Not getting power to coil
 

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

Re: Not getting power to coil
 

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?

Re: Not getting power to coil
 

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

Re: Not getting power to coil
 

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?

Re: Not getting power to coil
 

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".

Re: Not getting power to coil
 

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.

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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.

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

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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/carp...istributor.jpg

Re: Not getting power to coil
 

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.

Re: Not getting power to coil
 

And I guess these electronic ignitions do not have condensers.

Re: Not getting power to coil
 

Okay lemme go test the plug the way you said.

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

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Okay definitely no spark at plug.

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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.

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See next step above

Re: Not getting power to coil
 

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

Re: Not getting power to coil
 

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.

Re: Not getting power to coil
 

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.

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I did send you my email in PM

Re: Not getting power to coil
 

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.

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

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

Re: Not getting power to coil
 

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.

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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.

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

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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:

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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.

Re: Not getting power to coil
 

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

Re: Not getting power to coil
 

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!

Re: Not getting power to coil
 

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 seems to be the one. Double check.

Re: Not getting power to coil
 

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

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Here's a pretty good pic of the label on the side https://drive.google.com/file/d/1MOv...w?usp=drivesdk

Re: Not getting power to coil
 

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

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https://instagram.com/stories/newyor...um=share_sheet pic @ instagram:pullinghairout:

Re: Not getting power to coil
 

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.

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

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Thanks Fetch will post Youtube that way!

Re: Not getting power to coil
 

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.

Re: Not getting power to coil
 

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: