Need help for a '69 with no start/misfire (360 engine)

[gbass82]

I need some help/guidance because I am losing my mind right now. I have a 1969 with the 360 engine. Before she went down, she was running like a champ. one day, she was running and slowly started to miss before shutting down. This was about 3-4 months ago. Things that have been replaced prior to the issue; The entire distributor assembly (distributor, points, etc.), timing chain/timing gears, Coil, and plugs/wires. She ran for about 8 months before the current issue started. After investigation with some friends, we replaced the carburetor, intake manifold gaskets, and plugs (fuel fouled from bad carb). After getting everything buttoned up, she will start but will shut down after a minute or so. A restart attempt fails (she will turn over but not fire. We tripled checked the distributor/timing alignment which is good. It seems that we have a weak spark from the coil when we take it off, ground it and start the engine. Is there anything else that we can investigate? Wiring? Ignition switch? Anything info will be helpful. Thanks.

[Ranchero50]

Offshore condensers have been hit or miss for a couple years now... I spend time in junkyards and pull the nasty old ones out for spares. Or pickup a Pertronix unit and go that route.

[gbass82]

Thanks. I went ahead and tried another condensor. When I went to crank it up and she started but shut down after a few seconds. I attempted to start her again immediately but she didn't fire. Could I have 2 bad condensors (even though they are brand new)? I checked the coil and got a little over 6 volts at the positive post with the key on. I checked the voltage of the wire with it disconnected and it's 12 volts.

[sargentrs]

It is possible, even likely, to get 2 bad new condensers in a row. However, sounds like you're having issues getting the correct voltage to the coil. Should be about 9v with the key on. If you're getting 6v running and 12v not, I'd suspect the resistor wire from the ignition switch or the ignition switch itself. I also notice you haven't said anything about replacing the solenoid. Another possible issue with getting correct voltage to the coil.

[gbass82]

Thanks sargentrs. I failed to mention that the solenoid is new as well. We haven't looked at the ignition switch yet so I will definitely look at that next. Is the resistor wire pink by chance? I have also been researching the Pertronix unit that Ranchero50.

[Ranchero50]

The resister wire is pink and about 5' long between the ash tray and the ignition switch. It ties into the brown (I think) wire that runs to the 'ign' terminal on the solenoid at the firewall junction. That way the coil will be fed a full 12 volts during cranking.

Pop the dizzy cap off and make sure the points are open. Then you should read close to 8vdc at the points wire on the dizzy with the key to 'on'. When the points close it'll drop to 0 vdc and when running will be somewhere between higher. If it's not, work your way back to the battery through the wiring and ignition switch to find the resistance.

[gbass82]

Good stuff. I'll check out everyone's suggestions. Thanks for the help so far.

[tnlprt]

Run a jumper wire from the positive on the battery to the positive on the coil

See if it stays running

[gbass82]

I'll give that a shot tomorrow and let you know what happens.

[gbass82]

Tried a few things and replaced a few things. Ran a jumper wire from the battery positive to the coil positive as you suggested tlprt but no luck. I pulled out the ignition switch and checked the continuity with the wires (which was good). Since it was out, I went ahead and replaced the switch. She fired right up then shut down almost immediately. As you suggested Ranchero50, I opened the cap and checked the voltage. With the points open, I got 12 volts with the key on and 0 volts with points closed. What should I read at the ignition coil?

[Ranchero50]

When you jump from the batt + to the coil + you isolate all the other wiring and the ignition switch. If it won't stay running in that condition then you have an ignition problem, not a truck wiring problem. Either the condenser died or possibly the coil failed or you have a wiring problem between them. I've seen the wire that runs to the points get shorted to ground when the vacuum advance pulls in. With the power off and the points closed read the resistance from the point's wire to the batt -. It should be nearly 0 ohms. Draw a vacuum on the advance (suck on the hose) and see if it changes. The condenser comes into play when the points open. I forget how to troubleshoot it. I usually just toss another in it's place and see if the conditions change.

[gbass82]

Thanks for the help Ranchero50. I'll give that a shot. I'm thinking long and hard about a Pertronix unit.

[gbass82]

Well, my Fluke multimeter decided that it had enough yesterday and it quit on me so I couldn't get an Ohms reading. I went ahead and ordered a Pertronix ignitor unit. Once it comes in and I get it installed, I'll update you. Should I have purchased the Pertronix ignition coil as well or does it not make much of a difference?

[Ren]

You say the coil was replaced prior to the issue you are having now. If you still have the old coil, try it out.

My understanding of coils is there are two different types: 'Internal' and 'external' resisted. Internals read about 2.5 ohms. Externals read about 0.6 ohms.
I believe the purpose of resistance is to prevent the coil from overheating.

Our beloved trucks came from the factory externally resisted by the mysterious and often misunderstood 'ballast resistor' wire that hides under the dash. It functions by allowing 12 v to pass to the coil when it's cold. As the ignition system warms up, it drops current to around 8 v or so. This is to allow a strong spark when the engine is cold, and a weaker spark as the engine warms up. And thus, preventing overheating of ignition components. Some folks say it's pink in color. Other folks say that over time they fail. Either way, I don't think I like them. And I have no interest rooting around under my dash disturbing 50 YO wires. So I bypassed mine by disconnecting the + wire from the coil, leaving it hang, and running a new wire from the ignition switch to the coil.

Regarding the basic Pertronix unit: If you intend to omit or bypass the ballast resistor, you should use a 2.5 ohm coil. If you leave it in the circuit, get an 0.5 ohm coil. I suspect that the combination of a ballast resistor and a 2.5 ohm coil would cause a weak spark.

The Pertronix II is very different. It recommends bypassing the ballast resistor AND using an 0.6 ohm coil. The instructions very plainly state this and promise that no problems will occur. That is what I have in my truck, and that is what I did. Several thousand miles later, I've had no trouble. And my coil never seems unusually hot to the touch.

[gbass82]

Thanks for the good info Ren. I'll keep that in mind.