The 70 Mav and 72 Comet have been in the garage most of the past 3 years. I start them regularly and actually took the Mav out for a couple of rides recently and everything was fine until last weekend. I went out to fire it up and had some trouble. I have an ignition problem that I thought I got rid of 3 years ago, but it's now returned. I'm not getting any ignition spark until I release the key from the start position to the off position, it will fire for a brief second. It's similar to after burn but it's always a brief mis fire that never continues on like after burn would. Of course it will not remain running because the key is in the off position. It usually starts after going through this procedure several times but will often die and stall a time or two before warming up and then runs fine. I have a Dura spark system on my 302. The key ignition switch is the older type on the dash tray instead of the steering column. I suspect its that switch causing the problem. In the past I corrected it by tightening my coil connections and messing with the connection leading from ignition switch. I not certain either of those attempts actually solved any thing but the problem did seem to disappear. I just remembered I had the same problem years ago with the same car. But then I had a 289 in it with older non electronic ignition. I't seems it comes from the car sitting idle for long periods of time. It won't start at all today and I think it's time I solved this problem. I don't mind buying a new switch if I could say for sure it needs replacing. Any ideas??
Do you have another module you can try on it? I had that same problem once and as I remember, that's what it was. The switch is easy to test. Use a backup lamp bulb. Ground the base and touch the contact to the + on the coil with the key on and the bulb should light. It draws enough power to see if the switch is working reliably. You can also do this test with the switch in the start position too. It should light there as well.
I pulled the ignition switch, pulled it apart,visually checked the contacts and re-installed it. Measured the voltage with key on, 12 volts present. Then pulled all the connectors apart coming and going to and from the dura spark unit. They are looking a little old and worn, but still look good except I can see cooper on the red wire coming from the ignition switch as it enters the quick connector on the Dura spark module. Put my jumper switch on the selnoid relay, pulled the coil wire off and checked for spark and had spark. Went inside the car, turned the key and it fired up. ??? I'm not convinced it's my ignition switch yet. Next time it happens, I will check for voltage at the coil before I tear everything apart and re- install it. And I suppose I should be getting 12 volts during cranking also?? Does anybody know if that assumption is correct. I read about somebody adjusting their dash mounted ignition switch. Anyone know about that. I was thinking it may be my coil, but once it starts, it's fine no matter how long I drive or heat it up. I'll keep you posted and would appreciate any feedback.
Okay, I just when back out in the garage to check it and it started twice but not on the third try. Only 5 volts at the coil?? The test light brightens up during cranking so I think it must be getting 12 volts but will not fire. I'm going back out to fool with it.
8v at +coil during cranking, If I pull the connector on the Dura Spark coming from the ignition, I then get 12v at the + coil with key on. I think I'll pull the ignition switch again. Is there a way to bench test the switch?
I would check the voltage across the battery terminals while cranking. Could be the battery isn't delivering 12V under load.
