Wireing problems

[stepside68longbed]

I just got a 68 orginal 307 to shine up it was running when I got it they had the starter bypassed by running a wire strait from the starter coil to the positive battery post. I went and had the starter rebuilt, changed sparkplugs, oil, antifreeze, new battery. Got the starter back put it on wired it up ran the wire from the coil back to the battery like it was and it won't turn over at all the lights did come on. We got bad weather so I couldn't work on it now the lights won't even come on I charged the battery and still no lights I've looked at wireing diagrams to see how everything is suppose to go (hate wireing problems) everything checks out to but an extra white, yellow, and I think a green wire from the main engin harness that runs along the the firewall that come out by the heater box. Not sure where they are suppose to go and not sure how the wire is suppose to go that's comeing from the starter coil I think it suppose to go to the S terminal on the starter with the yellow and purple on the R terminal. Any suggestions please!!

[ray_mcavoy]

Welcome!

The purple wire should go to the "S" terminal. That wire leads back to the ignition switch "SOL" terminal and should be live with the key in the start position. If it isn't, check the neutral safety switch (if it's an automatic trans).

The yellow wire should go to the "R" terminal. This wire is used to bypass the resistance wire, feeding full battery voltage to the coil when cranking the engine. A problem with this wire won't keep the engine from cranking over though.

As for the lights, do you have power to anything else in the cab or is it completely dead? If it's completely dead, check for power on the junction block that's on the fender near the battery. No power there means the fusible link connecting it to the positive battery terminal is bad or doesn't have a good connection. If that checks out okay, the next place to look would be for a bad connection in the bulkhead connector on the driver side of the firewall behind the fuse box. In particular, check the terminals on the large red wire ... that's the main feed wire that powers the fuse box, headlight switch, and ignition switch.

[JimKshortstep4x4]

Welcome to the 67-72 Chevy Truck Forums from West Michigan!

The green wire is for the temperature gauge (or light) and would route to the drivers side head where the sensor is located on a V-8.

The yellow wire goes to the outside post on the solenoid and the larger purple wire goes to the inside post next to the engine. The purple wire gets power from the ignition switch via the neutral safety switch if you have an automatic transmission.

Jim

[stepside68longbed]

So the green is the temp gage, purple goes on the R and yellow on the S and the yellow Is the neutral safety, the guy said it would start in gear why he would do that in an automatic I don't know but that means that the neutral safety isn't hooked up. And the wire from the starter coil goes where? It's not colored they just put some 12 gage wire to replace whatever was there... The things you find out AFTER you buy a truck is so disappointing.

On another note is there a good/ cheaper way to clean a gas tank I checked into having it cleaned and powder coated they would cost 250 all said and done lmctruck has a new gas tank for 200. I didn't know if there's a cheaper alternative.. And thanks for the help

[stepside68longbed]

Switch the yellow and purple on my reply.

[ray_mcavoy]

Originally Posted by stepside68longbed

So the green is the temp gage, purple goes on the R and yellow on the S and the yellow Is the neutral safety, the guy said it would start in gear why he would do that in an automatic I don't know but that means that the neutral safety isn't hooked up.

Switch the yellow and purple on my reply.

Yes, green=temp sender, purple=S, and yellow=R.

Sounds like the neutral safety switch was bad and the former owner simply bypassed it instead of replacing it. It's a good safety feature to have so I'd recommend adding a new neutral safety switch to your to-do list once you get the other wiring problems sorted out.

Originally Posted by stepside68longbed

And the wire from the starter coil goes where? It's not colored they just put some 12 gage wire to replace whatever was there.

Does the truck still have a points distributor or has it been converted over to electronic ignition such as HEI?

If it still has the original points setup, it should have a resistance wire (or a replacement ballast resistor) feeding power to the coil. But given the 12ga wire, I'm guessing that it's been converted to HEI. If so, that wire should go back to one of two places (depending on how they hooked it up). One option is to run it to the bulkhead connector terminal that originally fed the resistance wire. The other option is to run it inside the cab and plug it into the "IGN" terminal on the fuse box. In either case, it should receive power from the ignition switch "IGN" terminal in both the start & run positions.

Oh, and if it has been converted to HEI, that yellow bypass wire going to the starter isn't really needed any more. It won't hurt anything to leave it hooked up though.

[stepside68longbed]

Originally Posted by ray_mcavoy

If it still has the original points setup, it should have a resistance wire (or a replacement ballast resistor) feeding power to the coil. But given the 12ga wire, I'm guessing that it's been converted to HEI.

No it's still points its not the wire in the middle, this wire that they afroengineered on here was from (I think) the postive side of the coil it had to be hooked to the positive battery post to start and unplugged to shut the truck off. I don't know where this wire is supose to go, I thought the yellow and purple went on the inside terminal closest to the engine and this wire they had from the coil went to the outside away from the engine?

I should get to the farm tomorrow and I will take a few pics. As well as put the yellow on the outside post and the purple inside and I guess hook this wire from the coil back to the battery...? and check for the junction block connection and see what happens.

Where is that wire supose to go? because I won't feel like popin my hood and unplugging the wire just to shut my truck off. I thought about getting a new ignition switch but I wanted to make sure that's what I needed. And I can't tank you enoghf this has been such a headache!!

[ray_mcavoy]

Originally Posted by stepside68longbed

No it's still points its not the wire in the middle, this wire that they afroengineered on here was from (I think) the postive side of the coil it had to be hooked to the positive battery post to start and unplugged to shut the truck off. I don't know where this wire is supose to go, I thought the yellow and purple went on the inside terminal closest to the engine and this wire they had from the coil went to the outside away from the engine?

Okay, I see what you're dealing with now.

Originally Posted by stepside68longbed

I should get to the farm tomorrow and I will take a few pics. As well as put the yellow on the outside post and the purple inside and I guess hook this wire from the coil back to the battery...? and check for the junction block connection and see what happens.

Yes, that would be a good start. Also, take a close look at the coil to see if it's marked "use with external resistor" or something similar.

Originally Posted by stepside68longbed

Where is that wire supose to go? because I won't feel like popin my hood and unplugging the wire just to shut my truck off. I thought about getting a new ignition switch but I wanted to make sure that's what I needed. And I can't tank you enoghf this has been such a headache!!

The original factory wiring had 2 wires attached to the positive side of the coil. The yellow wire (as mentioned earlier) should go down to the outside "R" terminal on the starter solenoid. The other wire was a special resistance wire that ran back to the bulkhead connector on the firewall. From there, a pink wire connects to the "IGN" terminal on the ignition switch.

The resistance wire (if it's still present in the harness) is easy to identify because it'll have a solid core (not stranded like all the others) as well as a special woven cloth-like covering. If that wire is gone and you have a coil that requires an external resistor, the easiest fix is to get a replacement ballast resistor and wire it inline with the wire feeding the + side of the coil.

The wiring diagrams that hatzie scanned & posted at http://67-72chevytrucks.com/vboard/s....php?p=5781194 will probably come in handy for you to see how the factory wiring was connected and where the coil feed wire is located in the bulkhead connector.

[stepside68longbed]

Well I went and looked at it, the coil does say primary residences wire or external resistance. The junction block is connected fine. I traced the Maine red wire from the junction block an there's this sort of old fuse (its broke) on the wire do I need to replace that or can I just splice it and put them together? I'm not sure how to upload a photo on here.

[ray_mcavoy]

That main feed wire originally had a fusible link at the end where it connects to the junction block on the fender near the battery. Sounds like someone replaced it with a fuse.

I'd recommend keeping some sort of protection on that wire ... otherwise, the whole wire can melt down and potentially start a fire if it gets shorted out or overloaded. Either install a new fuse or go back to the original configuration that uses a short section of 16ga fusible link wire to protect the 12ga main feed wire.

Edit: I forgot to mention, if your truck has a factory gauge cluster, there should also be a smaller black wire for the ammeter connected to that junction block as well. That wire originally had a small inline fuse holder with a 4 amp fuse. Not having the ammeter hooked up won't keep the engine from starting but I just thought I'd mention it in case your truck has that wire and you were wondering where it went.

[stepside68longbed]

I think it's an old fuse I ain't seen them before.

[stepside68longbed]

[stepside68longbed]

You see the big red wire that is your Maine feed correct?

What I the smaller wire for the one with the old fuse?

[stepside68longbed]

This is the the wire that is tan to the battery, to start the truck you hook it onto the positive post on the battery, to kill it you have to unhook it from the battery. I don't know where this wire is suppose to be ran.

I hook the purple wire onto the inside terminal and ran this wire back to the battery, and still nothing. I hope if I fix that fuse on the smaller red wire coming from the junction block then I will get some sort of reaction... hopefully even start.

[ray_mcavoy]

Originally Posted by stepside68longbed

You see the big red wire that is your Maine feed correct?

Yes, that is part of the main feed wire. However, it doesn't look like it is complete. There should be a section that runs from the junction block, across the radiator support towards the driver side of the truck and eventually ends up at the bulkhead connector on the firewall.

Originally Posted by stepside68longbed

What I the smaller wire for the one with the old fuse?

The wire on that fuse holder looks to be a bit on the small side to have been a replacement for the fusible link in the main feed wire. It could have been a replacement for the ammeter fuse though.

Here's a pic of the junction block on the fender of my 72 with the wires labeled:

Originally Posted by stepside68longbed

This is the the wire that is tan to the battery, to start the truck you hook it onto the positive post on the battery, to kill it you have to unhook it from the battery. I don't know where this wire is suppose to be ran.

That wire should be run back to the bulkhead connector on the firewall. See the diagram I posted below. And according to your coil, it needs an inline ballast resistor since you probably don't have the stock resistance wire anymore.

Originally Posted by stepside68longbed

I hook the purple wire onto the inside terminal and ran this wire back to the battery, and still nothing. I hope if I fix that fuse on the smaller red wire coming from the junction block then I will get some sort of reaction... hopefully even start.

Do you have power to anything in the cab of the truck? From the looks of the pic showing the junction block, main feed wire, and old fuse holder, it doesn't look like the main feed wire is hooked up from the junction block onward.

Here is a wiring diagram that should help you figure out where the wires go.



I added some coloring to the wires in question to make them easier to follow.

Red = main feed wire.
Yellow = bypass wire from starter "R" to coil +.
Purple = starter solenoid wire to "S".
Orange = Coil + feed wire (this was originally a resistance wire with a white/orange/purple cloth like covering but can be replaced with a regular wire & a ballast resistor).

[stepside68longbed]

So I need two wires from the coil one going on the outside R terminal and the othe going to the engin harness. I have some 16 gage speaker wire woul that work for either of them or does it need to have a thicker cover?

My main feed wire the bigger red one does go from the junction block across the radiator to the drivers side then it it wraped in electrical tape and then 2 wires come from that I didn't get a picture of that. But would the inline fuse stop everything?

And I have no power at all nothing no head lights I didn't check the breaks no horn or anything. It did all work hazords lights breaks horn it ran and all then I did all that stuff in my first post and hasn't worked sence I wonder if when I put the battery in that it broke that inline fuse.

[ray_mcavoy]

Originally Posted by stepside68longbed

So I need two wires from the coil one going on the outside R terminal and the othe going to the engin harness. I have some 16 gage speaker wire woul that work for either of them or does it need to have a thicker cover?

Yes, 2 wires from the + side of the coil. You might want to take a close look at your engine harness to see if the factory resistance wire is still in there ... the previous owner might have simply unhooked it and left it in the harness when they added that other wire that's on the coil now.

The 16ga speaker wire will probably be okay for a temporary fix. But the insulation covering might not hold up all that well to the engine heat for long term use.

Originally Posted by stepside68longbed

My main feed wire the bigger red one does go from the junction block across the radiator to the drivers side then it it wraped in electrical tape and then 2 wires come from that I didn't get a picture of that.

There is a factory splice in that main feed wire in that location for the wires that branch off to the alternator & voltage regulator. As long as those two wires are still hooked up to the alt & reg, you should be all set. If they're not hooked up, it won't keep the engine from starting but the ends should at least be taped up temporarily to keep them from shorting out on anything until you do hook them up.

Originally Posted by stepside68longbed

But would the inline fuse stop everything?

If that fuse was indeed used to replace the factory fusible link (and it's inline with the main feed wire) then yes, it would cut power to everything.

Originally Posted by stepside68longbed

And I have no power at all nothing no head lights I didn't check the breaks no horn or anything. It did all work hazords lights breaks horn it ran and all then I did all that stuff in my first post and hasn't worked sence I wonder if when I put the battery in that it broke that inline fuse.

That could be it. I'd recommend replacing that fuse holder with a larger/heavier one or going back to the stock type fusible link wire as I mentioned earlier.

[stepside68longbed]

Got it running got an inline fuse and tightened everything and found the wire from the bulk head and it split into two yellow wires i put one on the (+) coil and the other on the outer terminal and oil is leaking from somewhere now... If it ain't one thing it's something else ill look further into that tomorrow. Thanks for all your help thus far!!