutral start switch which also combines the reverse back-up lights switch. There should be a dark green and a light green wire in a plug for that. If you don't have the NSS but the wires are there then you will have to jump the two purple wires together to get the starter to work.

If the harness is for a standard shift then the purple wire will go straight to the firewall plug on the inside of the cab. and from the outside of the cab it runs from the plug straight to the starter solenoid. There is a possibility that the connections in the firewall plug are corroded so that the purple wire is not making a connection there and will not carry power to the solenoid.

We'll get into the engine not shutting off after you get the starter problem resolved.

Here are some pictures to help illustrate what I have written.


The ignition switch wires.





The firewall plug





the cab side of the firewall plug




The starter wiring jump the large terminal to the purple wire terminal.

[VetteVet]

I see the boys are way ahead of me. I took too long typing LOL!


Here's another picture of a neutral start switch. The curved plug is for the turn signal switch.

[franken]

There are or seem to be a few problems.
1st, if the key on doesn't make key on stuff work, then does the key in the start (all the way right) not make a click or crank the starter?

The point is, you should look at this not from, it doesn't work, but from this part doesn't work. Break it down.

Do you have a horn or headlights?
Do you have dash lights or a radio?
Do you get a click or a grr when trying to start?

If it starts but won't shut off, I'd disconnect the big red wire at the alternator, and test. If it shuts off, that's a bit of wiring that isn't the problem.
The issue is related to switching power to the ignition off. Is this an HEI?

You need a voltmeter.

What's the voltage at the battery?
And so on.

[wilkin250r]

I just want to give a big thanks to Vette for going above and beyond the call of duty!

[Sinfulsaint24]

I won't be able to get under until tomorrow. I'll below is what I have found online. To what do the brown brown and green wires go? I don't have the green ones. Is that the Nss? This a 4spd. Thank you all for the help!

[ray_mcavoy]

Originally Posted by Sinfulsaint24

I'll below is what I have found online. To what do the brown brown and green wires go? I don't have the green ones. Is that the Nss? This a 4spd. Thank you all for the help!

As VetteVet explained earlier, the brown & green wires you're seeing off to the right in that photo you found online are:

Originally Posted by VetteVet

You should have a couple of smaller brown or tan wires connected to GND terminal and if you have the idiot light dash cluster you should have a set of dark green wires connected to another GND terminal. The brown/tan wires are for checking the brake warning light and the green wires are for checking the temperature light in the idiot light cluster. These wires are not connected to the hot wires in the IGN switch at all and they just ground to the chassis when the key is turned to the start position.

The lack of green wires on your ignition switch is normal if your truck has the full gauge cluster instead of warning lights.



Also, in taking a second look at the photo of your ignition switch connector you posted earlier, I noticed that your pink ignition wire appears to be connected to the "G-1" ground terminal instead of where it's supposed to be on the "IGN" terminal. The pic you found online does have the pink wire in the correct location.

[Sinfulsaint24]

Tried jumping the starter. I got sparks, but nothing else. Also used a multimeter on the two red wires, nothing as well. I'm going to replace the starter and find a way to get power to the switch. Looks like I will invest in a new harness as well. Any suggestions? Wiring isn't my strong suit (obviously) so the easier, the better!

[Sinfulsaint24]

Also, it is an HEI, I have 12v at the battery, love lights do work.