Not getting power to coil

[newyorksong]

Hi guys! Well my 1965 GMC 1000 just would not start after some very heavy rain. At first I thought the system was getting soaked and shorting out, or the coil was bad, but after buying a new coil now (no change) I think the yellow and black wires going to the coil positive might not be working.

The yellow and black wires go through the wall into what I don't know.
Any ideas?

Guess I'll see if the black is carrying 12 volts. Electrical is my weakest subject though it's a contest.

Thanks for any help
Roger

[AZKen]

Whoa there Roger. Let's don't buy any more parts. You have reached the right place. We can get your truck started. First let's get the terms straight. "Won't start" I assume means it cranks just fine but will not even fire once? Starter is turning at good speed? I don't know why you think it is electrical. It could be. But it also could be fuel delivery or timing. Testing is the key right now. If you have a ice pick voltage tester or a multimeter, turn ignition key on and see if there is 12V at coil positive terminal (yellow wire). Don't try starting, just key to "on". Report. One step at a time. Answer all questions carefully.

Have you or anyone been messing with the motor or electrics? Is carb popping, backfiring, sputtering?

[newyorksong]

Hi Ken Thanks for responding. I went out and used my multimeter and the yellow wire (which also has a black wire on the positive terminal) showed 12v key on.
The negative of coil also had 12v.

No one has messed with it I just had it parked for a few months but always started it frequently until the rain and cold hit then one day it had trouble starting I gave it a lot of gas and the muffler blew apart like a grenade!

Since then it has started with worsening condition until it just quit for good.
No spark out of the coil.
Rog

[gmcjuniorvan]

Electrical is not my thing so just a thought.
If you have 12v on the negative side of coil the points are open. That means when you check it they happen to be open or they are burn so bad they do not close all the way, you have a gap between them. . Have you checked the points?

[AZKen]

The next step is to remove a sparkplug. Attach it's wire to it. Touch the threads on a good clean metal ground spot on the motor and crank motor to observe spark. Hard to see in daylight, so watch carefully.
The backfire was probably your pumping gas, unburnt gas, into the system. It can also be something worse. Do the plug test and be sure of your result, very important.
I assume the negative on coil has a black wire to the distributor??????????? and that wire is not frayed and touching distributor housing.
I agree, probably time for new points and condenser of there is weak or no spark at plugs.
Explain specifically how you tested to get "no spark out of the coil".

[newyorksong]

How do I know there is no spark from the coil? Well your not gonna like this, no good mechanic does ... but I've been doing it for over 50 yrs and for me it is VERY accurate. What I do is HOLD the wire (from the coil or from a plug) as I put it to a spot on the engine, and believe me when I say I KNOW when I have a good spark or a weak spark or none! I could probably almost read you out the amperage by the tingle in my teeth. Embarrasing yes but there it is.

[newyorksong]

BTW there are no points as the guy that had it before me put in the (what is the correct name?) electrical points thing. I could get a new condenser or a replacement electric points AND condenser if you think I should do that.

BTW pretty sure the carb may need to be rebuilt and I'm kinda short on $ right now so might have to do that myself but I am NOT very good a that kinda detail stuff.
Probably will have to do it. But right now I just need the truck to start to keep it oiled.

[newyorksong]

Okay looked it up it's an electrical ignition. Sheesh Hmmm wonder it that could be bad?

[newyorksong]

Don't know why pic is not showing but will put link here. Don't worry link is judt to my paid server and is okay!
http://syphan.phpwebhosting.com/carpics/65coil_distributor.jpg

[AZKen]

Pertronix. There are good and bad reviews. The earlier versions had a lot of trouble. If I am helping someone with just words, which is VERY difficult, I have to do it a certain way, like you do. Unfortunately, I can't trust everything a person says and I have to have tests before I start jumping ahead or guessing. It's real easy to shoot out a dozen guesses. So let me know if there is spark at a spark plug. Maybe this one time you can look for a visual spark ay a plug like I described. I've been doing it that way for more than 60 years. We will establish spark and get truck started. Does not matter if fuel delivery is bad. Getting spark is No. 1 priority.
If you find no spark at a plug you can either revert back to points or we can try to troubleshoot the Pertronix/buy another.

[newyorksong]

And I guess these electronic ignitions do not have condensers.

[newyorksong]

Okay lemme go test the plug the way you said.

[AZKen]

No condenser. Measure the gap between the black round piece and the little rectangular black box. Needs to be .030

[newyorksong]

Okay definitely no spark at plug.

[AZKen]

TAKE OFF NEGATIVE BATTERY CABLE.....Measure the gap between the black round piece and the little rectangular black box. Needs to be .030. I'll stay with you at my computer. Tell me when you get tired and I will go eat dinner. Better faster to use email at this point. If you wish, PM your email address.

[AZKen]

See next step above

[newyorksong]

Never really looked closely at these before. .030 does fit but a bit tight feels more like the .028 slid better. But does go.

[AZKen]

Close enough. Check all the wires and their terminations. Then one final test before declaring the unit dead. I will post that in a minute.

[newyorksong]

From the Pertronix the red wire goes to the coil positive and the black wire goes to the coil negative they look solid. The positive on the coil also has the yellow and black wire that comes from the firewall.

[newyorksong]

I did send you my email in PM

[AZKen]

Take off distributor cap, leave plug wires on it.

Take the red and black wires of the Pertronix off of the coil and do this with them. (You will have to reconnect the negative battery cable I told you to disconnect)


1. Connect a jumper wire from the Ignitor Plate to battery ground post. this is the plate inside the distributor that the Pertronix stuff is mounted to.
2. Connect the Red wire from the Ignitor to the battery positive terminal along with the red lead from a volt meter.
3. Attach the Black wire form the Ignitor to the black lead of the voltmeter.
4. Move or rotate the magnet sleeve (black round piece) in front of the Ignitor Module (black box), the voltmeter should vary from battery voltage to 0 volts and back. So should see 12V.....0......12V....0....as you as you rotate it by hand or crank motor.

[newyorksong]

What is the magnet sleeve? Is that the black ring? That only moves about 1/4 of an inch or so.

[newyorksong]

Ah I see I can crank the engine and watch, hooking up multimetter now

[AZKen]

Yes, the black sleeve. Those are the instructions from Pertronix. I agree they did not explain why they say "by hand or crank motor". You will have to crank motor I guess, I'm not up on this test. Just be careful that wires are safe from touching anything or get caught in a moving part. Rig it up, shouldn't have to crank much to get a reading on MM. It's either going to stay on zero or stay on 12V during rotation if it's bad.

Do you have a ballast resistor?
Does coil say internally resisted or externally resisted on it?
How long has the motor been running good and starting good. days, months, years?
FYI: Older (first generation) Pertronix would burn out if key left on.

[newyorksong]

Okay hope I got that mess right. Think so. It wasn't changing much showed between 8v and 6v and 7v and 8 etc during cranking.

[newyorksong]

What with being 73 and my back, and it being freezing out it's a bit of a challenge.

[FetchMeAPepsi]

I don't know a thing about petronix, but reemember that that gray wire from the key is a resistor wire and runs 6 volts. I know you're talking about the connections at the igniter, but saying it ran from 6-8 volts made me want to speak up.
I'll go back to watching now :cheers:

[newyorksong]

This 305V6 has run perfectly ever since I got her a few years ago. Then I started having trouble turning her (my shoulder) without power steering and finally found a 73 Chevy G10 Van with a 250 and 3 on tree and power steering. MUCH easier on the shoulder so I parked the GMC though I keep her tab current. So she has been sitting about a year with me starting her every few weeks. Then winter hit and the Chevy Van quit. So I tried to bring my GMC back but she wouldn't start. A lot of work and new carb has the 73 Van going but I don't feel too confident without my pickup running, These are my only vehicles they are my daily runners and without them I am going nowhere.

[AZKen]

Fetch, the test is done with coil not in the circuit. So the resistance wire is not either.
OK New York. let's go back after it when conditions are better, body and temp. That unit is supposed to make and break like points. Doesn't seem to be doing that. So gotta decide what to do. Price wise and reliability wise. Talk tomorrow.
Can you post a few pics of your test set up?

You didn't answer a few of my last questions

[newyorksong]

Ya Ken got a bit too cold out there tonight. Tomorrow I will re-rig it and take pcis along with new readings. Don't want to go back to points though, hate that adjustment. Thanks so much for the help!

[AZKen]

You are welcome. It's very hard for me to decide what version of pertronix you have. I, II or III. See if the label says.
Your distributor and surrounding area is very dirty/rusty. It needs to be pretty clean. I think debris has fallen on it while you were messing with it. Not your fault. DO NOT TAKE THE DISTRIBUTOR OUT.
I am NOT a Pertronix expert or even close. You don't have a III, you have a I or a II, I'm guessing a I (original Pertronix). If it is, It's gotta go in the trash. Get a II. This (https://www.amazon.com/PerTronix-91162A-Ignitor-Adaptive-Cylinder/dp/B000JUXGEI/ref=asc_df_B000JUXGEI/?tag=hyprod-20&linkCode=df0&hvadid=312057677264&hvpos=&hvnetw=g&hvrand=14717784407427442272&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030070&hvtargid=pla-592347930394&psc=1) seems to be the one. Double check.

[newyorksong]

https://youtu.be/QLVH9xD5v-o Testing video

[newyorksong]

Here's a pretty good pic of the label on the side https://drive.google.com/file/d/1MOvStbLn6eD-qYJeuTywZwHGFKg-DWLH/view?usp=drivesdk

[newyorksong]

Looks like D-57-2 or D-S7-2

[newyorksong]

https://instagram.com/stories/newyorksong2/2789018928016239289?utm_source=ig_story_item_share&utm_medium=share_sheet pic @ instagram:pullinghairout:

[AZKen]

Looks like you did it as the instructions say. If the instructions are viable. D-57-2 is a California document that states that Pertronix does not reduce emissions but it can be used on 83 and older vehicles in CA. I think.

Pictures are posted as follows. Click "Go Advanced" at bottom of post. Click the paper clip at top of advanced page. Window pops up. Select pic files from your computer. Upload pic. Close window. You won't see the pic until you save the post and it goes live.

[FetchMeAPepsi]

https://youtu.be/QLVH9xD5v-o Testing video
You just hit the Youtube button above the text box then paste the video code alone, without https://youtu.be/
QLVH9xD5v-o

[newyorksong]

Thanks Fetch will post Youtube that way!

[newyorksong]

Sheesh $100 plus for the Pertronix, and some others were saying I should also have a Pertronix coil for a good match, I wonder if I should consider going back to points if it would be much cheaper. I'm not actually running the truck right now just wanna keep it working well and self lubricating the engine. If I did try to go back to points I might have to find or buy the plate the point go to ... don't think I got the old dist plate when I bought it.

[newyorksong]

Okay well the Pertronix coils are around $40 so for a total of around $140 I guess maybe the igniter might be doable lemme talk to the boss (My wife Dinah) and see.:banghead:

[AZKen]

You don't need a Pertronix coil. No No No. Use the one you have. Take all wires off of coil. Set MM to lowest ohm reading. One MM lead on pos, one lead on neg. Read ohmage. Ignitor II can use any coil with 0.6 Ohms or greater. This will all be explained in the Ignitor II instructions.
They do recommend bypassing the resistance wire. We will discuss wiring the Pertronix if/when you buy it.

[newyorksong]

Okay purchased the Pertronix 91162A Ignitor ll Will get it weds and install it.
Fingers crossed! And Thanks for all the help.

[AZKen]

I just added, then deleted, a whole spiel...That ended with buy points. If you got it at Amazon, you can change your mind. Sorry, after thinking it over and your situation and budget, I had to be honest. My timing was 15 minutes late.

[newyorksong]

Okay got the Pertronix. Measured the coil at 1.3 Ohms so that's good. Reading install instructions. You said best to omit the resistance wire?

[newyorksong]

Previous had not notched the dist cap as noted so doing that. So wires don't pinch.

[AZKen]

Instructions say you can do resistance or not. It's kind of a goofy situation. The way the have it shown is silly and a little misleading. I can explain if you wish but sometimes a truck's wiring is no longer original.

:shocked:I need to ask you to check some things before you go any farther.:shocked:

[newyorksong]

After installing and setting gap I tried to screw down the dist cap only to find it would not go. And that is because I had it backwards. So now I will cut yet another slot for the wire. At least I'm up to my usual standards of automotive work.

[newyorksong]

Okay ask questions. I did get the cap finished and on.

[AZKen]

I don't know if the original wiring on the coil was correct and need to see how the owner had it so we don't blow the new unit. On coil positive, you had a red pertronix wire, a yellow wire and a probable resistance wire. This is not per wiring diagram for 1965 and is not the way it would be done to use the resistance wire for pertronix. so..........the important thing is to tell me where the yellow and res wires went. You said firewall. Need more specific with pics if possible. Once I see all that, I can help you wire the new unit.

[newyorksong]

I don't want to use the resistance wire. But let me take a pic.
the yellow and black coming through the firewall were on the positive together and even fastened together in a clip, but they just separated so
I was going to ask anyway. Gonna get pic now.

[AZKen]

Ok good, explain where they go also. I understand you don't want to use the resistance wire.
Another thing, where there/are there any wires on the "R" terminal of starter solenoid? If so where do they go. This is info to help you, help others later and we may see why the other unit failed. Lets me advise on how to eliminate the resistance wire and wire the unit. You are at a good stage to supply info on the subject for the Club archives. Thanks.

Some of the Pertronix info/instructions about eliminating resistance wire or ballast does not seem apply to 60-66 GMC.

[newyorksong]

Sorry had to take a 30min course on how to use phone flash. Lets see if I attached this pic properly.

[AZKen]

I see some wires and some blurry stuff and a black window spider. But I don't know anymore than I did. Try another day. Read the post above. You may have forgotten again to look for responses. You must get into that habit. This is taking way too long because of that. I'm trying to stay on a roll so I don't have to relearn all this every other day.

[newyorksong]

Starter-pic

[AZKen]

OK, it's my fault. I should have never asked for pictures. I should have stuck with a full and precise explanation from you as to what you see and where each wire goes. Meaning it's other end and how it got there. I will say you are now an expert at taking and posting pics. That is wonderful. Just remember wiring is tricky. It's important not to make mistakes. Especially if you are advising someone from 2000 miles away trying to look at a pic.

Read the posts, read my questions, get me the info. The other option is to wire it up. I'm not saying I'm taking over this deal. You obviously know how to read instructions and install it. That would also save me from any responsibility. I only do what the voices in my head tell me to do. :beer:

[newyorksong]

Yup gotta rest ... below freezing now, and that Black widow is eyeing me like I'm the last juicy fly in town! It's always been a nightmare for me once it hits harness, but I'll try to figure by continuity where the black and yellow wire go.

[AZKen]

The idea of the ballast resistor, or later, the resistance wire, was to save the points. Make them last longer. Full 12V will burn them out PDQ. The resistance wire reduces the voltage to around 8-9 volts to the coil so that points last way longer. The starter takes a HUGE amount of amps and a lot of the 12V while cranking the motor. So much voltage; that you can't have it going thru a ballast or resistance wire to the coil during that time or there would not be enough voltage to fire the points/plugs.

So enter: the "bypass"
The original GMC wiring to power the coil was a pink wire from the ignition switch "on" terminal to the 6 pin connector mounted on the passenger firewall. As it came out of the connector on the engine side, it came out as a weird looking whitish, yellowish, oddly insulated nickel copper wire. The famous resistance wire. Which went to the "R" terminal on the starter solenoid. Also on the "R" terminal was a normal yellow wire. It went to the coil positive terminal. The operation of that "R" terminal is that it is dead most of the time. Dead meaning it does not provide any voltage. It's just a termination point for two wires. The resistance wire and the yellow wire. When the ignition switch is held at max clockwise for starting, The violet wire from the ignition "start" terminal sends 12V to the solenoid "S" terminal which energizes the solenoid, which causes the starter to spin. Voltage also flows from the ignition switch thru the pink, then resistance wire to the "R" terminal. But AH HA the solenoid has also given the "R" terminal 12V. This solenoid supplied voltage over rides or bypasses the lower resisted voltage from the ignition and sends full 12V thru the yellow wire to the coil. Motor starts, you let go, "R" becomes dead, now a termination point and coil only gets 8-9 V from ignition switch.

You don't have points so you don't need all that magic. You just need the ignition switch "on" terminal to supply 12V to coil positive for Pertronix. So two wires on coil pos, one on coil neg.
You don't need any wires to go to, or come from, the solenoid "R" terminal.

The reason I was asking where the wires went is:
1. I was looking for a wire to use for the coil and to see which needed taped off and/or coiled up to abandon resistance wire. If no switched power wire is found, you will run a new wire.
2. Trying to figure out why there was 3 wires on the coil positive. It's possible it was OK that way.
3. Wanted to confirm what Pertronix wiring instructions A. 2. says about following wire to fuse box and jumping is not applicable here.
4. Make sure I don't screw up.

One more aspect to this TMI saga. Back in 55-56, when GM went to 12V, which needed a resistance circuit, the starters did not have an "R" terminal. The situation was handled by the ignition switch alone. That's where you see "Ign-1" and "Ign-2" terminals on the ignition switch. You had a wire from each of those to coil positive. In start position, Ign-2 sent 12V direct to coil. Spring back to "ON" and Ign-2 was dead and Ign-1 sent 12V to ballast resistor. When folks reuse parts, they end up sometimes with an "R" starter and a Ign-1/Ign-2 switch. Then all h-ell breaks loose.

Keep notching that cap. I'm with you til the end.

[newyorksong]

Whew! Thanks for the detailed explanation. Since it ran for many years with no trouble with the 8v or so, I think I will go for it tomorrow and hook up as it was.
When I say go for it I just mean holding the plug to the engine to see if there is spark.
Pretty sure that initially it stopped running because of the carb but had plenty of spark and then I'm pretty sure I burned out the PerTronix l by starting it for days and battery charging another few days and prob leaving key on for a loooooong time as well. Hopefully the PerTronix ll doesn't burn out so fast.

So gonna give it a shot as is. What is the saying? "If it ain't broke don't fix it." Maybe the positve connections at the coil weren't broke. We'll know more in the morning. :ahhhh:

[gmcjuniorvan]

Electrical is not my thing so just a thought.
The coil runs on 8-9V. If you run 12v to an external resistance coil it could over heat and it burn out. After looking at the 64 wiring diagram. Its looks like the resistance wire start at the plug in the engine compartment. Disconnect it, turn the ignition switch to the run position. And check voltage at 18-p-3 on the R.H dash bulkhead connection in the wiring diagram. If 12v. Pull the resistance wire pin out and replace it with a new wire and connect it to the coil. Then connect the Pertronix to the coil.
Or disconnect the resistance wire from the coil turn the ignition switch to the run position. And check voltage on the wire it could be almost 12v. If it is then connect wire and the Pertronix to the coil.
I think the amount of resistance in the wire depends on the length of the wire, the longer the wire the more resistance. And the resistance wire should go to the "R" terminal on the starter solenoid.

And go I would buy an internal resistance coil just to be safe.


64 wiring diagram

[AZKen]

If it ain't broke fix it til it is.

By the way, it's tomorrow right now. Are you busy putting the fire out?

[newyorksong]

I wish, just went out and pulled the plug had my wife crank it and ... 1 weak spark and then none. :pullinghairout:

[newyorksong]

Got pissed off said " F-THIS!" Went and got my huge 750 cranking hours BRAND NEW Marine deep cell threw it in, hit it with 1 shot of starter fluid and she fired right up. I guess a little voice in my ear reminded me of this happening before when I bought a 95 Chevy van. Beautiful van but of course it's sitting in the yard now with no transmission. Duh.

The battery that was in my 65 was not holding charge so I would charge it then work, cranked really well for 3 minutes but I guess it never makes quite a hot enough spark if it's a shot battery!

Anyhow the whole point of this (for the short term) is just to be able to lubricate the engine for the time being. I do want her up but at least I can keep her from degrading.

I'm thinking it would prob be a good idea to put that bypass in at some point too.

And THANK YOU sooooo much Ken! Your calm reminders kept me (somewhat) sane!

[newyorksong]

A lot of work to do she gently backfires so I will try to rotate the dist as per the instructions in PErTronix kit. And the carb is pretty bad especially accelerator pump, but at least she starts right up.

[AZKen]

Good deal. I would suggest doing what the instructions recommend. No ballast, no resistance wire. Notice that 12V goes directly to the module no matter if resistance wire is used or not. This is the BIG MISTAKE folks make about using resistance with Pertronix. They wire it up like the points were wired. I fear that is what the other guy did.
Best to eliminate resistance altogether before you slow fry the Pertronix.

[gmcjuniorvan]

Electrical is not my thing so just a thought.
The resistance wire starts at the plug in the engine compartment. Disconnect it, turn the ignition switch to the run position. And check voltage at 18-p-3 on the R.H dash bulkhead connection in the wiring diagram. It should be 12v. If so pull the resistance wire and pin out of the plug and replace it with a new 18g wire and pin (not a resistance wire) and connect it to the coil. Then connect the Pertronix to the coil. No more resistance wire and 12v at the coil.

64 wiring diagram

[AZKen]

That's a lot of work and it's 6 extra voltage drop points, 6 extra resistive terminations and 4 feet of extra wire with some resistance.
A straight wire would be best.

[gmcjuniorvan]

That's a lot of work and it's 6 extra voltage drop points, 6 extra resistive terminations and 4 feet of extra wire with some resistance.
A straight wire would be best..

Is this about my post if so I do not understand what you are saying so please explain. If not explain anyway.

[AZKen]

Sorry, yes it's in regards to your post. Your idea will send voltage to the coil. That's true. I am describing the "tortureous path" of that method. Count the terminations and the length compared to one direct wire. I've seen you're other posts and I think you are more knowledgeable than you have said. So see what you think.