Sunday I took my 48 out to a local Pizza shop who was having a cars and calzones, only,1.2 miles away. I was just starting to signal for the turn into their lot when she shutdown. I coasted into a parking space and she was dead. Cranking did nothing, my gut said no spark. I checked by pulling a plug wire and placing it 1/2” from the plug, nothing.

So I walked, got my tools, and asked a neighbor to help me out, tow me home if necessary. We did the usual checks, fuel, good, spark, nothing, voltage at the coil, 3V, not so great. With the sun setting, and my friend nervous about towing her, we decided to call AAA. The flatbed was there in about an hour and got her home.

Today I once again went through the usual checks, still 3V at the coil, but now I have spark. She fired right up.

Not satisfied, I pulled the ignition switch and checked for any faults, excess resistance, etc. I checked all the grounds, every connection (ok both connections) and everything checks out. I drove around my neighborhood for 20 minutes, and left her idle in the driveway for another 20 minutes. No problems.

I’m stumped, and nervous about taking her more than a few blocks away, I don’t want to get stuck.

Thoughts?

 

How EXACTLY are you measuring the 3V?

What happens if you remove both the (+) and (-) from the coil, and take a Voltage measurement at those wires? (Be sure to rotate the engine so the points are closed and have the ignition in the RUN position). You should have battery voltage (A nominal 6V)

 

Does it have a ballast resistor fitted ?
if so it may be faulty .

 

It shouldn't have a resistor.

 

I should’ve mentioned, I have a pertronix module installed, no points.

I measured from the coil hot side to ground.

 

You measured from the coil (-) terminal to the battery (+) terminal and got 3V?

Disconnect the coil (-) terminal, and measure the voltage from that wire to the (+) terminal of the battery with ignition in RUN. It should be 6V. If not, check your wiring from the coil to the ignition switch.

 

I am betting it is your Pertronix module. As good as I think they are, sometimes they start getting intermittent. Just my experience with one of them. In talking to their Tech Support they told me to test it this way (if I recall correctly. )

Take a 6 volt test light bulb and connect (assuming your ignition is + ground) from the + side of the coil to a good ground with the + wire STILL connected to the distributor. It should flash with the engine turning over. If not, you have a bad module.
There should be some thermal insulating paste I believe under those modules to help dissipate the heat. Is there?
Also in talking to other folks about those. They don't like low battery voltage. Especially if it happens to be a Pertronix Ignitor II module.

EDIT:

Just another quick tought, Is you coil a Pertronix also? Just asking as too low of resistance coil will cause those Pertronix modules to run hot and could
eventually damage them.

 

Thanks, this is very helpful.

Yes, it’s a pertronix coil as well, and yes, these things hate low voltage. I had trouble with the stock generator, it simply didn’t supply enough current to keep the battery up to full charge. it’d backfire, ping, and do all kinds of nasty stuff. I replaced the generator with a powergen alternator and it’s been great.

Im ordering another Ignitor II before even running the test,

 

So the module tests good, but I’m not surprised. My suspicion is that it didn’t fail until it was hot. There isn’t any thermal paste under it, I don’t remember the instructions calling this out.

Since I’ve eliminated everything I can, I’m going to replace the module. I ordered it from pertronix and it should be here in a few days,

Thx to everyone who replied, especially hooler.

 

I still don't see that you have reported that you are getting a decent 6 volts to the coil. That low voltage of 3 volts could explain the flakiness and issues with the rest of the ignition system. While you've already ordered a new kit, I would be wary of just slapping it in before validating that you've got good power to the system.

The test as hooler describes, bypasses the coil feed and the coil leaving those as potential places for issues to remain.

I'm not saying that your pertronix isn't at fault as they are are known for failing like this, but it is smart to cover all your bases so you don't somehow damage your new unit (or could have saved you some dollars before jumping the gun).

 

Hey Bob!
I know you already ordered it, but it was an Ignitor ll that I had problems with too.And it sounds like very similar symptoms I had. In fact I nursed my truck home for 70 miles with the same issues going on. The engine would die, sometimes the ignition came back and the engine would run again, being spun over by the transmission at 55 mph, other times it wouldn't start, and I would have to let it sit for 20 to 30 mins. Finally got it back home and it died again pulling into my driveway and it would not run again with that particular Ignitor II module.
Turns out the Ignitor II has a reputation of dying this way. I spoke with someone at Pertronix, who advised me to upgrade to the Ignitor III, but he told me I could keep using the II coil. That's exactly what I did and that was some 8 years ago. I have had no problems since. The Ignitor II coil has a higher resistance and doesnt make the III module work as hard so you have a safety margin built in for the module in that set up.
So my recommendation is try to upgrade to the III module if you can. (If it's available for your truck that is).

 

My bad, I did check the voltage and yes I have 6.3V at the coil. 2 possible reasons I wasn’t getting an accurate reading, 1; I was measuring the voltage drop across the coil, not the input voltage, and 2: the stator was in the wrong position. I disconnected the ground wire and was getting 0v so I rotated the engine slightly and it went right to 6v.

 

Well, I haven’t been able to get in contact with Pertronix, but their website doesn’t show anything in 6v + ground other than the original Ignitor. I was on hold for almost 30 minutes, so I gave up and sent an email.

I actually purchased from the Pertronix store on Amazon so free returns. If they make the Ignitor 3 I’ll get that. When I bought the module, they said this was the only 6v + ground they manufactured, but that was over 2 years ago.

FYI, I don’t have a 6v test light, so I hooked up my meter and rotated the engine by hand. I could see it go from 0 to 6v easily. My best guess is that it will work fine until it heats up.

 

Gotcha!

Sorry Bob, I thought you were already using a Pertronix 2. My bad. And I doubt they make a Pertronix 3 for a 6v positive ground. But it's been several years since I shopped for one. The Pertronix 1 has a good reputation. As far as I know it's just a hall effect switch. Do you know if your Ignition was accidentally left on with the engine not running? Like another family member moving the truck, accidentally killing the engine, and walking away from it without shutting off the key? I could see something like that damaging that module if the engine happened to stop at a place where the points were closed and the key left on. One thing about the Pertronix 2 and 3, it will time out and automatically open the circuit from the coil if the key is left on and the engine not running thus saving itself.

 

I believe you’re correct about it being a Hall effect switch. No one else drives my truck and I’m careful about removing the key after I drive, but it’s not impossible for me to have made a mistake.

My suspicion is that without a good solid physical contact to the dizzy and without thermal paste, it simply overheated and shut down. I’m not comfortable driving any distance to test that theory, but I’ve driven around my neighborhood a few times without any trouble. Once I get the new module I’ll be braver.

Thx for all the help, this is the best forum in the world.