The Stovebolt Site Forums The Shop Area Engine Shop No spark

Hey guys! As you can tell, I'm new, but have been a lurker here for a few months. Sorry this post is so long, but I wanted to give some details as to what I've already done. I've got a problem that I can't figure out, and am hoping that some of you mechanical gurus can get me fixed up.

1948 Chevy 4100. I bought this truck about a month ago "irwipi" years ago, and naturally doesn't start now. After tinkering under the hood a bit, giving it a complete tune up and disassembling the carb(cleaning all the crap out of it). I hit the starter last week and she fired right up. I let it run for about an hour or so and it actually runs pretty darn good. I shut the engine off a few times, made sure it would restart. I was happy as a clam. My old beast runs.

Now to the bad news. When I shut it off for the night, that seems to be all she wrote. I went out the next day to start it so the oil could warm up a bit and I could change the oil. Now it doesn't start. I've tried everything that I can think of, and bottom line is that I'm not getting any spark. It cranks just fine... just no fire. I've doublechecked all connections. I'm getting 6v to the switch, ammeter, starter button, starter, coil, distributor. Any help would be greatly appreciated as to what my next step should be. I'll try to answer any questions as best as I can.

Thanks!
Chris

My '65 has just developed the exact same problem. I have been chasing this baby for a couple days now, I think I am going to get new points and a condensor, maybe a cap and rotor too. I put on new plug wires last year. I have power to the coil, I have checked all the wiring, tried a different coil and it still didn't work, so that pretty much leaves the distributor at fault. I cleaned and gapped the points(they are getting a bit worn out) and still no luck. So I guess a trip to Car Quest is in order. Maybe someone else has some suggestions too. I would really like to get this fixed.

Aaron

First question,,,,, do you have fire at the points?

I have tried getting spark off the coil and also by opening the points by hand and still got nothing. Since the last post, I tried a different condensor with no results. Even though the points are old, they are still opening fine and are gapped to about .017. I have checked all the wires to make sure they all have continuity. Tomorrow I am going to see if the distributor body is grounded to the engine, that's about all I have left. Whatever it is, it came on real sudden. It was running fine the other day and then it just wouldn't start.

Aaron

Check your ground wires to the engine block, namely the little straps from the firewall to the valve covers. These typically get left off after the rocker cover has been off for a valve adjustment or a new gasket.

Or, you may have a direct ground to the engine from the battery (good cranking), but a poor ground to the cab from the battery (low voltage to the coil).

Check it out and let us know, we are curious .

Put a matchbook cover between the points (that's how we used to gap them in emergencies) and see if you have 6 volts at the points. If you do, see if you have ground on the other side. If the + side of the coil has six volts on it, it has to be either the wire to the points, the points themselves or the ground to the points.

All the points are is an intermittent switch. When they're open, the hot side has 6 volts and the other side has 0 volts. When they're closed, both sides have 0 volts. You should be able to open and close the points with a non-conductor (popsicle stick does fine) and see a spark between them as you open them. If you don't, you're not getting voltage to the points or they're not grounded.

The points opening and closing builds up a field in the coil and then collapses it. If the coil is good, you should be able to connect a wire to ground and then brush it across the - side of the coil and get spark from the coil's center wire (pull it out of the distributor cap and hang it close to the engine (ground). If you brush that wire on the - side of the coil and it doesn't snap a spark to the engine, either the coil is bad or the coil wire is bad.

Hope this helps some.

I tried getting the points to spark by opening them by hand and got nothing. I checked to see if they were grounding to the distributor and they were, but I didn't think to check from the distributor body to the engine. I am betting on that right now. I hope that's what it is because that is really easy to fix. By the way, this is a 307 small-block with an Accel dual-point distributor and Accel Super Coil. My battery ground goes to the exhaust manifold but I do have a ground strap from the engine to frame and from frame to body.

Just checking,,,,, you are checking for fire at the points with the key in the "On" position?
I am suspecting the coil but other possibilities are not ruled out.

Wow! Thanks for the quick replies. If it quits raining here, I'm going to go out and check this stuff. I have a feeling (judging by some of the slipshod wiring in this truck over the last 50 years) that it's a simple ground issue. I'm pretty certain that I do not have fire at the points, but will doublecheck that too. It makes perfect sense that while tinkering under the hood, I bumped something just enough for it to make contact (thus, the truck started) ... and now whatever it is has come loose again. Ah well, just another excuse for me to get my mulitmeter out and put it to good use.

I'll post an update tomorrow hopefully, but it may be Monday before the rain moves out...

Many, many thanks to you guys!
Chris <-- anxious to get this beast back on the road

Well, I did some testing today. I checked to make sure everything that is supposed to be grounded and it all is. I am getting .2 volts across the points when they are open and the key is on. I unhooked the negative side of the coil and I also get .2 volts between the negative side and ground. I am getting 12 volts into the coil from the ballast resistor. This pretty much leads me to believe that it is the coil. I tried touching the negative wire from the coil to ground while holding the high tension coil wire near ground and got nothing when the key was turned on. So why do you think a coil would suddenly go bad while the truck was sitting still? Will the same thing happen to a new coil if I put one on?

Aaron

65chevyc20, you definitely have a bad coil. Why it went bad is anybody's guess. I doubt it would happen twice, so just buy a new coil and replace the defective on, and you should be on the road again.

Hey 65chevyc20! Next time try posting your own question. It is much more considerate.

Thanks for all the input guys. Just for the record, I came on here yesterday to post my own question but noticed that there was already one dealing with the same topic. I figured any suggestions could apply to anyone and as long as there is some flow of information I see no harm done. No point having multiple threads on the same topic.

Aaron

IT LIVES!!!

Okay, I think it was a combination of things, but namely one thing I will now never forget.

I think there may have been a bad ground off the battery. I replaced the (original) battery cables last week, and that helped more than you can imagine. The engine actually spins *fast* now.

The reason I was not getting fire at the points was because I didn't pay attention when I changed the points. I grounded the copper lead instead of sending it to the hot side of the coil. A simple 2 second fix. I put it all back together, turned the ignition switch and hit the starter. The old beast came to life instantly! I was actually quite surprised at how quickly it started.

Thanks again for everyone's help. It is truly appreciated, and I've got a few more "dumb" questions to ask before I get this truck roadworthy again. Now I can go change the oil like I had planned on doing last week... lol

Chris

Hey, blue48, that's great news! Glad you got the problem solved.